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Mucus escape reaction that involves the mandible
M u c u s escape reaction that involves the mandible A case report and diagnostic imaging considerations Tadahiko Kawai, DDS, PhD, a Shumei Murakami, DDS, PhD, a Takashi Maeda, DDS, a Mitsunobu Kishino, DDS, b and Kayoko Amino, DDS, PhD, c Osaka, Japan OSAKA UNIVERSITY, FACULTY OF DENTISTRY
We present a case of mucus escape reaction in which we encountered difficulty in interpreting the images acquired by plain radiography, computed tomography, and magnetic resonance imaging. The 48-year-old male Japanese patient was referred for evaluation of a gradual swelling subjacent to the inferior border of the left mandible. At the early imaging examinations, magnetic resonance imaging provided information crucial to resolving the issue of whether the lesion consisted of a central malignant disease process or a malignant disease in the submandibular space or both of these two separate disease entities. Magnetic resonance imaging demonstrated no evidence of tumorous lesion, but rather showed a fluid-containing cavity that was also confirmed by the subsequent intrasurgical inspection. On further consideration of these imaging findings, we concluded that the entity was mucus escape reaction with simultaneous occurrence of an intraconnective tissue hemorrhage adjacent to the left submandibulargland, concomitant extensive bony defect of the left mandible and lingual cortical defect, and chronic sialoadenitis of the left submandibular gland. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;83:408-15)
Making a precise image-based diagnosis before any surgical procedure is essential not only in terms of the early surgical approach and treatment schedule, but also to foster the postsurgical recovery of the patient, particularly in the case of a malignant disease. However, there are occasions in which it is difficult to formulate a diagnosis in advance of any surgical procedures, especially when the patient is affected by more than one disease entity. Most malignant cystic salivary gland tumors such as low-grade malignant mucoepidermoid carcinoma and acinic cell carcinoma usually do not present typical malignant features that would serve to obviously distinguish them from benign tumors or cysts arising from the salivary gland. 1,2 Therefore we have encountered some difficulties in determining whether diseases in the submandibular space are of benign or malignant character when our diagnostic evaluation was confined solely to clinical and imaging examinations. 1-7 Accordingly, we consider that such diseases usually cannot be definitively diagnosed until after the histologic examination or laboratory test has been performed. This is a dilemma common to all the radiodiagnosticians who are responsible for the provision of accurate imaging diagnoses to surgeons before surgical intervention. aDepartment of Oral and Maxillofacial Radiology. bClinical Laboratory. C2nd Department of Oral and Maxillofacial Surgery. Received for publication Apr. 1, 1996; returned for revision June 26, 1996; accepted for publication July 28, 1996. Copyright © 1997 by Mosby-Year Book, Inc. 1079-2104/97/$5.00 + 0 7116/77092
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Fig. 1. Sialographs reveal filling defect of left submandibular gland (arrow). Upper salivary lobe is compressed superoanteriorly, and lower lobe is compressed interoanteriorly.
The present case report describes a case in which diagnosis was difficult and in which magnetic resonance imaging (MRI) played the most important role in formulating an acceptable image-based diagnostic interpretation. In this rare case of mucus escape reaction (MER) associated with the left submandibular gland, concomitant lingual cortical defect and simple bone cyst were also present. The usefulness of MRI for distinguishing cysts from tumors accompanying a cystic lesion before surgery is emphasized.
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Fig. 2. Section of panoramic view displays well-definedextensive osteolydc lesion in left lower jaw (arrowheads). The lesion does not represent an expansive feature as a whole but scallops the inferior cortical plate inferiorily.
Fig. 4. Enhanced CT image shows homogeneous mass lesion (arrow).
Fig. 3. CT images demonstrate lingual cortical defect of the left lower jaw: A, axial view; B~ coronal view. CASE REPORT A 48-year-old male Japanese patient was referred to our hospital on December 7, 1994, from an Ear-Nose-Throat (ENT) clinic where he had sought treatment because of the
gradual increase in the size of a swelling noted in November 1994. He had been under observation since April 1994 when a swelling subjacent to the inferior border of the left mandible had been noticed. On extraoral examination, the swelling was elastic and soft in consistency and seemed to be continuous with the inferior border of the left mandible on palpation. The overlying skin appeared normal in color and texture, but abnormal sensation was present in the left lower lip. The intraoral exmination did not produce any pathologic findings except that salivary flow was poor in quantity. Sialography of the left submandibular gland, which had already been performed at the ENT clinic, exhibited a filling defect of the gland, with one lobule displaced downward and the other upward (Fig. 1). There was normal
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Fig. 5. MRI images reveal fluid-containing cavity located between left submandibular gland and concavity of lingual cortical defect. No tumorous images are identified in any areas of the lesion. A, T1weighted (low signal intensity); B, T2-weighted (high signal intensity); C, fat-suppressed Tl-weighted (intermediate signal intensity); D, fat-suppressed, contrast-enhanced, Tl-weighted (intermediate signal intensity). ductal ramification, but the acinal portion of the gland demonstrated punctate features. At the first x-ray examination conducted in our hospital, radiographs were obtained in periapical, occlusal, panoramic, and posteroanterior skull views. These demonstrated an extensive, unilocular, osteolytic lesion in the left lower jaw. The extensive radiolucency was almost entirely well demarcated, but partial disruption of the lesion margins was seen at the inferior border of the left mandible (Fig. 2). A malignant condition was suspected. On computed tomography (CT) scans, a lingual cortical defect of the left mandible (Fig. 3) and a homogeneous benign-appearing solid mass were identified (Fig. 4). The attenuation of the solid ovoid mass ranged from 10 to 20 in Hounsfield CT number, which indicated that it was a cystic lesion or a lesion composed of loose soft tissues. On the basis of these CT findings, we suspected the lesion to be a lingual cortical defect of the left mandible with a nonenhanced mass attached to the concavity of the bony defect (Fig. 4). On Tl-weighted MR images, the smooth ovoid mass showed a signal intensity slightly less than fat and higher signal intensity on T2-weighted images (Fig. 5). Three
minutes after intravenous injection of 15 ml of gadopentetate dimeglumine (Magnevist; Nihon Schering, Osaka, Japan), we obtained Tl-weighted images with and without fat suppression. However, the fat suppression and the addition of contrast did not seem to change the intensity of the signal from the original Tl-weighted images. On the basis of these MRI findings, it was thought that a fluid-containing cavity had extruded from the left submandibular gland and extended into the concavity of lingual cortical defect (Fig. 6); no tumorous mass was identified in either the cavity or the left mandible (Fig. 5). Most parts of the extensive osteolytic area of the left mandible depicted on plain radiographs were occupied by the cystic mass, with an attenuation from 10 to 20 HU seen on CT images. The remainder of the osteolytic area without the cystic involvement showed low-signal intensity on Tl-weighted, proton density-weighted, and T2-weighted MR images obtained without enhancement. On the basis of these features, it could not be determined whether the part with extensive osteolysis but without cystic involvement consisted of altered marrow tissues or of fibrous tissues with inflammation, but it was evidently not composed of fluid or empty cavity,
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A twofold tentative diagnosis was made: (1) that the swelling was caused by a lesion of MER initiated from the left submandibular gland affected with chronic inflammation and (2) that the extensive osteolysis was due to simple bone cyst and lingual cortical defect, which might be caused by the MER lesion or might already have existed before the development of the MER lesion. Because the malignant condition suspected early in the examination was ruled out in advance of surgery, the patient underwent removal of the cavity and the left submandibular gland without additional treatment. Intraoperatively it was noted that the swelling consisted of a cystic cavity that was filled with brownish serous fluid and was separated from tl~e adjacent salivary gland by a very thin membrane-like structure. The cavity was also attached to the surface of the lingual cortical defect of the mandible. Chemical analyses of tile contents of the cystic cavity indicated total protein of 8.1 mg/dl, amylase 40 U/L, and 750 H for serum iron value; the contents contained more than three times the normal serum iron level. Histologic analysis of the excised materials disclosed sequestrum formation in tire tissues from the mandibular bone and chronic inflammation of the submandibular gland but no evidence of epithelial lining in the cavity wall (Figs. 7 and 8). At the present time, 8 months after removal of the cavity and the left submandibular gland, the patient's postsurgical course has been uneventful. Panoramic radiographs obtained 6 months postsurgically revealed no alteration of the site.
DISCUSSION In the present case, as has also occurred in other cases, we were confronted with difficulties in differentiation among complicated disease processes before surgical intervention. One of the features that made interpretation of images difficult was that the extensive osteolysis with inferior cortical plate disruption made the lesion appear malignant on plain radiographs. The filling defect and displacement of the submandibular gland on the sialographs added to the impression of malignancy. Subsequent CT scanning demonstrated the presence of a cyst-like lesion extending partly to the left mandible without thin cortical outlining, and partly to the submandibular space. However, because the attenuation of the cystic lesion indicated a slightly higher CT value than a usual cyst and because the margins of the lesion did not show any cystic walls of soft and bony tissues, we were not able to determine whether the lesion was a cyst or not. Because of flcds, we applied MRI as well to more clearly visualize the interface of the cystic lesion with the surrounding tissue. By this means we clarified that there were no tumorous tissues associated with the cystic lesion, which lacked cyst walls. Subsequently, problems arose as to the relationship
Fig. 6. Tl-weighted, fat-suppressed MR image with contrast enhancement. Cystic lesion extrudes left submandibular gland (B) and extends into the left mandible (A). between this cystic lesion and the extensive osteolysis in the body extending to the ramus of the left mandible, the relationship between the osteolysis and the disruption of the inferior cortical border, and the relationship between the cystic lesion and the filling defect and displacement of the left submandibular gland. We conjectured that several disease processes might coexist in the same region of the left mandible and the subjacent submandibular space. Finally, we used all of the clinical, histologic, and image diagnostic imaging data and arrived at the conclusion that the patient had at least four loci of distinct entities occurring simultaneously. One lesion focus in our patient was located in the submandibular space and presented submandibular gland displacement on sialographs; it appeared to consist of a cystic cavity on the basis of CT and MRI findings and the findings during surgery. MER in a
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Fig. 7. Hist•path•••gicappearance•f•eftsubmandibu•arg•andsh•wsinf•ammat•ryce••in••trati•n•acinic atrophy, and fibrosis. (Hematoxylin-eosin stain; original magnification x25.) major salivary gland is generally a far less common disease process than is MER in a minor salivary gland.i, 8-11 This entity is usually accompanied with a cystic cavity without epithelial lining and contains mucus fluid. 1,8-11 Clinically, when the lesion is located below or dissects through mylohyoid musculature, the swelling is located in the area of submandibular space and inferior border of the mandible. 1 The swelling in our patient was situated subjacent to the inferior border of the left mandible, which is not inconsistent with the feature of the MER lesion associated with submandibular gland. In addition, the cavity, which lacked an epithelial lining, could easily be distinguished from other cystic lesions situated in the submandibular space, such as cystic tumors arising from the salivary glands, mucoepidermoid carcinoma, acinic cell adenocarcinoma, and lymphoepithelial cyst, and from tree cysts including submandibular hydatid cyst and mucus retention cyst. Ms In our case, the brownish serous fluid of the cavity, however, was not compatible with that in MER in terms of color and viscosity)' 8-11, 17 The analysis of long-standing .extravasated fluid may not reflect the initial nature of the fluid. In addition, the analysis of the contents of the cavity did n o t disclose high amylase activity, nor did the materials from the cavity wall show positive reaction to special stain for mucin, although strong staining with Berlin-blue was seen. Accordingly, it is unknown whether the contents of the cavity might have formed as a result of
MER. However, it is not possible that the cystic lesion was caused simply by a hematoma because it had grown gradually. It is certain that the chemical components of the contents would have been influenced to some extent by a secondary infection, resulting in discoloration and alteration in the viscosity of the contents of the cavity because of the bleeding at the site. Another lesion focus, the extensive osteolysis in the body of the left mandible, presented the typical features of a simple bone cyst as well as those of a lesion with a low-grade malignancy. 2"7, 17 However, when disruption of a part of the interior border is taken into consideration, it is quite difficult to determine whether the lesion displayed a pattern characteristic of a secondarily inflamed simple bone cyst or of a low-grade malignant condition such as mucoepidermoid carcinoma or acinic cell carcinoma or other similar malignant conditions originating from the salivary gland. Without any apparent intraoral inflammatory sources and with the sialographic findings of filling defect of the left submandibular gland, disruption of the inferior border of the mandible easily misled us to suspect that a central malignant salivary gland tumor might be projecting into the submandibular space, or, alternatively, that a malignant tumor arising from the left submandibular gland might be invading the left mandible. However, the MR images of the extensive osteolytic area definitely revealed that the area was mostly occupied by the cystic cavity, not by tumor tissues, with some parts of
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Fig. 8. Histopathologic appearance of the cavity wall: A, cavity wall is composed of inflammatory granulation tissue and fibrous connective tissue without epithelial lining. (Hematoxylin-eosin stain; original magnification x25.) B, Cavity wall contains many hemosidedn pigments (Berlin-blue stain; x25). the osteolysis not occupied by the cystic cavity. In addition, it was confirmed histologically that the bony tissues surrounding the cavity were involved with an inflammatory process, which was evidenced by the existence of sequestra in the left mandible and also confirmed during surgery. Thus we needed to consider the possibility that disruption of the mandibular cortical plate was depicted because the area was involved with an inflammatory process of the adjacent salivary gland, directly or indirectly via the cystic cavity. Because the margins of the extensive osteolysis were mostly well defined with relatively Smooth outlines except for the disruption of the inferior border, the osteolysis might have been caused by simple bone cyst with another secondarily inflamed cyst. On the basis of these findings, we deduced that the destruction of the inferior border was not caused by a tumor of any type but by a cyst with inflammation. This might imply the concomitant occurrence of two
separate cysts, as does the separation of the osteolytic lesion from the cavity by a bony border confirmed at the subsequent surgical inspection and CT and MRI examinations. The third lesion focus, lingual cortical defect, has been interpreted as an entity associated with a major salivary gland or an ectopic salivary gland, 17, 19-21but the one in our patient was associated with a cavity without epithelial lining like that in psuedocysts such as extravasation mucoceles or MER. It is unknown whether the bony defect was formed by the MER itself or whether the MER developed between the salivary gland and the pre-existing defect, which might have formed previously in association with the left submandibular gland. The recent gradual increase of the swelling may indicate that the primary focus of the lesion was not located at the submandibular space from the initial occurrence. Taking into consideration that the cystic lesion already almost filled the exten-
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vity
(A)
ity
(B)
Fig. 9. Schematic drawings depicting modes of MER growth. A, Relationship between cyst and left mandible in present case. Arrows, a and b indicate pattern of growth of MER. Arrows, a ' and b' indicate the presumed growth directions. A r r o w b ' suggests that MER did not have potential to erode the cortical plate of the bone because the MER, without destroying the cortex of the mandible, grows into the submandibular space. B, Hypothetical relationship between a cyst and the mandible when the MER is presumed to have the potential to destroy or erode the cortical plate of bone. A r r o w c indicates the presumed growth direction of a MER with the potential to destroy the cortical plate. sive osteolytic area of the left mandible, we speculate that it grew out down to the submandibular space after it grew into the osteolytic area. To the best of our knowledge, however, there is no report of M E R with bone erosion or destruction of the cortical plate of the mandible. Even if M E R has the potential to destroy or erode cortical plate of bone, the cavity would not have shown the morphologic characteristics like that in our patient depicted in Fig. 9A but rather that shape shown in Fig. 9B. The pattern of growth reveals that the cystic lesion did not destroy or erode the cortical plate of the bone and expand into the submandibular space. In addition, the short duration of illness is not in accord with the extensive osteolysis being due simply to a benign cyst. Accordingly, the initiation of disruption in the inferior border is most likely due to a pre-existing Stafne's bone cavity. A thick cortical lining of the bony defect could have been absent be: cause of inflammation near the surface of the bony defect, as a result of erosion by secondary inflammation around the cavity presumably originating from chronic sialoadenitis of the left submandibular gland. In fact, CT and M R I has demonstrated inflammation as an area of elevated attenuation and elevated signal
intensity of the cyst content, with high water contents, attributed to the markedly proteinacious condition after repeated episodes of infection. 16 The punctate sialographic feature of the left submandibular gland in our patient is the fourth lesion focus, one of the characteristic features of sialoadenitis that is found together with the clinical feature of poor salivary flow. This were confirmed by the histologic examination revealing chronic inflammation in the left submandibular gland. The abnormal sensation of the left lower lip suggests an apparent involvement of the left mandibular canal. Although it is unlikely that the cyst itself caused the paresthesia, inflammation around the cyst could have stimulated the mandibular nerve as it traversed the osteolytic area. In conclusion, we speculate that a fluid-containing cystic lesion first developed near the pre-existing lingual cortical defect area; it then extended in one direction into the pre-existing simple bone cyst of the left mandible and in the other direction into the left submandibular gland and space. M R I and CT provided information that was essential to the management of this case.
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 83, Number 3 REFERENCES 1. Ellis GL, Auclair PL, Gnepp DR. Surgical pathology of the salivary glands. 1st ed. Philadelphia: WB Saunders, 1991:2638, 66-71. 2. Lopez JI, Elizalde JM, Landa S. Central mucoepidermoid carcinoma: report of a case and review of the literature. Pathol Res Pract 1993;189:365-7. 3. Ayudhya NSN, Parichatikanond P, Chinda K. Benign cystic teratorna of the parotid salivary gland: report of the first case in Thailand. J Meal Thai 1991;74:478-80. 4. Hirota J, Maeda Y~ Ueta E, Osaka T. Immunohistochemical and histologic study of cervical lymphoepithelial cysts. J Oral Pathol Med 1989;18:202-5. 5. Elliott JN, Oertel YC. Lymphoepitelial cysts of the salivary g.lands. Am J Clin Pathol 1990;93:39-43. 6. Oneric M, Turan E, Ruacan S. Submandibular hydatid cyst: a case report. J Craniomaxillofac Surg 1991 ;19:359-61. 7. Browand BC, Waldron CA. Central mucoepidermoid tumors of the jaws: report of nine cases and review of the literature. Oral Surg Oral Med Oral Pathol 1975;40:631-43. 8. Fein S, Mohnac AM. Submandibular gland extravasation cyst: report of an unusual case. J Oral Surg 1973;31:55l-2. 9. Harrison JD. Salivary mucoceles. Oral Surg Oral Med Oral Pathol 1975;39:268-78. 10. Bhaskar SN. Central mucoepidermoid tumors of the mandible: report of 2 cases. Cancer 1963;16:721-6. 11. Chaudhry AP, Reynolds DH, Lachapelle CF, Vickers RA. A clinical and experimental study of mucocele (Retention cyst). J Dent Res 1960;39:1253-62. 12. Stoch RB, Smith I. Mucoepidermoid carcinoma in the mandible: report of case. J Oral Surg 1980;38:56-8.
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13. Zafarulla MYM. Cervical mucocele (plunging ranula): an unusual case of mucous extravasation cyst. Oral Surg Oral Med Oral Pathol 1986;62:63-6. 14. Dhawan IK, Gupta RK. Central salivary gland tumors of jaw. Cancer 1970;26:211-7. 15. Brookstone MS, Huvos AG. Central salivery gland tumors of the maxilla and mandible: a clinicopathologic study of 11 cases with an analysis of the literacture. J Oral Maxillofac Surg 1992;50:229-36. 16. Som PM, Bergeron RT. Head and neck imaging. 2nd ed. St. Louis: Mosby Year Book, 1991:128-43,310-20. 17. Shafer WG, Hine MK, Levy BM. A textbook of oral pathology. 4th ed. Philadelphia: WB Saunders, 1983:557-61. 18. Stafne EC. Oral roentgenographic diagnosis. 3rd ed. Philadelphia: WB Saunders, 1969:111-2. 19. Stafne EC. Bone cavities situated near the angle of the mandible. J Am Dent Assoc 1942;29:1969-72. 20. Str~mn C, Fjellstr~Sm C-A. An unusual case of lingual mandibular depression. Oral Surg Oral Med Oral Pathol 1987;64: 159-61. 21. Barker GR. A radiolucency of the ascending ramus of the mandible associated with invested parotid salivary gland material and analogous with a Stafne bone cavity. Br J Oral Maxillofac Surg 1988;26:8l-4.
Reprint requests: Tadahiko Kawai, DDS, PhD Department of Oral and Maxillofacial Radiology Osaka University, Faculty of Dentistry 1-8, Yamadaoka, Suita, Osaka 565, Japan
American Academy of Oral and Maxillofacial Radiology Presents the Second Annual Arthur H. Wuehrmann Award In 1995 the American Academy of Oral and Maxillofacial Radiology initiated the Arthur H. Wuehrmann Award to honor both the first Editor of the Oral and Maxillofacial Radiology Section, Dr. Arthur H. Wuehrmann, and the article selected as the most notable contribution to Oral and Maxillofacial Radiology during the preceding two volumes of this Journal. The 1996 award, selected by the Editorial Board and reviewers of the Oral and Maxillofacial Radiology Section, was conferred on the article "Usefulness of tomography in the evaluation of patients with temporomandibular disorders: A retrospective clinical study," authored by Karla I. Callender and Sharon L. Brooks (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;81:710-9). After reviewing the records of 116 patients who had had tomograms made, the authors concluded that, based on their study, tomography had little effect on the diagnosis and management of patients with temporomandibular disorders.
We present a case of mucus escape reaction in which we encountered difficulty in interpreting the images acquired by plain radiography, computed tomography, and magnetic resonance imaging. The 48-year-old male Japanese patient was referred for evaluation of a gradual swelling subjacent to the inferior border of the left mandible. At the early imaging examinations, magnetic resonance imaging provided information crucial to resolving the issue of whether the lesion consisted of a central malignant disease process or a malignant disease in the submandibular space or both of these two separate disease entities. Magnetic resonance imaging demonstrated no evidence of tumorous lesion, but rather showed a fluid-containing cavity that was also confirmed by the subsequent intrasurgical inspection. On further consideration of these imaging findings, we concluded that the entity was mucus escape reaction with simultaneous occurrence of an intraconnective tissue hemorrhage adjacent to the left submandibulargland, concomitant extensive bony defect of the left mandible and lingual cortical defect, and chronic sialoadenitis of the left submandibular gland. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;83:408-15)
Making a precise image-based diagnosis before any surgical procedure is essential not only in terms of the early surgical approach and treatment schedule, but also to foster the postsurgical recovery of the patient, particularly in the case of a malignant disease. However, there are occasions in which it is difficult to formulate a diagnosis in advance of any surgical procedures, especially when the patient is affected by more than one disease entity. Most malignant cystic salivary gland tumors such as low-grade malignant mucoepidermoid carcinoma and acinic cell carcinoma usually do not present typical malignant features that would serve to obviously distinguish them from benign tumors or cysts arising from the salivary gland. 1,2 Therefore we have encountered some difficulties in determining whether diseases in the submandibular space are of benign or malignant character when our diagnostic evaluation was confined solely to clinical and imaging examinations. 1-7 Accordingly, we consider that such diseases usually cannot be definitively diagnosed until after the histologic examination or laboratory test has been performed. This is a dilemma common to all the radiodiagnosticians who are responsible for the provision of accurate imaging diagnoses to surgeons before surgical intervention. aDepartment of Oral and Maxillofacial Radiology. bClinical Laboratory. C2nd Department of Oral and Maxillofacial Surgery. Received for publication Apr. 1, 1996; returned for revision June 26, 1996; accepted for publication July 28, 1996. Copyright © 1997 by Mosby-Year Book, Inc. 1079-2104/97/$5.00 + 0 7116/77092
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Fig. 1. Sialographs reveal filling defect of left submandibular gland (arrow). Upper salivary lobe is compressed superoanteriorly, and lower lobe is compressed interoanteriorly.
The present case report describes a case in which diagnosis was difficult and in which magnetic resonance imaging (MRI) played the most important role in formulating an acceptable image-based diagnostic interpretation. In this rare case of mucus escape reaction (MER) associated with the left submandibular gland, concomitant lingual cortical defect and simple bone cyst were also present. The usefulness of MRI for distinguishing cysts from tumors accompanying a cystic lesion before surgery is emphasized.
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Fig. 2. Section of panoramic view displays well-definedextensive osteolydc lesion in left lower jaw (arrowheads). The lesion does not represent an expansive feature as a whole but scallops the inferior cortical plate inferiorily.
Fig. 4. Enhanced CT image shows homogeneous mass lesion (arrow).
Fig. 3. CT images demonstrate lingual cortical defect of the left lower jaw: A, axial view; B~ coronal view. CASE REPORT A 48-year-old male Japanese patient was referred to our hospital on December 7, 1994, from an Ear-Nose-Throat (ENT) clinic where he had sought treatment because of the
gradual increase in the size of a swelling noted in November 1994. He had been under observation since April 1994 when a swelling subjacent to the inferior border of the left mandible had been noticed. On extraoral examination, the swelling was elastic and soft in consistency and seemed to be continuous with the inferior border of the left mandible on palpation. The overlying skin appeared normal in color and texture, but abnormal sensation was present in the left lower lip. The intraoral exmination did not produce any pathologic findings except that salivary flow was poor in quantity. Sialography of the left submandibular gland, which had already been performed at the ENT clinic, exhibited a filling defect of the gland, with one lobule displaced downward and the other upward (Fig. 1). There was normal
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Fig. 5. MRI images reveal fluid-containing cavity located between left submandibular gland and concavity of lingual cortical defect. No tumorous images are identified in any areas of the lesion. A, T1weighted (low signal intensity); B, T2-weighted (high signal intensity); C, fat-suppressed Tl-weighted (intermediate signal intensity); D, fat-suppressed, contrast-enhanced, Tl-weighted (intermediate signal intensity). ductal ramification, but the acinal portion of the gland demonstrated punctate features. At the first x-ray examination conducted in our hospital, radiographs were obtained in periapical, occlusal, panoramic, and posteroanterior skull views. These demonstrated an extensive, unilocular, osteolytic lesion in the left lower jaw. The extensive radiolucency was almost entirely well demarcated, but partial disruption of the lesion margins was seen at the inferior border of the left mandible (Fig. 2). A malignant condition was suspected. On computed tomography (CT) scans, a lingual cortical defect of the left mandible (Fig. 3) and a homogeneous benign-appearing solid mass were identified (Fig. 4). The attenuation of the solid ovoid mass ranged from 10 to 20 in Hounsfield CT number, which indicated that it was a cystic lesion or a lesion composed of loose soft tissues. On the basis of these CT findings, we suspected the lesion to be a lingual cortical defect of the left mandible with a nonenhanced mass attached to the concavity of the bony defect (Fig. 4). On Tl-weighted MR images, the smooth ovoid mass showed a signal intensity slightly less than fat and higher signal intensity on T2-weighted images (Fig. 5). Three
minutes after intravenous injection of 15 ml of gadopentetate dimeglumine (Magnevist; Nihon Schering, Osaka, Japan), we obtained Tl-weighted images with and without fat suppression. However, the fat suppression and the addition of contrast did not seem to change the intensity of the signal from the original Tl-weighted images. On the basis of these MRI findings, it was thought that a fluid-containing cavity had extruded from the left submandibular gland and extended into the concavity of lingual cortical defect (Fig. 6); no tumorous mass was identified in either the cavity or the left mandible (Fig. 5). Most parts of the extensive osteolytic area of the left mandible depicted on plain radiographs were occupied by the cystic mass, with an attenuation from 10 to 20 HU seen on CT images. The remainder of the osteolytic area without the cystic involvement showed low-signal intensity on Tl-weighted, proton density-weighted, and T2-weighted MR images obtained without enhancement. On the basis of these features, it could not be determined whether the part with extensive osteolysis but without cystic involvement consisted of altered marrow tissues or of fibrous tissues with inflammation, but it was evidently not composed of fluid or empty cavity,
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A twofold tentative diagnosis was made: (1) that the swelling was caused by a lesion of MER initiated from the left submandibular gland affected with chronic inflammation and (2) that the extensive osteolysis was due to simple bone cyst and lingual cortical defect, which might be caused by the MER lesion or might already have existed before the development of the MER lesion. Because the malignant condition suspected early in the examination was ruled out in advance of surgery, the patient underwent removal of the cavity and the left submandibular gland without additional treatment. Intraoperatively it was noted that the swelling consisted of a cystic cavity that was filled with brownish serous fluid and was separated from tl~e adjacent salivary gland by a very thin membrane-like structure. The cavity was also attached to the surface of the lingual cortical defect of the mandible. Chemical analyses of tile contents of the cystic cavity indicated total protein of 8.1 mg/dl, amylase 40 U/L, and 750 H for serum iron value; the contents contained more than three times the normal serum iron level. Histologic analysis of the excised materials disclosed sequestrum formation in tire tissues from the mandibular bone and chronic inflammation of the submandibular gland but no evidence of epithelial lining in the cavity wall (Figs. 7 and 8). At the present time, 8 months after removal of the cavity and the left submandibular gland, the patient's postsurgical course has been uneventful. Panoramic radiographs obtained 6 months postsurgically revealed no alteration of the site.
DISCUSSION In the present case, as has also occurred in other cases, we were confronted with difficulties in differentiation among complicated disease processes before surgical intervention. One of the features that made interpretation of images difficult was that the extensive osteolysis with inferior cortical plate disruption made the lesion appear malignant on plain radiographs. The filling defect and displacement of the submandibular gland on the sialographs added to the impression of malignancy. Subsequent CT scanning demonstrated the presence of a cyst-like lesion extending partly to the left mandible without thin cortical outlining, and partly to the submandibular space. However, because the attenuation of the cystic lesion indicated a slightly higher CT value than a usual cyst and because the margins of the lesion did not show any cystic walls of soft and bony tissues, we were not able to determine whether the lesion was a cyst or not. Because of flcds, we applied MRI as well to more clearly visualize the interface of the cystic lesion with the surrounding tissue. By this means we clarified that there were no tumorous tissues associated with the cystic lesion, which lacked cyst walls. Subsequently, problems arose as to the relationship
Fig. 6. Tl-weighted, fat-suppressed MR image with contrast enhancement. Cystic lesion extrudes left submandibular gland (B) and extends into the left mandible (A). between this cystic lesion and the extensive osteolysis in the body extending to the ramus of the left mandible, the relationship between the osteolysis and the disruption of the inferior cortical border, and the relationship between the cystic lesion and the filling defect and displacement of the left submandibular gland. We conjectured that several disease processes might coexist in the same region of the left mandible and the subjacent submandibular space. Finally, we used all of the clinical, histologic, and image diagnostic imaging data and arrived at the conclusion that the patient had at least four loci of distinct entities occurring simultaneously. One lesion focus in our patient was located in the submandibular space and presented submandibular gland displacement on sialographs; it appeared to consist of a cystic cavity on the basis of CT and MRI findings and the findings during surgery. MER in a
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Fig. 7. Hist•path•••gicappearance•f•eftsubmandibu•arg•andsh•wsinf•ammat•ryce••in••trati•n•acinic atrophy, and fibrosis. (Hematoxylin-eosin stain; original magnification x25.) major salivary gland is generally a far less common disease process than is MER in a minor salivary gland.i, 8-11 This entity is usually accompanied with a cystic cavity without epithelial lining and contains mucus fluid. 1,8-11 Clinically, when the lesion is located below or dissects through mylohyoid musculature, the swelling is located in the area of submandibular space and inferior border of the mandible. 1 The swelling in our patient was situated subjacent to the inferior border of the left mandible, which is not inconsistent with the feature of the MER lesion associated with submandibular gland. In addition, the cavity, which lacked an epithelial lining, could easily be distinguished from other cystic lesions situated in the submandibular space, such as cystic tumors arising from the salivary glands, mucoepidermoid carcinoma, acinic cell adenocarcinoma, and lymphoepithelial cyst, and from tree cysts including submandibular hydatid cyst and mucus retention cyst. Ms In our case, the brownish serous fluid of the cavity, however, was not compatible with that in MER in terms of color and viscosity)' 8-11, 17 The analysis of long-standing .extravasated fluid may not reflect the initial nature of the fluid. In addition, the analysis of the contents of the cavity did n o t disclose high amylase activity, nor did the materials from the cavity wall show positive reaction to special stain for mucin, although strong staining with Berlin-blue was seen. Accordingly, it is unknown whether the contents of the cavity might have formed as a result of
MER. However, it is not possible that the cystic lesion was caused simply by a hematoma because it had grown gradually. It is certain that the chemical components of the contents would have been influenced to some extent by a secondary infection, resulting in discoloration and alteration in the viscosity of the contents of the cavity because of the bleeding at the site. Another lesion focus, the extensive osteolysis in the body of the left mandible, presented the typical features of a simple bone cyst as well as those of a lesion with a low-grade malignancy. 2"7, 17 However, when disruption of a part of the interior border is taken into consideration, it is quite difficult to determine whether the lesion displayed a pattern characteristic of a secondarily inflamed simple bone cyst or of a low-grade malignant condition such as mucoepidermoid carcinoma or acinic cell carcinoma or other similar malignant conditions originating from the salivary gland. Without any apparent intraoral inflammatory sources and with the sialographic findings of filling defect of the left submandibular gland, disruption of the inferior border of the mandible easily misled us to suspect that a central malignant salivary gland tumor might be projecting into the submandibular space, or, alternatively, that a malignant tumor arising from the left submandibular gland might be invading the left mandible. However, the MR images of the extensive osteolytic area definitely revealed that the area was mostly occupied by the cystic cavity, not by tumor tissues, with some parts of
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Fig. 8. Histopathologic appearance of the cavity wall: A, cavity wall is composed of inflammatory granulation tissue and fibrous connective tissue without epithelial lining. (Hematoxylin-eosin stain; original magnification x25.) B, Cavity wall contains many hemosidedn pigments (Berlin-blue stain; x25). the osteolysis not occupied by the cystic cavity. In addition, it was confirmed histologically that the bony tissues surrounding the cavity were involved with an inflammatory process, which was evidenced by the existence of sequestra in the left mandible and also confirmed during surgery. Thus we needed to consider the possibility that disruption of the mandibular cortical plate was depicted because the area was involved with an inflammatory process of the adjacent salivary gland, directly or indirectly via the cystic cavity. Because the margins of the extensive osteolysis were mostly well defined with relatively Smooth outlines except for the disruption of the inferior border, the osteolysis might have been caused by simple bone cyst with another secondarily inflamed cyst. On the basis of these findings, we deduced that the destruction of the inferior border was not caused by a tumor of any type but by a cyst with inflammation. This might imply the concomitant occurrence of two
separate cysts, as does the separation of the osteolytic lesion from the cavity by a bony border confirmed at the subsequent surgical inspection and CT and MRI examinations. The third lesion focus, lingual cortical defect, has been interpreted as an entity associated with a major salivary gland or an ectopic salivary gland, 17, 19-21but the one in our patient was associated with a cavity without epithelial lining like that in psuedocysts such as extravasation mucoceles or MER. It is unknown whether the bony defect was formed by the MER itself or whether the MER developed between the salivary gland and the pre-existing defect, which might have formed previously in association with the left submandibular gland. The recent gradual increase of the swelling may indicate that the primary focus of the lesion was not located at the submandibular space from the initial occurrence. Taking into consideration that the cystic lesion already almost filled the exten-
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(A)
ity
(B)
Fig. 9. Schematic drawings depicting modes of MER growth. A, Relationship between cyst and left mandible in present case. Arrows, a and b indicate pattern of growth of MER. Arrows, a ' and b' indicate the presumed growth directions. A r r o w b ' suggests that MER did not have potential to erode the cortical plate of the bone because the MER, without destroying the cortex of the mandible, grows into the submandibular space. B, Hypothetical relationship between a cyst and the mandible when the MER is presumed to have the potential to destroy or erode the cortical plate of bone. A r r o w c indicates the presumed growth direction of a MER with the potential to destroy the cortical plate. sive osteolytic area of the left mandible, we speculate that it grew out down to the submandibular space after it grew into the osteolytic area. To the best of our knowledge, however, there is no report of M E R with bone erosion or destruction of the cortical plate of the mandible. Even if M E R has the potential to destroy or erode cortical plate of bone, the cavity would not have shown the morphologic characteristics like that in our patient depicted in Fig. 9A but rather that shape shown in Fig. 9B. The pattern of growth reveals that the cystic lesion did not destroy or erode the cortical plate of the bone and expand into the submandibular space. In addition, the short duration of illness is not in accord with the extensive osteolysis being due simply to a benign cyst. Accordingly, the initiation of disruption in the inferior border is most likely due to a pre-existing Stafne's bone cavity. A thick cortical lining of the bony defect could have been absent be: cause of inflammation near the surface of the bony defect, as a result of erosion by secondary inflammation around the cavity presumably originating from chronic sialoadenitis of the left submandibular gland. In fact, CT and M R I has demonstrated inflammation as an area of elevated attenuation and elevated signal
intensity of the cyst content, with high water contents, attributed to the markedly proteinacious condition after repeated episodes of infection. 16 The punctate sialographic feature of the left submandibular gland in our patient is the fourth lesion focus, one of the characteristic features of sialoadenitis that is found together with the clinical feature of poor salivary flow. This were confirmed by the histologic examination revealing chronic inflammation in the left submandibular gland. The abnormal sensation of the left lower lip suggests an apparent involvement of the left mandibular canal. Although it is unlikely that the cyst itself caused the paresthesia, inflammation around the cyst could have stimulated the mandibular nerve as it traversed the osteolytic area. In conclusion, we speculate that a fluid-containing cystic lesion first developed near the pre-existing lingual cortical defect area; it then extended in one direction into the pre-existing simple bone cyst of the left mandible and in the other direction into the left submandibular gland and space. M R I and CT provided information that was essential to the management of this case.
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13. Zafarulla MYM. Cervical mucocele (plunging ranula): an unusual case of mucous extravasation cyst. Oral Surg Oral Med Oral Pathol 1986;62:63-6. 14. Dhawan IK, Gupta RK. Central salivary gland tumors of jaw. Cancer 1970;26:211-7. 15. Brookstone MS, Huvos AG. Central salivery gland tumors of the maxilla and mandible: a clinicopathologic study of 11 cases with an analysis of the literacture. J Oral Maxillofac Surg 1992;50:229-36. 16. Som PM, Bergeron RT. Head and neck imaging. 2nd ed. St. Louis: Mosby Year Book, 1991:128-43,310-20. 17. Shafer WG, Hine MK, Levy BM. A textbook of oral pathology. 4th ed. Philadelphia: WB Saunders, 1983:557-61. 18. Stafne EC. Oral roentgenographic diagnosis. 3rd ed. Philadelphia: WB Saunders, 1969:111-2. 19. Stafne EC. Bone cavities situated near the angle of the mandible. J Am Dent Assoc 1942;29:1969-72. 20. Str~mn C, Fjellstr~Sm C-A. An unusual case of lingual mandibular depression. Oral Surg Oral Med Oral Pathol 1987;64: 159-61. 21. Barker GR. A radiolucency of the ascending ramus of the mandible associated with invested parotid salivary gland material and analogous with a Stafne bone cavity. Br J Oral Maxillofac Surg 1988;26:8l-4.
Reprint requests: Tadahiko Kawai, DDS, PhD Department of Oral and Maxillofacial Radiology Osaka University, Faculty of Dentistry 1-8, Yamadaoka, Suita, Osaka 565, Japan
American Academy of Oral and Maxillofacial Radiology Presents the Second Annual Arthur H. Wuehrmann Award In 1995 the American Academy of Oral and Maxillofacial Radiology initiated the Arthur H. Wuehrmann Award to honor both the first Editor of the Oral and Maxillofacial Radiology Section, Dr. Arthur H. Wuehrmann, and the article selected as the most notable contribution to Oral and Maxillofacial Radiology during the preceding two volumes of this Journal. The 1996 award, selected by the Editorial Board and reviewers of the Oral and Maxillofacial Radiology Section, was conferred on the article "Usefulness of tomography in the evaluation of patients with temporomandibular disorders: A retrospective clinical study," authored by Karla I. Callender and Sharon L. Brooks (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;81:710-9). After reviewing the records of 116 patients who had had tomograms made, the authors concluded that, based on their study, tomography had little effect on the diagnosis and management of patients with temporomandibular disorders.