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The human accessory parotid gland: Its incidence, nature, and significance
The human accessory parotid gland: Its incidence, nature, and significance Jack Prommer, SCHOOLS
OF
Ph.D.,*
MEDICINE
AND
Boston, DENTAL
Mass. MEDICINE,
TUFTS
UNIVERSITY
Dissections of human parotid glands were undertaken to observe the incidence, size, location, and histologic characteristics of accessory parotid glands. These data were related to the premise that an unusual location and appearance of the accessory gland might preclude complete surgical removal of a parotid tumor. This, in turn, could be a factor in the high recurrence rate after apparently total excision of benign mixed tumors of the parotid gland.
0
perations on the parotid gland involve difficulties not often encountered elsewhere by the general surge0n.l Not the least of these surgical obstacles is the “sandwich-like” or “lattice-like” arrangement of parts of the facial nerve within the glandular mass.2-8 Another difficulty is that of visualizing and removing all extensions of the widely ramifying gland, particularly the deep, retromandibular portion projecting toward the lateral pharyngeal space.l Appreciation of these aspects of parotid anatomy is important not only for the prevention of nerve damage during partial or complete parotidectomies, but also for making reasonably certain that the parotid tumors are completely removed during the operation.6 In spite of this knowledge of the surgical anatomy of the parotid gland, surgeons are occasionally faced with tumor recurrence, especially after excision of benign mixed tumors, which make up the greatest percentage of parotid tumors. An additional morphologic feature, the accessory parotid gland, warrants further study in this context. The observation of accessory glands which were quite far removed from the main gland made it seem evident that this separation from a principal surgical site might preclude the complete removal of a tumor and thus might be a cause of tumor recurrence. Many textbooks and journal articles mention an accessory parotid gland and A portion of this paper was presented at the eighty-eighth Association of Anatomists, Los Angeles, Calif., March, 1975; “Professor, Department of Anatomy.
annual
session
of the American
671
672
Pronww~
Fig. 1. Three variations at the anterior rstcnsion. B, Attached anterior extension mass or “accessory parotid gland” (APG).
border of the parotid gland (PC). A, No anterior or “facial process” (FP). C, Detached glandular
describe it in variable ways, but only one major report considers the clinicopathologic aspects and surgical management of it.” These investigators recognized that a swelling in the soft part of the cheek may represent a tumor of the “accessory parotid apparatus.” In their description of a special surgical approach in twenty patients who were suspected of having preauricular tumors in this region, they found that eleven of the twenty did have some form of lesion of the acessory parotid “area.” Anderson and Byarsl stated that benign parotid tumors may be found anywhere in the gland, including “far out on the cheek in the accessory portion.” The purpose of the present investigation was to observe the incidence, size, location, and histologic features of accessory parotid glands, and to relate these data to possible involvement in the recurrence of parotid tumors. X-ray films and sialograms were studied to determine how well the accessory glands could bc visualized for diagnostic purposes. Histologic sections of the accessory parotid gland were compared with sections of the main gland to determine whether pathosis of the main gland could also involve the accessory gland by the same neoplastic process. If differences existed, it would not be so likely that the recurrence of a parotid tumor could be ascribed to the accessory gland. However, other pathoses of the accessory mass could occur independently of, and be unrelated to, the parotid gland proper. MATERIALS
AND
METHODS
Ninety-six dissections were studied on adult human cadavers of both sexes. The presence, size, location, and relationships of accessory parotid glands were noted. An essential criterion for identification of an accessory parotid gland was its complete detachment from the main body of the gland. An attached anterior extension of the main gland along the course of the parotid duct is a “facial process” and was not categorized as an accessory gland (Fig. 1). Eight accessory glands, each with a segment of the major parotid gland from
Volume Number
43 5
Fig. tionship
8. A selection of several to Stensen’s duct (SD).
Human
large
accessory
parotid
accessory
glands
(LUG).
parotid
Note
gland
673
the
rela-
close
the same facial half, were removed for histologic processing. After additional (postembalming) fixation for 1 week in 10 per cent neutral buffered formalin, paraffin sections were cut at 6 to 10 p and stained either with hematoxylin and eosin or with Mallory’s trichrome. X-ray films and sialograms from the teaching collection of the Department of Radiology at the Tufts-New England Medical Center Hospitals were examined for visualization of accessory parotid glands and their ducts. RESULTS
Twenty of the ninety-six dissections (21 per cent) revealed clearly detached accessory glands, of variable size, shape, and position. Most of them could bc described in familiar terms as ranging in size from a small flattened pea to a large lima bean. The flattened appearance was the result of their compression between the masseter muscle and the skin. The accessory gland was bound to the masseter muscle by an extension of the masseteric fascia. It was found in close relation to Stensen’s duct in the anterior course of the duct across the muscle, usually lying on or above the duct (Fig. 2). The accessory gland usually had one major tributary emptying into Stensen’s duct, but occasionally two or more were observed. The average distance of distinctly separated accessory glands from the anterior edge of the main gland was
Oral May,
surg. 1977
Fig. 3. Histologic section showing normal aging characteristics which appear in the accessory gland and the main glandular mass of the same facial half. Note the decreased glandular element?, the increased proportion of fat, and the increase in fibrous connective tissue. (Hematoxyhn and cosin stain. Original magnification, x100.)
6.0 mm. The farthest removed accessory gland rested on the buccal fat pad at the anterior border of the masseter muscle. Histologic comparisons of the accessory and main glands revealed no appreciable differences in either their acini or their duct systems. An increased proportion of fat, accompanied by a proportional decrease in glandular elements, was seen in many accessory and main glands (Fig. 3). This was considered to be a normal aging phenomenon, as was an increase in fibrous connective tissue. These aging changes were not more extensive in the accessory gland than in the main gland. Slight inflammatory changes, in the form of scattered lymphocytes and periductal lymphocytosis, were seen occasionally and were equally evident in both glandular masses Routine diagnostic x-ray films did not reveal accessory parotid glands. Sialograms, for the recording of which a contrast medium was used to fill the parotid duct and its tributaries, did successfully reveal the duct system of accessory parotid glands (Fig. 4). DISCUSSION In their anatomic study of the parotid gland, Winsten and Ward” noted that, “although the knowledge of the anatomy is not vital in itself, the possible influence it might have on the surgical approach to parotid neoplasms is considerable.” Since the early anatomic study by McWhorter,2 there has been an overwhelming number of investigations aimed at defining the complex relationship between the facial nerve and the parotid gland in order to reduce the hazards of operation in this region. Another line of extensive investigations studied the “parotid bed” in order to minimize the difficulty of visualizing and removing the entire gland, thus hopefully reducing the recurrence rate after tumor excision.‘, G For many years the possible clinical significance of a separate glandular mass, the accessory parotid gland, was overlooked. The major reasons for this were twofold: one was the preoccupation with the anatomy of the gland-nerve relation-
Volume Number
frzmau
43 5
Fig. 4. Sialoangiograms gland is clearly revealed. Accessory parotid gland.
in which Conventional PG, Parotid
accesson~ parotid
ghtd
675
the duct system of a widely separated accessory parotid radiograph on the left, a reversal on the right. apt, gland.
ship; the other was the differences of interpretation in identifying an accessory parotid gland. There is still not complete agreement among authors and investigators that an accessory parotid gland should be completely detached from the main body of the gland. It is not uncommon to find illustrations and descriptions in which an attached anterior portion, the “facial process,” is identified as an accessory parotid gland. A continuous facial process, not easily overlooked in a parotidectomy, was of no concern in the present study. Many accessory parotid glands are located close to the main gland and would not easily escape notice during an operation. However, the more widely removed ones could, indeed, be overlooked in the usual operative field and would require a more extensive preoperative diagnosis as well as a wider surgical field. It is difficult to distinguish accessory parotid glands or their ducts in routine diagnostic x-ray examinations. Sialograms, however, will usually reveal the duct system of an accessory gland, and thus enable a surgeon to plan a wider operative field for a parotidectomy when the major and accessory portions are involved.” Histologically, the accessory and the main parotid glands are similar. There were no appreciable differences in either the acini or the duct systems, which indicates a similar secretory activity of the accessory and main portions of the gland. The normal aging processes, including fatty infiltration and fibrotic changes with the accompanying loss of glandular tissue, occur equally in the accessory and main gland. Because of the similarity of microscopic structure, any pathoses involving the main gland could also involve the accessory gland. Thus, failure to remove a distantly separated accessory gland during parotidectomy could conceivably result in the appearance of a second tumor after removal of the primary one.
A thorough understanding of the anatomy of the parotid gland is nccessar~ for accurate interpretations of sialoangiogramsl” and for the development of new surgical approaches in the parotid area.” Improved techniques increase the probability of excision of distantly separated accessory parotid glands and thcrcby reduce the possibility of tumor recurrence after parotidectomy. SUMMARY
Observations on ninety-six dissections of human parotid glands have been presented, with the incidence, size, location, and histologic features of accessory parotid glands noted. Twenty-one per cent of the dissections revealed clearly detached accessory glands at variable distances from the main gland. There were no appreciable histopathologic differences between the accessory gland and the main gland in the same facial half. Aging changes, such as decreased glandular elements, increased fat, and increased fibrous connective tissue, were not more extensive in the accessory gland than in the main gland. Because of the histologic similarity, pathoses of the main gland could also involve the accessory parotid gland. Failure to remove a distantly separated accessory gland during parotidectomy could be a causeof tumor recurrence. X-ray films and sialograms were examined for visualization of accessory parotid glands and their ducts. Whereas routine diagnostic x-ray films were limited in their usefulness, sialograms provided visualization of accessory glands for diagnostic purposes. John ance
I wish to thank Dr. Barbara L. Carter for L. Giunta for assistance in histopathologic with the illustrations.
providing access to radiographic material, Dr. evaluations, and Mr. Daniel Casper for assist-
REFERENCES
of the Parotid Gland, St. Louis, 1965, The C. V. 1. Anderson, R., and Byars, L. T.: Surgery Mosby Company, pp. iv (preface), 3-6, 120-121. 2. McWhorter, G. L.: The Relations of the Superficial and Deep Lobes of the Parotid Gland to the Ducts and to the Facial Nerve, Anat. Rec. 12: 149-154, 1917. 3. McCormack, L. J., Cauldwell, E. W., and Anson, B. J.: The Surgical Anatomy of the Facial Nerve, Surg. Gynecol. Obstet. 80: 620-630, 1945. 4. McKenzie, J.: The Parotid Gland in Relation to the Facial Nerve, J. Anat. 82: 183-186 1948. 5. Davis, R. A., Anson, B. J., Budinger, J. M., and Kurth, L. E.: Surgical Anatomy of the Facial Nerve and Parotid Gland Based on a Study of 350 Cervicofacial Halves, Surg. Gynecol. Obstet. 102: 385412, 1956. F. Winsten, J., and Ward, G. E.: The Parotid Gland: An Anatomic Study, Surgery 40: 585 606, 1956. 7. Patey, D. H., and Ranger, I.: Some Points in the Surgical Anatomy of the Parotid Gland, Br. J. Surg. 45: 250-258, 1957. 8. Gasser, R. F.: The Early Development of the Parotid Gland Around the Facial Nerve and Its Branches in Man, Anat. Rec. 167: 63-78, 1970. 9. Perzik, S. L., and White, I. L.: Surgical Management of Preauricular Tumors of the Accessory Parotid Apparatus, Am. J. Surg. 112: 498-503, 1966. 10. White, I. L.: Sialoangiography: X-ray Visualization of Major Salivary Glands, Laryngoseopc 82: 2032.2048, 1972. Reprint requests to: Dr. Jack Frommer Department of Anatomy Tufts University Schools 136 Harrison Ave. Boston, Mass. 02111
of Medicine
and Dental
Medicine
OF
Ph.D.,*
MEDICINE
AND
Boston, DENTAL
Mass. MEDICINE,
TUFTS
UNIVERSITY
Dissections of human parotid glands were undertaken to observe the incidence, size, location, and histologic characteristics of accessory parotid glands. These data were related to the premise that an unusual location and appearance of the accessory gland might preclude complete surgical removal of a parotid tumor. This, in turn, could be a factor in the high recurrence rate after apparently total excision of benign mixed tumors of the parotid gland.
0
perations on the parotid gland involve difficulties not often encountered elsewhere by the general surge0n.l Not the least of these surgical obstacles is the “sandwich-like” or “lattice-like” arrangement of parts of the facial nerve within the glandular mass.2-8 Another difficulty is that of visualizing and removing all extensions of the widely ramifying gland, particularly the deep, retromandibular portion projecting toward the lateral pharyngeal space.l Appreciation of these aspects of parotid anatomy is important not only for the prevention of nerve damage during partial or complete parotidectomies, but also for making reasonably certain that the parotid tumors are completely removed during the operation.6 In spite of this knowledge of the surgical anatomy of the parotid gland, surgeons are occasionally faced with tumor recurrence, especially after excision of benign mixed tumors, which make up the greatest percentage of parotid tumors. An additional morphologic feature, the accessory parotid gland, warrants further study in this context. The observation of accessory glands which were quite far removed from the main gland made it seem evident that this separation from a principal surgical site might preclude the complete removal of a tumor and thus might be a cause of tumor recurrence. Many textbooks and journal articles mention an accessory parotid gland and A portion of this paper was presented at the eighty-eighth Association of Anatomists, Los Angeles, Calif., March, 1975; “Professor, Department of Anatomy.
annual
session
of the American
671
672
Pronww~
Fig. 1. Three variations at the anterior rstcnsion. B, Attached anterior extension mass or “accessory parotid gland” (APG).
border of the parotid gland (PC). A, No anterior or “facial process” (FP). C, Detached glandular
describe it in variable ways, but only one major report considers the clinicopathologic aspects and surgical management of it.” These investigators recognized that a swelling in the soft part of the cheek may represent a tumor of the “accessory parotid apparatus.” In their description of a special surgical approach in twenty patients who were suspected of having preauricular tumors in this region, they found that eleven of the twenty did have some form of lesion of the acessory parotid “area.” Anderson and Byarsl stated that benign parotid tumors may be found anywhere in the gland, including “far out on the cheek in the accessory portion.” The purpose of the present investigation was to observe the incidence, size, location, and histologic features of accessory parotid glands, and to relate these data to possible involvement in the recurrence of parotid tumors. X-ray films and sialograms were studied to determine how well the accessory glands could bc visualized for diagnostic purposes. Histologic sections of the accessory parotid gland were compared with sections of the main gland to determine whether pathosis of the main gland could also involve the accessory gland by the same neoplastic process. If differences existed, it would not be so likely that the recurrence of a parotid tumor could be ascribed to the accessory gland. However, other pathoses of the accessory mass could occur independently of, and be unrelated to, the parotid gland proper. MATERIALS
AND
METHODS
Ninety-six dissections were studied on adult human cadavers of both sexes. The presence, size, location, and relationships of accessory parotid glands were noted. An essential criterion for identification of an accessory parotid gland was its complete detachment from the main body of the gland. An attached anterior extension of the main gland along the course of the parotid duct is a “facial process” and was not categorized as an accessory gland (Fig. 1). Eight accessory glands, each with a segment of the major parotid gland from
Volume Number
43 5
Fig. tionship
8. A selection of several to Stensen’s duct (SD).
Human
large
accessory
parotid
accessory
glands
(LUG).
parotid
Note
gland
673
the
rela-
close
the same facial half, were removed for histologic processing. After additional (postembalming) fixation for 1 week in 10 per cent neutral buffered formalin, paraffin sections were cut at 6 to 10 p and stained either with hematoxylin and eosin or with Mallory’s trichrome. X-ray films and sialograms from the teaching collection of the Department of Radiology at the Tufts-New England Medical Center Hospitals were examined for visualization of accessory parotid glands and their ducts. RESULTS
Twenty of the ninety-six dissections (21 per cent) revealed clearly detached accessory glands, of variable size, shape, and position. Most of them could bc described in familiar terms as ranging in size from a small flattened pea to a large lima bean. The flattened appearance was the result of their compression between the masseter muscle and the skin. The accessory gland was bound to the masseter muscle by an extension of the masseteric fascia. It was found in close relation to Stensen’s duct in the anterior course of the duct across the muscle, usually lying on or above the duct (Fig. 2). The accessory gland usually had one major tributary emptying into Stensen’s duct, but occasionally two or more were observed. The average distance of distinctly separated accessory glands from the anterior edge of the main gland was
Oral May,
surg. 1977
Fig. 3. Histologic section showing normal aging characteristics which appear in the accessory gland and the main glandular mass of the same facial half. Note the decreased glandular element?, the increased proportion of fat, and the increase in fibrous connective tissue. (Hematoxyhn and cosin stain. Original magnification, x100.)
6.0 mm. The farthest removed accessory gland rested on the buccal fat pad at the anterior border of the masseter muscle. Histologic comparisons of the accessory and main glands revealed no appreciable differences in either their acini or their duct systems. An increased proportion of fat, accompanied by a proportional decrease in glandular elements, was seen in many accessory and main glands (Fig. 3). This was considered to be a normal aging phenomenon, as was an increase in fibrous connective tissue. These aging changes were not more extensive in the accessory gland than in the main gland. Slight inflammatory changes, in the form of scattered lymphocytes and periductal lymphocytosis, were seen occasionally and were equally evident in both glandular masses Routine diagnostic x-ray films did not reveal accessory parotid glands. Sialograms, for the recording of which a contrast medium was used to fill the parotid duct and its tributaries, did successfully reveal the duct system of accessory parotid glands (Fig. 4). DISCUSSION In their anatomic study of the parotid gland, Winsten and Ward” noted that, “although the knowledge of the anatomy is not vital in itself, the possible influence it might have on the surgical approach to parotid neoplasms is considerable.” Since the early anatomic study by McWhorter,2 there has been an overwhelming number of investigations aimed at defining the complex relationship between the facial nerve and the parotid gland in order to reduce the hazards of operation in this region. Another line of extensive investigations studied the “parotid bed” in order to minimize the difficulty of visualizing and removing the entire gland, thus hopefully reducing the recurrence rate after tumor excision.‘, G For many years the possible clinical significance of a separate glandular mass, the accessory parotid gland, was overlooked. The major reasons for this were twofold: one was the preoccupation with the anatomy of the gland-nerve relation-
Volume Number
frzmau
43 5
Fig. 4. Sialoangiograms gland is clearly revealed. Accessory parotid gland.
in which Conventional PG, Parotid
accesson~ parotid
ghtd
675
the duct system of a widely separated accessory parotid radiograph on the left, a reversal on the right. apt, gland.
ship; the other was the differences of interpretation in identifying an accessory parotid gland. There is still not complete agreement among authors and investigators that an accessory parotid gland should be completely detached from the main body of the gland. It is not uncommon to find illustrations and descriptions in which an attached anterior portion, the “facial process,” is identified as an accessory parotid gland. A continuous facial process, not easily overlooked in a parotidectomy, was of no concern in the present study. Many accessory parotid glands are located close to the main gland and would not easily escape notice during an operation. However, the more widely removed ones could, indeed, be overlooked in the usual operative field and would require a more extensive preoperative diagnosis as well as a wider surgical field. It is difficult to distinguish accessory parotid glands or their ducts in routine diagnostic x-ray examinations. Sialograms, however, will usually reveal the duct system of an accessory gland, and thus enable a surgeon to plan a wider operative field for a parotidectomy when the major and accessory portions are involved.” Histologically, the accessory and the main parotid glands are similar. There were no appreciable differences in either the acini or the duct systems, which indicates a similar secretory activity of the accessory and main portions of the gland. The normal aging processes, including fatty infiltration and fibrotic changes with the accompanying loss of glandular tissue, occur equally in the accessory and main gland. Because of the similarity of microscopic structure, any pathoses involving the main gland could also involve the accessory gland. Thus, failure to remove a distantly separated accessory gland during parotidectomy could conceivably result in the appearance of a second tumor after removal of the primary one.
A thorough understanding of the anatomy of the parotid gland is nccessar~ for accurate interpretations of sialoangiogramsl” and for the development of new surgical approaches in the parotid area.” Improved techniques increase the probability of excision of distantly separated accessory parotid glands and thcrcby reduce the possibility of tumor recurrence after parotidectomy. SUMMARY
Observations on ninety-six dissections of human parotid glands have been presented, with the incidence, size, location, and histologic features of accessory parotid glands noted. Twenty-one per cent of the dissections revealed clearly detached accessory glands at variable distances from the main gland. There were no appreciable histopathologic differences between the accessory gland and the main gland in the same facial half. Aging changes, such as decreased glandular elements, increased fat, and increased fibrous connective tissue, were not more extensive in the accessory gland than in the main gland. Because of the histologic similarity, pathoses of the main gland could also involve the accessory parotid gland. Failure to remove a distantly separated accessory gland during parotidectomy could be a causeof tumor recurrence. X-ray films and sialograms were examined for visualization of accessory parotid glands and their ducts. Whereas routine diagnostic x-ray films were limited in their usefulness, sialograms provided visualization of accessory glands for diagnostic purposes. John ance
I wish to thank Dr. Barbara L. Carter for L. Giunta for assistance in histopathologic with the illustrations.
providing access to radiographic material, Dr. evaluations, and Mr. Daniel Casper for assist-
REFERENCES
of the Parotid Gland, St. Louis, 1965, The C. V. 1. Anderson, R., and Byars, L. T.: Surgery Mosby Company, pp. iv (preface), 3-6, 120-121. 2. McWhorter, G. L.: The Relations of the Superficial and Deep Lobes of the Parotid Gland to the Ducts and to the Facial Nerve, Anat. Rec. 12: 149-154, 1917. 3. McCormack, L. J., Cauldwell, E. W., and Anson, B. J.: The Surgical Anatomy of the Facial Nerve, Surg. Gynecol. Obstet. 80: 620-630, 1945. 4. McKenzie, J.: The Parotid Gland in Relation to the Facial Nerve, J. Anat. 82: 183-186 1948. 5. Davis, R. A., Anson, B. J., Budinger, J. M., and Kurth, L. E.: Surgical Anatomy of the Facial Nerve and Parotid Gland Based on a Study of 350 Cervicofacial Halves, Surg. Gynecol. Obstet. 102: 385412, 1956. F. Winsten, J., and Ward, G. E.: The Parotid Gland: An Anatomic Study, Surgery 40: 585 606, 1956. 7. Patey, D. H., and Ranger, I.: Some Points in the Surgical Anatomy of the Parotid Gland, Br. J. Surg. 45: 250-258, 1957. 8. Gasser, R. F.: The Early Development of the Parotid Gland Around the Facial Nerve and Its Branches in Man, Anat. Rec. 167: 63-78, 1970. 9. Perzik, S. L., and White, I. L.: Surgical Management of Preauricular Tumors of the Accessory Parotid Apparatus, Am. J. Surg. 112: 498-503, 1966. 10. White, I. L.: Sialoangiography: X-ray Visualization of Major Salivary Glands, Laryngoseopc 82: 2032.2048, 1972. Reprint requests to: Dr. Jack Frommer Department of Anatomy Tufts University Schools 136 Harrison Ave. Boston, Mass. 02111
of Medicine
and Dental
Medicine