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Sialolipoma of the parotid gland
ARTICLE IN PRESS Journal of Cranio-Maxillofacial Surgery (2006) 34, 43–46 r 2005 European Association for Cranio-Maxillofacial Surgery doi:10.1016/j.jcms.2005.08.008, available online at http://www.sciencedirect.com
Case Report Sialolipoma of the parotid gland Ioannis George-Akrivos MICHAELIDIS1, Panagiotis Konstantinos STEFANOPOULOS1, Demetrios SAMBAZIOTIS2, Marios Alexandros ZAHOS3, George Alexandros PAPADIMITRIOU1 1
Department of Oral and Maxillofacial Surgery (Director: I. Michaelidis, DDS); 2Department of Pathological Anatomy (Director: D. Sambaziotis, MD); 3Oral Radiology Section, Department of Oral and Maxillofacial Surgery, 401 Army Hospital, Athens, Greece
A case of slow-enlarging mass of the parotid region in a 44-year-old male is presented, which proved to be a lipomatous tumour of the parotid gland. The clinical impression was that of a benign salivary gland tumour. The tumour was situated in the deep lobe of the gland, thus a total parotidectomy was performed, with preservation of the facial nerve. Microscopically the lesion was described as consisting of mature adipose tissue, which, however, encompassed both glandular elements and nerve bundles within it. This tumour has been recently recognized as a separate entity under the term ‘sialolipoma’. r 2005 European Association for Cranio-Maxillofacial Surgery
SUMMARY.
with the CT scan led to the tentative diagnosis of lipoma. Under general anaesthesia, a total parotidectomy was performed via a preauricular incision, with preservation of the facial nerve. The latter, however, was proved to be laborious, because of close proximity of the nerve to the tumour. The resultant contour deformity below the earlobe was corrected with the use of the superficial portion of the sternocleidomastoid muscle rotated around its insertion onto the mastoid process according to Rauch (1965). The tumour had a fatty consistency and measured 3.5 cm at its largest diameter. Microscopically it consisted of mature adipose tissue surrounded by a thin fibrous capsule with incomplete septae extending into the tumour mass (Fig. 3). Within the lesion there were islands of glandular tissue consisting of acinar elements with few ductal structures (Fig. 4) and nerve bundles (Fig. 5). In conclusion, the lesion was characterized as parotid lipoma enclosing glandular elements and, on the basis of a recent report by Nagao et al. (2001), it was further defined as sialolipoma. Peripherally the parotid parenchyma exhibited fatty degeneration of a moderate degree. Postoperatively there was facial nerve weakness due to surgical manipulations, as anticipated, but return to normal function occurred within 1 month. The patient was followed-up for 2 years without any sign of recurrence.
INTRODUCTION Lipoma is the most common soft-tissue tumour of adulthood and occurs frequently in the head and neck area (Kyriakos and El-Mofty, 1999). However, lipomas of the salivary glands are quite rare with the highest frequency reported in the parotid gland, which has a significant fat content as a normal feature (Cawson et al., 1997). Until recently lipomatous tumours containing salivary gland elements were not regarded as a distinct entity. However, there is a growing body of evidence suggesting that these tumours should be separated from ordinary lipomas on the basis of their morphologic characteristics and possibly clinical behaviour (Nagao et al., 2001; Fregnani et al., 2003). A rare case of lipomatous lesion of the parotid gland is presented encompassing glandular and neural elements.
CASE REPORT A previously healthy, 44-year-old male was seen for evaluation of a swelling in the right preauricular area of one and a half year’s duration (Fig. 1). The ‘lump’ was painless and movable with a soft consistency and extended to the lower pole of the parotid gland. It did not appear to involve any of the adjacent anatomical structures and mouth opening was normal. The function of the facial nerve was intact. The CT scan revealed a deep lobe lesion of low density (Fig. 2). A fine-needle aspiration biopsy taken from the mass showed few mature adipocytes and was negative for malignancy. Although the fineneedle aspiration biopsy could not exclude lipomatosis of the parotid gland, these findings in conjuction
DISCUSSION Lipomas represent 20% of all benign mesenchymal tumours of the salivary glands (Seifert et al., 1999). 43
ARTICLE IN PRESS 44 Journal of Cranio-Maxillofacial Surgery
Fig. 3 – Photomicrograph of peripheral part of tumour: fibrous capsule separating tumour from adjacent glandular parenchyma (which exhibits fatty degeneration; H&E 250).
Fig. 1 – 44-year-old male patient with a lump in the right parotid region.
Fig. 4 – Central part of tumour: normal glandular tissue within tumour mass (H&E 250).
Fig. 2 – CT scan of upper neck: low density mass in the deep lobe of the right parotid gland consistent with a lipomatous tumour.
In the parotid gland where they are most common they account for about 1% of all parotid tumours (Baker et al., 1981), with a male predominance and an
Fig. 5 – Presence of nerve bundles completely encircled by neoplastic elements (H&E 250).
age peak in the 5th and 6th decade (Seifert et al., 1999). Approximately 90% of these cases are ordinary lipomas with the remaining lesions being
ARTICLE IN PRESS Sialolipoma of the parotid gland 45
either infiltrating lipomas, or occurring as part of a lipomatosis syndrome (Rabinov, 2000). However, it seems that distinction between these conditions is not solely of academic interest. True lipomas of the parotid gland are encapsulated tumours of soft consistency, characterized by mature adipocytes in a lobular arrangement which replace the normal gland parenchyma (Seifert et al., 1999). Benign lipomatous tumours of the salivary glands with entrapped glandular components have recently been recognized as a separate entity by Nagao et al. (2001) who proposed the term sialolipoma for these lesions. The main histological features of these tumours consist of: (1) mature adipose tissue surrounded by a very thin fibrous capsule and (2) islands of acinous elements with few ductal structures contained within the lipomatous mass. The intermingling salivary gland tissue is most likely not part of the neoplastic process but, as Nagao et al. (2001) have pointed out, this possibility cannot be excluded with certainty; nevertheless, newer molecular techniques may be helpful in elucidating the histogenesis of this tumour (Nagao et al., 2001). In the present case, an additional microscopic feature, previously described in one of the cases of Nagao et al. (2001), was the presence of small nerve branches encircled by the tumour. This finding reflects the difficulties encountered intraoperatively in freeing the involved portion of the gland from the facial nerve, perhaps indicating a more aggressive mode of growth of this lesion than that attributed to ordinary lipomas. Alternatively, a multicentric proliferation of adipose tissue, ultimately entrapping interstitial normal structures, can be assumed, in view of the fatty degeneration of the gland demonstrated by both the fine-needle aspiration and the final biopsies. However, it should be noted that the medical history of the patient did not reveal any of the conditions associated with lipomatosis, namely diabetes mellitus, chronic alcoholism or liver cirrhosis. Furthermore, the presence of a fibrous capsule readily distinguishes a lipoma from lipomatosis of the salivary gland (Cawson et al., 1997; Nagao et al., 2001) and such a capsule was prominent albeit thin in the case reported here, thus making the possibility of neoplastic transformation of preexisting lipomatosis less convincing. With regard to the preoperative assessment, many authors favour fine-needle aspiration biopsy as a primary diagnostic mode, and this was found most helpful in the present case. Furthermore, lipomatosis tumours are among the few salivary tumours in which a specific tissue diagnosis can be made using the CT; they typically have low attenuation reflecting their high fat content (DelBalso, 1995; Rabinov, 2000). Therefore, the combination of fine-needle aspiration and CT findings should promptly orientate the clinician towards a lipomatous tumour of the parotid gland. However, it should be kept in mind that both cannot distinguish between benign and malignant lesions with certainty.
Besides lipomatosis, the differential diagnosis of a lipomatous tumour of the parotid gland should include lipomatous pleomorphic adenoma and lipoadenoma. In the first case, adenomatous tissue shows the typical features of pleomorphic adenoma, including ducts and sheets or strands of (dark-staining) epithelial cells, intermingled with fibrous and myxoid elements, and compressed between mature adipose tissue, which constitutes more than 90% of the tumour mass (Seifert et al., 1999). Lipoadenoma, on the other hand, is composed of an intimate admixture of adipose tissue and ducts containing eosinophilic proteinaceous material (Seifert et al., 1999), which may show cystic dilation but, in contrast to sialolipoma, are deprived of acinar cells (Hirokawa et al., 2002). Regarding the proliferative activity of sialolipoma, Fregnani et al. (2003) found increased proliferating cell nuclear antigen expression in comparison with common lipomas. Although this index might suggest faster growth of the lesion, this did not appear to be an important prognostic factor since there was no recurrence after surgical treatment (Fregnani et al., 2003) and this was also the impression from the present case. Nevertheless, in view of the unique characteristics of this rare tumour, more clinical studies are required before safe conclusions are made about its behaviour.
CONCLUSIONS In parotid surgery it should be remembered that a preoperative CT image of a lipomatous lesion may in fact mask a more invasive tumour, such as the newly recognized sialolipoma. This tumour has recently undergone revision in terms of its microscopic features, which justify separation from ordinary lipomas. This is the first report of sialadenolipoma described from both a pathologist and surgeon’s viewpoint, illustrating the technical difficulties during its excision, mainly with respect to preservation of the facial nerve, which were consistent with its locally invasive microscopic characteristics. Based on the present experience the surgeon confronted with such a tumour should be prepared to perform a more extensive parotidectomy procedure than is usually required for lesions of lipomatous origin. References Baker SE, Jensen JL, Correll RW: Lipomas of the parotid gland. Oral Surg Oral Med Oral Pathol 52: 167–171, 1981 Cawson RA, Gleeson MJ, Eveson JW: Mesenchymal, lymphoreticular, metastatic and periglandular tumours and other uncommon types of salivary gland tumours. In: Cawson RA, Gleeson MJ, Eveson JW (Eds.), Pathology and Surgery of the Salivary Glands. Isis Medical Media, Oxford, p. 175, 1997 DelBalso A: Salivary imaging. Oral Maxillofac Surg Clin North Am 7: 387–422, 1995 Fregnani ER, Pires FR, Falzoni R, Lopes MA, Vargas PA: Lipomas of the oral cavity: clinical findings, histological
ARTICLE IN PRESS 46 Journal of Cranio-Maxillofacial Surgery classification and proliferative activity of 46 cases. Int J Oral Maxillofac Surg 32: 49–53, 2003 Hirokawa M, Bando Y, Tashiro T, Kuma S, Kawata I, Sano T: Parotid lipoadenoma with sclerotic and polycystic changes. Virchows Arch 440: 549–550, 2002 Kyriakos M, El-Mofty S: Pathology of selected soft-tissue tumors of the head and neck. In: Thawley SE, Panje WR, Batsakis JG, Lindberg RD (Eds.), Comprehensive Management of Head and Neck Tumors, 2nd edition. W.B. Saunders, Philadelphia, pp. 1322–1394, 1999 Nagao T, Sugano I, Ishida Y, Asoh A, Munakata S, Yamazaki K, Konno A, Kondo Y, Nagao K: Sialolipoma: a report of seven cases of a new variant of salivary gland lipoma. Histopathology 38: 30–36, 2001 Rabinov JD: Imaging of salivary gland pathology. Radiol Clin North Am 38: 1047–1057, 2000 Rauch S: Muskula¨re Substitutionsplastik nach Parotidektomie. HNO 13: 20–22, 1965
Seifert G, Donath K, Scha¨fer R: Lipomatous pleomorphic adenoma of the parotid gland: classification of lipomatous tissue in salivary glands. Pathol Res Pract 195: 247–252, 1999
Ioannis MICHAELIDIS 34-36 A. Tritsi Street Patima Halandri 15238 Athens Greece Tel.: (+) 30 210 7494215 E-mail: [email protected] Paper received 20 February 2004 Accepted 10 August 2005
Case Report Sialolipoma of the parotid gland Ioannis George-Akrivos MICHAELIDIS1, Panagiotis Konstantinos STEFANOPOULOS1, Demetrios SAMBAZIOTIS2, Marios Alexandros ZAHOS3, George Alexandros PAPADIMITRIOU1 1
Department of Oral and Maxillofacial Surgery (Director: I. Michaelidis, DDS); 2Department of Pathological Anatomy (Director: D. Sambaziotis, MD); 3Oral Radiology Section, Department of Oral and Maxillofacial Surgery, 401 Army Hospital, Athens, Greece
A case of slow-enlarging mass of the parotid region in a 44-year-old male is presented, which proved to be a lipomatous tumour of the parotid gland. The clinical impression was that of a benign salivary gland tumour. The tumour was situated in the deep lobe of the gland, thus a total parotidectomy was performed, with preservation of the facial nerve. Microscopically the lesion was described as consisting of mature adipose tissue, which, however, encompassed both glandular elements and nerve bundles within it. This tumour has been recently recognized as a separate entity under the term ‘sialolipoma’. r 2005 European Association for Cranio-Maxillofacial Surgery
SUMMARY.
with the CT scan led to the tentative diagnosis of lipoma. Under general anaesthesia, a total parotidectomy was performed via a preauricular incision, with preservation of the facial nerve. The latter, however, was proved to be laborious, because of close proximity of the nerve to the tumour. The resultant contour deformity below the earlobe was corrected with the use of the superficial portion of the sternocleidomastoid muscle rotated around its insertion onto the mastoid process according to Rauch (1965). The tumour had a fatty consistency and measured 3.5 cm at its largest diameter. Microscopically it consisted of mature adipose tissue surrounded by a thin fibrous capsule with incomplete septae extending into the tumour mass (Fig. 3). Within the lesion there were islands of glandular tissue consisting of acinar elements with few ductal structures (Fig. 4) and nerve bundles (Fig. 5). In conclusion, the lesion was characterized as parotid lipoma enclosing glandular elements and, on the basis of a recent report by Nagao et al. (2001), it was further defined as sialolipoma. Peripherally the parotid parenchyma exhibited fatty degeneration of a moderate degree. Postoperatively there was facial nerve weakness due to surgical manipulations, as anticipated, but return to normal function occurred within 1 month. The patient was followed-up for 2 years without any sign of recurrence.
INTRODUCTION Lipoma is the most common soft-tissue tumour of adulthood and occurs frequently in the head and neck area (Kyriakos and El-Mofty, 1999). However, lipomas of the salivary glands are quite rare with the highest frequency reported in the parotid gland, which has a significant fat content as a normal feature (Cawson et al., 1997). Until recently lipomatous tumours containing salivary gland elements were not regarded as a distinct entity. However, there is a growing body of evidence suggesting that these tumours should be separated from ordinary lipomas on the basis of their morphologic characteristics and possibly clinical behaviour (Nagao et al., 2001; Fregnani et al., 2003). A rare case of lipomatous lesion of the parotid gland is presented encompassing glandular and neural elements.
CASE REPORT A previously healthy, 44-year-old male was seen for evaluation of a swelling in the right preauricular area of one and a half year’s duration (Fig. 1). The ‘lump’ was painless and movable with a soft consistency and extended to the lower pole of the parotid gland. It did not appear to involve any of the adjacent anatomical structures and mouth opening was normal. The function of the facial nerve was intact. The CT scan revealed a deep lobe lesion of low density (Fig. 2). A fine-needle aspiration biopsy taken from the mass showed few mature adipocytes and was negative for malignancy. Although the fineneedle aspiration biopsy could not exclude lipomatosis of the parotid gland, these findings in conjuction
DISCUSSION Lipomas represent 20% of all benign mesenchymal tumours of the salivary glands (Seifert et al., 1999). 43
ARTICLE IN PRESS 44 Journal of Cranio-Maxillofacial Surgery
Fig. 3 – Photomicrograph of peripheral part of tumour: fibrous capsule separating tumour from adjacent glandular parenchyma (which exhibits fatty degeneration; H&E 250).
Fig. 1 – 44-year-old male patient with a lump in the right parotid region.
Fig. 4 – Central part of tumour: normal glandular tissue within tumour mass (H&E 250).
Fig. 2 – CT scan of upper neck: low density mass in the deep lobe of the right parotid gland consistent with a lipomatous tumour.
In the parotid gland where they are most common they account for about 1% of all parotid tumours (Baker et al., 1981), with a male predominance and an
Fig. 5 – Presence of nerve bundles completely encircled by neoplastic elements (H&E 250).
age peak in the 5th and 6th decade (Seifert et al., 1999). Approximately 90% of these cases are ordinary lipomas with the remaining lesions being
ARTICLE IN PRESS Sialolipoma of the parotid gland 45
either infiltrating lipomas, or occurring as part of a lipomatosis syndrome (Rabinov, 2000). However, it seems that distinction between these conditions is not solely of academic interest. True lipomas of the parotid gland are encapsulated tumours of soft consistency, characterized by mature adipocytes in a lobular arrangement which replace the normal gland parenchyma (Seifert et al., 1999). Benign lipomatous tumours of the salivary glands with entrapped glandular components have recently been recognized as a separate entity by Nagao et al. (2001) who proposed the term sialolipoma for these lesions. The main histological features of these tumours consist of: (1) mature adipose tissue surrounded by a very thin fibrous capsule and (2) islands of acinous elements with few ductal structures contained within the lipomatous mass. The intermingling salivary gland tissue is most likely not part of the neoplastic process but, as Nagao et al. (2001) have pointed out, this possibility cannot be excluded with certainty; nevertheless, newer molecular techniques may be helpful in elucidating the histogenesis of this tumour (Nagao et al., 2001). In the present case, an additional microscopic feature, previously described in one of the cases of Nagao et al. (2001), was the presence of small nerve branches encircled by the tumour. This finding reflects the difficulties encountered intraoperatively in freeing the involved portion of the gland from the facial nerve, perhaps indicating a more aggressive mode of growth of this lesion than that attributed to ordinary lipomas. Alternatively, a multicentric proliferation of adipose tissue, ultimately entrapping interstitial normal structures, can be assumed, in view of the fatty degeneration of the gland demonstrated by both the fine-needle aspiration and the final biopsies. However, it should be noted that the medical history of the patient did not reveal any of the conditions associated with lipomatosis, namely diabetes mellitus, chronic alcoholism or liver cirrhosis. Furthermore, the presence of a fibrous capsule readily distinguishes a lipoma from lipomatosis of the salivary gland (Cawson et al., 1997; Nagao et al., 2001) and such a capsule was prominent albeit thin in the case reported here, thus making the possibility of neoplastic transformation of preexisting lipomatosis less convincing. With regard to the preoperative assessment, many authors favour fine-needle aspiration biopsy as a primary diagnostic mode, and this was found most helpful in the present case. Furthermore, lipomatosis tumours are among the few salivary tumours in which a specific tissue diagnosis can be made using the CT; they typically have low attenuation reflecting their high fat content (DelBalso, 1995; Rabinov, 2000). Therefore, the combination of fine-needle aspiration and CT findings should promptly orientate the clinician towards a lipomatous tumour of the parotid gland. However, it should be kept in mind that both cannot distinguish between benign and malignant lesions with certainty.
Besides lipomatosis, the differential diagnosis of a lipomatous tumour of the parotid gland should include lipomatous pleomorphic adenoma and lipoadenoma. In the first case, adenomatous tissue shows the typical features of pleomorphic adenoma, including ducts and sheets or strands of (dark-staining) epithelial cells, intermingled with fibrous and myxoid elements, and compressed between mature adipose tissue, which constitutes more than 90% of the tumour mass (Seifert et al., 1999). Lipoadenoma, on the other hand, is composed of an intimate admixture of adipose tissue and ducts containing eosinophilic proteinaceous material (Seifert et al., 1999), which may show cystic dilation but, in contrast to sialolipoma, are deprived of acinar cells (Hirokawa et al., 2002). Regarding the proliferative activity of sialolipoma, Fregnani et al. (2003) found increased proliferating cell nuclear antigen expression in comparison with common lipomas. Although this index might suggest faster growth of the lesion, this did not appear to be an important prognostic factor since there was no recurrence after surgical treatment (Fregnani et al., 2003) and this was also the impression from the present case. Nevertheless, in view of the unique characteristics of this rare tumour, more clinical studies are required before safe conclusions are made about its behaviour.
CONCLUSIONS In parotid surgery it should be remembered that a preoperative CT image of a lipomatous lesion may in fact mask a more invasive tumour, such as the newly recognized sialolipoma. This tumour has recently undergone revision in terms of its microscopic features, which justify separation from ordinary lipomas. This is the first report of sialadenolipoma described from both a pathologist and surgeon’s viewpoint, illustrating the technical difficulties during its excision, mainly with respect to preservation of the facial nerve, which were consistent with its locally invasive microscopic characteristics. Based on the present experience the surgeon confronted with such a tumour should be prepared to perform a more extensive parotidectomy procedure than is usually required for lesions of lipomatous origin. References Baker SE, Jensen JL, Correll RW: Lipomas of the parotid gland. Oral Surg Oral Med Oral Pathol 52: 167–171, 1981 Cawson RA, Gleeson MJ, Eveson JW: Mesenchymal, lymphoreticular, metastatic and periglandular tumours and other uncommon types of salivary gland tumours. In: Cawson RA, Gleeson MJ, Eveson JW (Eds.), Pathology and Surgery of the Salivary Glands. Isis Medical Media, Oxford, p. 175, 1997 DelBalso A: Salivary imaging. Oral Maxillofac Surg Clin North Am 7: 387–422, 1995 Fregnani ER, Pires FR, Falzoni R, Lopes MA, Vargas PA: Lipomas of the oral cavity: clinical findings, histological
ARTICLE IN PRESS 46 Journal of Cranio-Maxillofacial Surgery classification and proliferative activity of 46 cases. Int J Oral Maxillofac Surg 32: 49–53, 2003 Hirokawa M, Bando Y, Tashiro T, Kuma S, Kawata I, Sano T: Parotid lipoadenoma with sclerotic and polycystic changes. Virchows Arch 440: 549–550, 2002 Kyriakos M, El-Mofty S: Pathology of selected soft-tissue tumors of the head and neck. In: Thawley SE, Panje WR, Batsakis JG, Lindberg RD (Eds.), Comprehensive Management of Head and Neck Tumors, 2nd edition. W.B. Saunders, Philadelphia, pp. 1322–1394, 1999 Nagao T, Sugano I, Ishida Y, Asoh A, Munakata S, Yamazaki K, Konno A, Kondo Y, Nagao K: Sialolipoma: a report of seven cases of a new variant of salivary gland lipoma. Histopathology 38: 30–36, 2001 Rabinov JD: Imaging of salivary gland pathology. Radiol Clin North Am 38: 1047–1057, 2000 Rauch S: Muskula¨re Substitutionsplastik nach Parotidektomie. HNO 13: 20–22, 1965
Seifert G, Donath K, Scha¨fer R: Lipomatous pleomorphic adenoma of the parotid gland: classification of lipomatous tissue in salivary glands. Pathol Res Pract 195: 247–252, 1999
Ioannis MICHAELIDIS 34-36 A. Tritsi Street Patima Halandri 15238 Athens Greece Tel.: (+) 30 210 7494215 E-mail: [email protected] Paper received 20 February 2004 Accepted 10 August 2005