Lipomatous Salivary Gland Tumors

Abstract

Lipomatous neoplasms of the salivary glands are rare. Their wide histologic spectrum has not been sufficiently studied. We collected 31 fat-containing salivary gland lesions excluding pleomorphic adenoma and myoepithelioma with lipometaplasia. There were 19 male and 12 female patients aged 7 to 89 years (mean, 53 y). Tumors originated in the parotid (n=29) and the submandibular (n=2) gland. On the basis of the proportion and distribution of adipose tissue and the epithelial type, tumors could be categorized into 3 main groups: ordinary lipoma (n=20) identical to soft tissue lipoma but located within the salivary gland, oncocytic lipoadenoma (n=6) composed predominantly of oncocytes with variable fatty component, nononcocytic sialolipoma (n=4) composed of lobular fatty tissue (≥70%) with evenly distributed normal salivary tissue recapitulating the composition of normal salivary glands and microcystic lipoadenoma (n=1) composed of cystic ducts admixed with adipose tissue. The mean tumor size was 3.3, 3.8, and 2.9 cm for lipoma, oncocytic lipoadenoma, and nononcocytic sialolipoma, respectively. Associated diseases included Madelung disease with bilateral atypical lipomatous tumors of the neck and bilateral parotid lipoma (1), oncocytic lipoadenoma after irradiation for sinonasal adenocarcinoma (1), and periparotideal lipoma excised years before oncocytic lipoadenoma (1) and nononcocytic sialolipoma (1). No recurrence was recorded at a mean follow-up of 72 months (range, 6 to 184 mo). Sebaceous islands were seen in 5/6 oncocytic lipoadenomas and in 2/4 sialolipomas. Periductal inflammation/fibrosis was common in sialolipoma and oncocytic lipoadenoma. This study demonstrates the wide morphologic spectrum of fatty salivary gland lesions. Oncocytic lipoadenoma is an epithelial-predominant tumor that is distinct from the fat-dominated nononcocytic sialolipoma, but the 2 types seem to merge in some cases.

Oncocytic Lipoadenoma: A Rare Case of Parotid Gland Tumor and Review of the Literature

“…So-called dark cells were also common. Uncommon findings as sclerotic and polycystic changes ascribed to chronic involution, squamous metaplasia, lymphoid stroma, and metaplastic bone formation have been reported [ 1 , 2 ]. The presence of mitochondria in those oncocytic cells was confirmed by both immunohistochemical and ultrastructural studies [ 7 ].…”

Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumors of the Salivary Gland

“…Nodular fasciitis may rarely involve the superficial parotid gland. As with other sites, these tend to occur in young adults (3rd to 4th decade) and show a characteristic rapid growth mimicking an aggressive neoplasm [23]. Histologically similar to nodular fasciitis at other sites, parotid lesions consist of a well demarcated but focally permeative myofibroblastic proliferation that is cellular but with little atypia.…”

“…They are well circumscribed and are designated as sialolipoma if they have an intratumoral ductal component. Oncocytic lipoadenoma appears to be a distinctive subtype of sialolipoma with oncocytes and sebaceous rests [23]. Nodular fasciitis may rarely involve the superficial parotid gland.…”

“…The majority are now known to harbor an USP6 gene fusion [24]. Nodular fasciitis must be distinguished from more aggressive spindle cell sarcomas, as well as spindle cell myoepithelial cell rich neoplasms [23]. Other considerations in this region include schwannoma and solitary fibrous tumor.…”

Lipomatosis of the parotid salivary gland: 2 case reports and review of the literature on fat-containing salivary gland lesions

“…In human patients the salivary gland can also be enlarged due to fat-containing lesions. These are uncommon and include sialolipoma, salivary lipomatosis, lipoadenoma, angiolipoma and adenoma with lipometaplasia [9], [10], [11], [12]. In dogs there are few reported cases of fat-containing salivary gland lesions and most of these have been classified as either sialolipoma or salivary lipomatosis [7], [13].…”