Although lipoma is a common soft tissue tumor, it rarely occurs in the salivary gland [12
]. Lipomatous lesions, such sialolipoma, lipoadenoma, lipometaplasia in pleomorphic adenoma and lipomatosis, have attracted interest in recent years [2
]. Oral lipomas developing in association with salivary glandular elements have been recognized in surgical specimens and have been designated as sialolipoma [3
]. The sialolipoma is believed to be a lipoma with secondary normal salivary gland elements. It was considered as a distinct variant of salivary gland lipoma that can occur in both major and minor salivary glands. There have been few literature reports for this kind of tumor [3
Upon microscopic examination, sialolipomas are characterized by a well-circumscribed, often encapsulated mass, composed of benign, neoplastic, adipose tissue with scattered foci of generally atrophic, nonneoplastic, salivary gland acini and ducts contained within the lipomatous proliferation. Adipose tissue constitutes 90% of parotid gland sialolipomas and 50% of palate cases [9
]. We noted a well-delineated tumor consisting of a proliferation of adipose tissue and entrapped normal salivary gland elements with equal tissue distribution.
The entrapped epithelial islets consist of normal duct-acinar units of the salivary gland parenchyma [9
]. In this case, the epithelial components were clustered and the glandular components showed acinar atrophy. Yet, the ductal structures exhibited dilatation, hyperplasia and thin fibrous tissue around them. Some authors have reported an intense lymphoid infiltrate, marked ductal dilatation, fibrosis and myxoid change in adipose tissue [1
]. We observed scarce chronic inflammatory cells and no myxoid areas.
The microscopic differential diagnosis of sialolipoma includes lesions with extensive adipose tissue, such as lipomatosis and pleomorphic adenoma with extensive adipose content [3
]. Lipomatosis is nonmalignant overgrowth of adipose tissue throughout the salivary gland parenchyma, resulting in an intensive shrinkage of acinar cells, while sialolipoma is well-capsulate and exhibits ductal dilatation [9
]. Pleomorphic adenoma has distinct histological features to sialolipoma, including ducts and sheets or strands of dark-staining epithelial cells [13
The treatment of the sialolipoma consists of conservative surgical excision, and neither local recurrence nor malignant transformation has been reported [1
]. In the present case no evidence of recurrence has been noted 8 months after surgical excision.