Adenolipoma of the thyroid gland

Sialolipoma: Report of two cases and review of the literature

Sialolipoma is a new variant of salivary gland lipoma first described in 2001. We present 2 cases of sialolipoma involving the soft palate and buccal mucosa of 2 female patients. A review of the English language literature revealed 16 cases of sialolipoma reported thus far. We have reviewed the clinicopathologic features of the literature cases and are adding the present 2 cases for a total of 18 cases. To the best of our knowledge, this is the first report of sialolipoma involving the buccal mucosa and the second case in the soft palate. The purpose of this publication is to increase awareness of this recently described variant of lipoma and to address the diagnostic challenges posed both clinically and histopathologically.

Sialolipoma: a report of seven cases of a new variant of salivary gland lipoma

AIMS

We propose the designation 'sialolipoma' to establish and characterize a new category of benign lipomatous tumour occurring in salivary glands. Until now, these tumours have not been regarded as a distinct entity in the salivary glands.

METHODS AND RESULTS

We evaluated the clinicopathological and immunohistochemical features of seven sialolipomas among 2051 surgically resected primary salivary gland tumours deposited in our files. The seven patients with sialolipoma were five men and two women, aged 20-75 years (mean: 54.4 years). Five tumours had arisen in the parotid gland, one in the soft palate, and one in the hard palate. The tumours ranged from 10 to 60 mm (mean: 38 mm) in maximum diameter. Histologically, the tumours were characterized by a well circumscribed mass composed of glandular tissue and mature adipose elements. The adipose elements in the tumours arising in the parotid gland were more abundant than those arising in the minor salivary gland. The glandular components consisted of ductal, acinar, basal and myoepithelial cells, and closely resembled the cellular and structural compositions of normal salivary gland tissues. These findings were confirmed by immunohistochemical and ultrastructural studies. These components had no atypia, except for the presence of some minor variations, e.g. ductal ectasia with fibrosis and focal oncocytic metaplasia. In all cases, cell proliferative activity, as assessed by Ki67 (MIB1) immunostaining, was low. From these findings, it is likely that our cases were lipomas with secondary entrapment of the salivary gland elements. No recurrence was seen in all cases after superficial parotidectomy, or after surgical excision in the patients with palatal tumours.

CONCLUSIONS

We regard sialolipoma as a distinct variant of salivary gland lipoma that can occur in both the major and minor salivary glands. Superficial parotidectomy, or surgical resection in the case of palatal tumours, is an appropriate treatment for this benign tumour.

Lipomatous pleomorphic adenoma of the parotid gland. Classification of lipomatous tissue in salivary glands

Lipomatous pleomorphic adenoma is an unusual subtype with a lipomatous stromal component of more than 90% of the tumour tissue. This special type of pleomorphic adenoma must be distinguished from other types of lipomatous tumours or non-tumourous lipomatosis of the salivary glands. Until now only two cases of lipomatous pleomorphic adenoma have been reported in the literature. We report of a 36-year old woman who developed a well circumscribed nodule measuring 3.5 x 2.5 x 2 cm in the right parotid gland. The cut surface was grey-yellowish. Histologically, more than 90% of the tumour tissue was fatty tissue with univacuolar adipocytes. The pleomorphic epithelial elements were duct-like cells forming small lumina and spindle-shaped myoepithelial cell with surrounding mucoid stroma. Components of pleomorphic adenoma were intermingled with mature adipose tissue which was more concentrated in the central portion of the adenoma. Some compressed epithelial cords in the adipose tissue formed a septa-like pattern. The differential diagnosis to other lipomatous tumours (lipoadenoma, lipoma) and to non-tumourous interstitial lipomatosis as well as the possible pathogenesis as metaplastic change or epithelial-mesenchymal transdifferentiation are discussed.

Oncocytic lipoadenoma of the submandibular gland

We report a case of oncocytic lipoadenoma of the submandibular gland, previously unrecognized benign tumor of the salivary gland. The patient was a 66-year-old Japanese woman with a left submandibular mass, measuring 11 x 7.5 x 5 cm. Microscopically, the mass was completely surrounded by a thin fibrous connective tissue capsule, and was composed of an intimate admixture of mature fat cells and oncocytes. There have been no English reports of such a neoplasm in the salivary gland with the exception of one recent case report of lipoadenoma of the parotid gland without oncocytic features. We propose the diagnostic term "oncocytic lipoadenoma" for this benign tumor.