Fat-containing salivary gland tumors: a review

Abstract

Fat-containing tumors of the salivary glands are uncommon. Their wide histological spectrum varies from pure lipomatous neoplasms similar to their cutaneous and soft tissue counterparts to mixed lipoepithelial lesions specific to the salivary glands. With few exceptions, these uncommon lesions affect mainly the elderly, with a mean age at presentation of ≥ 50 years and show a predilection for males. A few cases occur in childhood; some of them represent congenital lesions. In decreasing order of frequency, ordinary (soft-tissue type) lipoma, oncocytic lipoadenoma, non-oncocytic sialolipoma, and pleomorphic adenoma/myoepithelioma with extensive lipometaplasia are the main variants of fat containing tumors encountered in the salivary glands. While pleomorphic adenoma/myoepithelioma with lipometaplasia behave in the same way as their non-fat-containing counterparts, other lipomatous salivary gland tumors listed above are cured with simple excision and do not carry a risk of recurrence. Other lipoma variants (spindle cell lipoma, osteolipoma, fibrolipoma, angiolipoma, pleomorphic lipoma, lipoblastoma and hibernoma) are exceptionally rare in the salivary gland. Atypical lipomatous tumors/liposarcoma have been only rarely reported in the salivary gland and they behave in a similar fashion to their soft-tissue counterparts. Diffuse lipomatosis and lobular fatty atrophy are the two tumor-like lesions that might closely mimic sialolipoma, particularly in limited biopsy material without knowledge of the gross findings. This review summarizes the clinicopathological features of the main types of salivary fat-containing lesions and discusses their differential diagnoses.

Fig. 1

Parotid gland myoepithelioma with extensive lipometaplasia closely mimicking a mesenchymal lipomatous neoplasm

Fig. 2

a Sialolipoma showed lobules with a predominance of fat entrapping normal looking salivary elements. b Sebaceous metaplasia involving a duct with periductal lymphoid reaction. Note normal salivary tissue within the lesion on the right

Fig. 3

Oncocytic lipoadenoma featured compact oncocytes resembling oncocytic adenoma with adjacent serous acini and fat cells

Fig. 4

This encapsulated nodule showed equal amount of adipocytes and cystic ducts within fibrous stroma. Microcystic lipoadenoma was suggested as a descriptive term for this unclassified rare lesion

Fig. 5

a whole mount section of ordinary lipoma of parotid gland showed complete intraglandular location and encapsulation. b bland adipocytes are seen at higher magnification