Lipomatous mixed tumour of the skin: a histological, immunohistochemical and ultrastructural study

Abstract

The tumour differed from lipomas with myxoid stroma and from lipoadenomas, which show non-proliferating normal sweat glands admixed with adipose tissue. Because of the similarity to lipomatous pleomorphic adenoma/mixed tumour of salivary glands, we suggest that it should be called 'lipomatous mixed tumour of the skin'.

Pleomorphic Adenoma With Extensive Lipometaplasia

“…These cases confirm the existence of the previously described entity, pleomorphic adenoma with extensive lipometaplasia, and further confirm its occurrence within minor salivary glands. 7 A similar dermatologic lesion, lipomatous mixed tumor of the skin, has been described, 17 and lesser degrees of lipocytic differentiation have been described in mixed tumors and myoepitheliomas of soft tissue. 11 Another salivary gland tumor that is associated with adipose tissue is the lipoadenoma or sialolipoma.…”

Apocrine mixed tumor of the skin (“mixed tumor of the folliculosebaceous-apocrine complex”)

“…14,94-97 Uncommon cases of lipomatous pleomorphic adenoma of salivary glands and ceruminous glands have also been reported. 10,89,90,98 Ultrastructural studies have suggested that adipose tissue results from lipomatous metaplasia of myoepithelial cells, as individual transitional cells containing lipid droplets, 89 tonofilaments, 90 and myofilaments 14 have been identified. It has been claimed that the presence of adipose differentiation in AMT may be mutually exclusive with chondroid differentiation, 95 but 25 cases in our series exhibited simultaneously the presence of lipomatous and chondroid metaplasia.…”

“…12 Sometimes these changes are so prominent as to cause misdiagnosis with other adnexal or mesenchymal neoplasms. [13][14][15] However, a systematic analysis of the entire spectrum of various forms of differentiation and metaplastic epiphenomena in cutaneous AMTs has never been performed, as far as we are aware. Few previously published small series mainly focused on the spectrum of apocrinefolliculosebaceous differentiation.…”

Lipomatous Mixed Tumor of the Skin

“…4 The scattered case reports demonstrated that phenomenon in the pleomorphic adenomas of the salivary glands. 12-15 Lipomatous 6,8,12,16 or entrapment of the adipose tissue by the growing tumor. 13,14 Metaplastic change of the myoepithelial cells into the adipocytes was suggested not only due to morphological observations of transition between these 2 types of cells and the presence of intermediate cells but also due to ultrastructural findings (simultaneous presence of lipid droplets and myofilaments) and immunohistochemical phenotype (small adipocytes were cytokeratin positive).…”