[Chondroid lipoma. Clinicopathological, immunohistochemical, and ultrastructural analysis of six cases of a distinct entity in the spectrum of lipomas].

A series of six cases of chondroid lipoma is reported in this paper. The age of the patients, four women and two men, ranged from 34 to 75 years. Four tumours arose in the lower and two in the upper extremities between 4.5 and 8 cm in size. Whereas two neoplasms were located in the subcutis, four lesions were seen in perifascial or intramuscular tissues. Histologically, all neoplasms were encapsulated and characterized by a somewhat lobular growth pattern. The neoplasms were composed of mature adipocytes, uni - and multivacuolated lipoblasts, and nests and strands of cells reminiscent to hibernoma cells or chondrocytes. Immunohistochemically and ultrastructurally the lipogenic nature of the latter type of cells was confirmed. Interestingly, focal immunopositivity of tumour cells for cytokeratin was found in two cases. Tumour cells were set in a myxohyaline matrix showing different degrees of degeneration. Chondroid lipoma represents a distinct entity in the spectrum of lipomatous lesions and has to be distinguished from benign and malignant neoplasms (extraskeletal chondroma, hibernoma, lipoblastoma, chondrolipoangioma, myoepithelioma, myxoid/round cell liposarcoma, and extraskeletal myxoid chondrosarcoma). Because they are easily misdiagnosed as malignant tumours, familiarity with the features of chondroid lipoma is of practical importance to avoid an overtreatment.