Chondroid lipoma, a rare lipomatous tumor: A case series

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Introduction: Chondroid lipoma is a rare, benign lipomatous tumor that may be mistaken histologically for a liposarcoma or chondrosarcoma. Herein, two cases of chondroid lipoma are reported in two Egyptian females aged 38 and 51 years and literature about this rare tumor briefly reviewed with discussion of diagnostic criteria that may help distinguish it from other tumors with overlapping histologic features. Case Series: The tumor was subcutaneous in both cases. One was located in the right knee area, the other in an infra-mammary location on the right side of the chest. Grossly, both neoplasms were encapsulated and exhibited a nodular, myxoid cut surface. Histologically, they consisted of an abundant myxoid and chondroid stroma interspersed by small round cells with eosinophilic or vacuolated cytoplasm, signet ring lipoblast-like cells, adipocytes and foci of mature adipose tissue. Immunohistochemically, diffuse reactivity of the neoplastic cells for vimentin and variable reactivity for S-100 protein were present in both cases. One case also showed focal immunoreactivity for CD68. The Ki67 proliferative index was less than 5%. The common differentials like myxoid liposarcoma and extraskeletal myxoid chondrosarcoma were ruled out based mainly on pure histologic criteria. Both patients underwent simple curative excision and were tumor free for at least one and three years after surgery, respectively. Conclusion: Because chondroid lipoma is easily misdiagnosed as a sarcoma of either adipose tissue or cartilage, a high level of suspicion by the pathologist and familiarity with its features are of practical importance to avoid misdiagnosis and overtreatment.