Soft tissue sarcomas that mimic benign lesions

Although it is well known that a variety of benign mesenchymal neoplasms and reactive proliferations may mimic sarcomas, the fact that some types of sarcoma commonly are misinterpreted as benign is less widely appreciated. This review considers five such lesions in soft tissue: low grade fibromyxoid sarcoma, low grade myxofibrosarcoma (myxoid "MFH"), well differentiated liposarcoma (atypical lipoma), epithelioid sarcoma, and so-called inflammatory fibrosarcoma. Principal reasons for their underrecognition are their generally bland cytology, often relative hypocellularity, and indolent clinical course. Common to several of these lesions, however, is a tendency for histological and hence biological progression in local recurrences, underlining the importance of accurate diagnosis and adequate treatment of the primary lesion. This review considers the principal clinicopathologic features, differential diagnosis and (where appropriate) nosologic status of this treacherous group of neoplasms.