Pleomorphic sarcomas: subclassification, myogenic differentiation and prognosis

Pleomorphic soft tissue sarcomas (STS) in adults comprise a wide range of neoplasms which can be separated into two categories: those showing myogenic differentiation (e.g. pleomorphic leiomyosarcoma and pleomorphic rhabdomyosarcoma) and those lacking this feature (e.g. myxofibrosarcoma and extraskeletal osteosarcoma). Most are high-grade, aggressive STS, although a subset belongs to the low-grade category (e.g. myxoinflammatory fibroblastic sarcoma and pleomorphic hyalinizing angiectatic tumour). Except for dedifferentiated liposarcomas, myogenic differentiation in pleomorphic sarcomas is an adverse prognostic factor, being associated with more aggressive behaviour and higher metastatic rate. Histological subtype, large size, high tumour grade, deep situation, vascular invasion, location outside the limbs and previous history of tumour recurrence(s) are additional negative prognostic indicators. This review will focus on the salient pathological, molecular and prognostic characteristics of the most common myogenic and non-myogenic pleomorphic STS.