Fine-needle aspiration cytology of pseudosarcomatous lesions of soft tissue

Pseudosarcomatous lesions are benign neoplasms of the musculoskeletal syste m that are likely to be misdiagnosed as malignant, based on clinical and hi stologic features. These include soft-tissue "tumors" considered reactive o r reparative lesions such as nodular fasciitis and myositis ossificans. Als o included in the "pseudo-sarcoma" category are benign neoplasms which show "pseudo-anaplastic" cytologic atypia. The latter include lipoma, leiomyoma , angiomyolipoma, and benign peripheral nerve-sheath tumors. These neoplasm s, particularly the reparative processes and the nerve sheath tumors, are i ncreasingly being subjected to initial diagnosis by fine-needle aspiration cytology. Even by conventional cytology this group of lesions represents a well-known pitfall for the diagnostic pathologist. We review some cytologic features: repair-like change, cohesion of cellular fragments, and presence of "normal" elements in the aspirate, which may help the cytopathologist a void misdiagnosis of these notoriously difficult entities. (C) 2001 Wiley-L iss, Inc.