FINE-NEEDLE ASPIRATION CYTOPATHOLOGY OF MALIGNANT FIBROUS HISTIOCYTOMA

BACKGROUND. Most pathologists generally accept malignant fibrous histi ocytoma (MFH) as the most common soft tissue sarcoma in adults. This s tudy examines the authors' aspiration cytopathology experience with th is tumor, describes its cytomorphology, and determines the reliability of such a diagnosis by fine-needle aspiration biopsy (FNAB). METHODS. The authors' files were reviewed for cases diagnosed as MFH by FNAB, and for surgical pathology cases of MFH previously aspirated but not d iagnosed as such by cytology. RESULTS. Fifty-two cases of MFH (by FNAB or histology) were recovered from the combined files; 42 aspirates ha d tissue confirmation. Patient age ranged from 15-88 years (mean, 63 y ears); the male:female ratio was 1.2. Thirty aspirates were from prima ry tumors, and 12 were from recurrences or metastases. From the 29 asp irates diagnosed as MFH, 24 (83%) were determined to be MFH on subsequ ent surgical excision. Four of the remaining cases were other sarcoma subtypes, and there was one organizing thrombus (false-positive). The remaining 13 aspirates were identified as unqualified sarcoma (11 case s) or a different sarcoma subtype (2 cases). Eleven of these were hist ologically diagnosed as MFH, and 2 as other sarcomas. No single cytolo gic feature or combination of features distinguished MFH. Patterns ran ged from single cells to large storiform fragments. Spindled, plasmacy toid, and pleomorphic cell shapes were found; pleomorphic cells were o ften multinucleated. AU cases of MFH had malignant nuclear morphology. Diagnostic pitfalls included low cellularity, obscuring blood and inf lammation, and inadequate clinical and/or radiologic information. CONC LUSIONS. The diagnostic role of FNAB in soft tissue lesions remains co ntroversial. FNAB is important in the initial triage of patients with soft tissue tumors, and is particularly accurate for confirming recurr ent or metastatic disease. Although making an initial diagnosis of sar coma by FNAB is reliable, specific subtyping of them as MFH is more pr oblematic. (C) 1997 American Cancer Society.