Fine-needle aspiration cytopathology of malignant fibrous histiocytoma

Abstract

BACKGROUND. Most pathologists generally accept malignant fibrous histiocytoma (MFH) as the most common soft tissue sarcoma in adults. This study examines the authors' aspiration cytopathology experience with this 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 diagnosed as such by cytology. RESULTS. Fifty-two cases of MFH (by FNAB or histology) were recovered from the combined files; 42 aspirates had tissue confirmation. Patient age ranged from 1588 years (mean, 63 years); the male:female ratio was 1.2. Thirty aspirates were from primary tumors, and 12 were from recurrences or metastases. From the 29 aspirates diagnosed as MFH, 24 (83%) were determined to be MFH on subsequent 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 cases) or a different sarcoma subtype (2 cases). Eleven of these were histologically diagnosed as MFH, and 2 as other sarcomas. No single cytologic feature or combination of features distinguished MFH. Patterns ranged from single cells to large storiform fragments. Spindled, plasmacytoid, and pleomorphic cell shapes were found; pleomorphic cells were often multinucleated. All cases of MFH had malignant nuclear morphology. Diagnostic pitfalls included low cellularity, obscuring blood and inflammation, and inadequate clinical and/or radiologic information. CONCLUSIONS. The diagnostic role of FNAB in soft tissue lesions remains controversial. FNAB is important in the initial triage of patients with soft tissue tumors, and is particularly accurate for confirming recurrent or metastatic disease. Although making an initial diagnosis of sarcoma by FNAB is reliable, specific subtyping of them as MFH is more problematic.