Cytopathology of myxoinflammatory fibroblastic sarcoma: a series of eight cases and review of the literature

Introduction: Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare low-grade sarcoma presenting as a slow-growing mass that occurs mainly in the distal extremities of adults. Relatively little is known about the cytopathology of MIFS. We evaluated cytologic characteristics of MIFS on fine-needle aspiration (FNA). Materials and methods: A search was made of our cytopathology and surgical pathology databases for cases diagnosed as MIFS. FNA biopsy smears and cell-block were performed and examined using standard technique. Results: Eight cases were retrieved from patients aged 22-90 years (mean, 56 years), and M:F ratio of 1:1. Six tumors (75%) were primary, and 2 (25%) locally recurrent. Distal lower limb was involved in all but one case (88%). One (13%) recurrent case was correctly diagnosed cytologically as MIFS; remaining single diagnoses were varied: myxofibrosarcoma, low-grade sarcoma, malignant neoplasm, myxoid neoplasm, atypical fibrohistiocytic neoplasm, atypical cells with chronic inflammation, and spindle cells with atypia. Among 7 cases with available cytologic slides for review, common features were spindle cells with variable atypia (100%), rare virocyte/Reed-Sternberg -like cells (86%), background mixed inflammation (71%), and variable myxoid stroma (57%). Pseudolipoblasts and multinucleated giant cells were rare. Hemosiderin and branching capillaries were largely absent. Immunohistochemistry was non-specific. Conclusion: MIFS was accurately interpreted in only 13% of cases; remaining cases were diagnosed as atypical or malignant, which would lead to proper management. A specific cytologic diagnosis of MIFS using FNA is extremely difficult in our experience due to an absence of distinctive cytomorphology and specific immunophenotype.