Cytodiagnostic features of angiofibroma of soft tissue: A review of 16 cases to identify characteristic findings and their diagnostic significance

BACKGROUND: Angiofibroma of soft tissue (AFST) is a rare benign fibroblastic/myofibroblastic neoplasm. Despite several published studies describing the clinicopathological features of AFSTs, its cytological characteristics remain poorly documented. This study aimed to identify distinctive cytological features that may support accurate diagnosis. METHODS: The authors reviewed 16 histologically confirmed AFST cases diagnosed at their institution between 2007 and 2025. The cytological specimens were evaluated for stromal composition, vascular patterns, cellularity, and cytomorphology. Fluorescence in situ hybridization (FISH) analysis was performed to detect the AHRR::NCOA2 or AHRR::NCOA3 gene fusions. RESULTS: The median age of the patients was 58 years, with a female predominance. The tumors occurred predominantly in the lower extremities. Cytologically, exclusively collagenous stroma (62.5%), mixed collagenous/myxoid stroma (31.2%), and purely myxoid stroma (6.2%) were observed. Two distinctive vascular patterns were identified: protruding small vessels at the margin of cell clusters (87.5%) and reticular vascular networks (43.8%), which were frequently identified in the cases with myxoid stroma (83.3%). Under the World Health Organization Reporting System for Soft Tissue Cytopathology, 12 cases (75%) were classified in nonbenign categories (soft tissue neoplasm of uncertain malignant potential [STNUMP], 62.5%; atypical, 12.5%). AHRR::NCOA2 fusion was identified in 14 cases and AHRR::NCOA3 in the remaining two cases. CONCLUSION: AFST poses significant diagnostic challenges in cytological practice. Recognition of these two characteristic vascular patterns within distinct stromal backgrounds is essential for differentiating AFST from other spindle cell and myxoid neoplasms of intermediate-to-malignant biological behavior, thereby improving diagnostic accuracy.