Angiomatoid fibrous histiocytoma a series of five cytologic cases with literature review and emphasis on diagnostic pitfalls.

Angiomatoid fibrous histiocytoma (AFH) is an uncommon and mostly indolent soft tissue neoplasm, which usually occurs in the subcutaneous tissue of the extremities in children and young adults. Although the histologic features of AFH are well established, reports of its cytomorphology are very limited. This report characterizes the cytomorphologic features of five cases of AFH, with correlation to clinical, histology, and cytogenetic findings. Smears of fine needle aspiration (FNA; four cases) and intraoperative scrape (one case) were reviewed from five patients with a histologically confirmed diagnosis of AFH. A review of six previously reported AFH cases with cytomorphology was also performed. The tumor presented as a cystic, deep dermal mass in three pediatric cases and as a solid, deeply seated mass in two adults. The cytomorphologic features are mostly nondistinctive and include cellular smears with ovoid to spindled histiocytoid cells that may be isolated or in clusters. Some of these cells are atypical and others contain hemosiderin. Large cellular clusters with a capillary structure and a whorled arrangement of tumor cells can be appreciated in some cases. There is always a bloody background, but a lymphoplasmacytic infiltrate is uncommon. The presences of EWSR1 rearrangement in one case and three copies of FUS gene in another case were detected by fluorescence in situ hybridization. Diagnosing AFH by FNA cytology alone can be challenging because of its rarity and usually nonspecific cytologic findings. Clinical correlation and ancillary studies are essential to reach a specific diagnosis of AFH in small needle biopsies.