Angiomatoid fibrous histiocytoma: an expansion of the clinical and histological spectrum

Angiomatoid fibrous histiocytoma, a fibrohistiocytic tumour of intermediate malignancy that usually presents on extremities of young patients, has a broader clinical/histological spectrum than is widely appreciated. We summarise our experience with an emphasis on unusual features. Twenty-seven cases were analysed for clinical and histological features, including immunohistochemistry and FISH for rearrangements of EWSR1 or FUS. Five (19%) occurred in patients >40 years old, and ten (37%) occurred outside the extremities. Three that occurred in patients >40 years old arose in atypical locations. Evaluation for classical histological features (lym-phocytic cuff, fibrous pseudocapsule, pseudovascular spaces, haemorrhage, haemosiderin, and histiocytoid morphology) showed that all had two or more classical features. Unusual features were noted in many cases. Ten (37%) displayed significant areas of sclerosis; three of these ten had areas with a perineurioma-like pattern. Nine displayed at least moderate pleomorphism, with two exhibiting striking pleomorphism. Eight had eosinophils in the stroma, one with numerous eosinophils. One had a reticulated pattern of cells in a myxoid stroma. Mitotic rates were low [average 0.67/10 high power fields (HPFs)]. Three had atypical mitotic figures. Thirteen of 20 (65%) were CD68 positive, 11 of 17 (65%) were EMA positive, and 10 of 18 (56%) were desmin positive. Thirteen of 16 (81%) had a rearrangement of EWSR1; none had a FUS rearrangement. This series expands the spectrum of angiomatoid fibrous histiocytoma.