Angiomatoid fibrous histiocytoma including cases with pleomorphic features analysed by fluorescence in situ hybridisation.

BACKGROUND: Angiomatoid fibrous histiocytoma (AFH) is a rare soft-tissue tumour of uncertain differentiation and low metastatic potential. Cytogenetics and/or molecular genetics have revealed that most have a rearrangement of the EWSR1 gene, whereas a FUS gene rearrangement is present in a minority of cases. Although some cases of AFH display striking pleomorphism and mitotic activity, there are no known clinical, morphological or genetic factors that predict metastasis. The authors present clinicopathological features of AFH, including cases showing a pleomorphic histological appearance, and results of fluorescence in situ hybridisation analysis of EWSR1 and FUS rearrangements.
METHODS: Tumour samples from 10 patients were subjected to clinicopathological and immunohistochemical analysis and dual-colour fluorescence in situ hybridisation for EWSR1 and FUS with split-signal probes.
RESULTS: All cases showed clinical features (sites: extremities followed by trunk; age: adolescent to young adult), morphology (multinodular proliferation of spindle cells, lymphoid cuffs and pseudovascular spaces) and immunohistochemical results (more than half were positive for CD68, CD99, desmin and epithelial membrane antigen) typical of AFH. There were two local recurrences in each of two patients. Two patients developed distant metastases and died from the disease; tumours of these two patients showed focal proliferation of large pleomorphic cells with hyperchromatic nuclei and high proliferative activity (>10/10 high-power field and Ki-67 labelling index >10%). There were no clinical, histological or immunohistochemical differences between the nine cases with EWSR1 rearrangement and one case with FUS rearrangement.
CONCLUSIONS: Wide surgical excision and careful follow-up are necessary for patients with AFH in view of its risk of local recurrence and metastasis leading to a fatal outcome.