[20] Angiomatoid Fibrous Histiocytoma: An Expansion of the Histologic Spectrum

Summer L Bohman, Brian P Rubin, John R Goldblum, Munir R Tanas, Steven D Billings. Cleveland Clinic Foundation, Cleveland

Background: Angiomatoid fibrous histiocytoma (AFH) is a tumor of intermediate malignancy that usually presents on extremities of children/young adults. Classically, AFH is composed of histiocyte-like cells with round to oval nuclei with pseudovascular spaces, hemorrhage and hemosiderin and is surrounded by a fibrous pseudocapsule with a peripheral lymphocytic cuff. AFH frequently have translocations involving EWSR1, or less commonly FUS. Morphologic variants have been described, but some cases of AFH cause diagnostic difficulty and this tumor is a frequent source of consultation. We reviewed our experience with AFH and emphasize unusual histologic features.
Design: Detailed histologic examination was performed, evaluating classic features, unusual features and mitotic rates. In cases with blank slides/blocks, immunostains for CD68, desmin and EMA and FISH for the EWSR1 translocation were performed. Demographics were also reviewed.
Results: 26 cases met selection criteria. A broad morphologic spectrum was observed. In addition to classic histologic features, 9 cases displayed various degrees of sclerosis with 3 displaying a focal swirling perineurioma-like pattern, with 1 having a diffuse perineurioma-like pattern. Nine cases had at least moderate pleomorphism, with 2 having striking pleomorphism. 8 had eosinophils, one with numerous eosinophils throughout the tumor. Atypical mitotic figures were seen in 3, including two pleomorphic AFHs and the case with numerous eosinophils. One had reticular/myxoid morphology. Evidence of a EWSR1 translocation was seen in 11/15 tested. One pleomorphic AFH was aneusomic for EWSR1, suggesting a cryptic translocation. Immunohistochemically, 69% expressed EMA, 53% desmin and 63% CD68. With the exception of one case, all had ≥2 of the classic findings: peripheral lymphocytic cuff, fibrous pseudocapsule, pseudovascular spaces, hemorrhage and hemosiderin. The single exception only had a lymphocytic cuff. In review of the demographics data, 5 (19%) occurred in patients >40 years old, and 9 (35%) were located outside the extremities. Three (12%) occurred in patients >40 years old and in atypical locations.
Conclusions: AFH has a broader histologic and clinical spectrum than is commonly recognized. In addition to conventional features, sclerosis, perineurioma-like areas, marked eosinophilia, atypical mitotic figures, marked pleomorphism, and complex cytogenetic aberrations involving EWSR1 may be seen. Many typical histologic features may be absent. Knowledge of this morphologic spectrum with utilization of FISH is helpful in AFH with unusual features.
Category: Bone & Soft Tissue

Monday, March 19, 2012 1:00 PM

Poster Session II # 21, Monday Afternoon


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