Aneurysmal ("angiomatoid") fibrous histiocytoma in a child

SOX9 Immunohistochemistry in the Distinction of Angiomatoid Fibrous Histiocytoma From Histologic Mimics: Diagnostic Utility and Pitfalls

Angiomatoid fibrous histiocytoma (AFH) can be diagnostically difficult because of its varied histologic appearance and potential to occur at unusual sites. The identification of recurrent rearrangements (EWSR1-CREB1, EWSR1-ATF1, and FUS-ATF1) is a helpful diagnostic tool. Additional immunohistochemical markers in AFH could aid in restricting the differential diagnosis and selecting appropriate cases for targeted molecular studies. SOX9 is a transcription factor that is crucial for chondrogenesis and is expressed in neoplasms with chondroid differentiation, and other malignant bone and soft tissue tumors. Recently a role of EWS in regulation of SOX9 expression has been reported, the rearrangements typical of AFH may play a role in SOX9 expression. In this study, we analyzed SOX9 expression in 13 pediatric AFH with varying histology, and an additional 80 cases of other myofibroblastic or fibrohistiocytic lesions. SOX9 expression was present in 11 of 13 AFH, 2 of 53 dermatofibroma (1 aneurysmal and 1 cellular) and 1 calcifying aponeurotic fibroma. The remaining tumors were negative. SOX9 is selectively expressed in AFH and may be a useful maker in combination with desmin, CD99, CD68, and EMA in small biopsies, especially in cases with unusual morphologic features. SOX9 appears to be highly specific for AFH, being weakly expressed in a subset of aneurysmal dermatofibroma and absent in other myofibroblastic lesions, except calcifying aponeurotic fibroma. It should be used with caution when differentiating AFH from malignant neoplasms such as Ewing sarcoma.

Aneurysmal Variant of Fibrous Histiocytoma- A Rare Entity Known for Recurrence

Aneurysmal Fibrous Histiocytoma (AFH) is a distinct and a rare clinicopathological variant of Cutaneous Fibrous Histiocytoma (CFH). It differs from the usual benign fibrous histiocytoma clinically and morphologically with high rate of recurrence. Here, we report a case of AFH with history of recurrence which presented as a polypoid swelling and showed vascular spaces with no endothelial lining which was proved negative by CD34 immunostaining. The spaces were bordered by tumour cells.

Angiomatoid variant of fibrous histiocytoma: a case report and review of literature

Fibrous histiocytomas by themselves are not very common in the head and neck region. Apart from considering the above fact, this report describes a unique and relatively rare variant of the neoplasm - the angiomatoid fibrous histiocytoma (AFH) which has a characteristic appearance and predilection for young individuals that occurred in the left lower border of the mandible in a 13-year-old girl. Angiomatoid fibrous histiocytoma is a distinct fibrohistiocytic tumour of children and young adults that combines features of both fibrohistiocytic and vascular neoplasm. It is considered to be a tumour of intermediate malignancy because of its less aggressive course in contrast to the conventional malignant fibrous histiocytoma. The authors would like to stress upon the fact that clinicians should not overlook swellings that may not appear distinct visually and therefore consider it to be a part of normal anatomy, dismiss it as an anomaly with no significance, or treat it injudiciously, for ultimately it may prove to be a tumour that would require appropriate treatment and follow-up.

Genetic characterization of angiomatoid fibrous histiocytoma identifies fusion of the FUS and ATF-1 genes induced by a chromosomal translocation involving bands 12q13 and 16p11

This case report documents the first karyotypic, fluorescence in situ hybridization, and genetic analysis of an angiomatoid fibrous histiocytoma that arose and recurred in the arm of a 5.5-year-old girl. Complex rearrangements between chromosomes 2, 12, 16, and 17 were noted, as well as deletion in the long arm of chromosome 11. Flow cytometry revealed a normal cell population. The t(12;16) site was further investigated using reverse transcriptase-polymerase chain reaction. We found that the FUS (also known as TLS) gene from 16p11 combined with the ATF-1 gene from 12q13 to generate a chimeric FUS/ATF-1. The FUS gene is rearranged in the t(12;16)(q13;p11) that characterizes myxoid liposarcoma and in acute myeloid leukemia with t(16;21)(p11;q22), while the ATF-1 gene is rearranged in the t(12;22)(q13;q12) found recurrently in clear cell sarcomas (malignant melanoma of soft parts). Thus, the FUS/ATF-1 gene in angiomatoid fibrous histiocytoma is predicted to code for a protein that is very similar to the chimeric EWS/ATF-1 found in clear cell sarcoma.