Evidence of BRAF V600E in indeterminate cell tumor and interdigitating dendritic cell sarcoma

Abstract BRAF V600E mutations have been reported in several histiocytic and dendritic cell neoplasms. In this case series, we report BRAF V600E–positive histiocytic and dendritic cell neoplasms in association with lymphomas and lymphoid proliferations. This is a review of cases with immunohistochemistry for BRAF V600E, with additional immunohistochemistry to categorize tumors. We report the first case of BRAF V600E–positive indeterminate cell tumor in association with angioimmunoblastic T-cell lymphoma. We also report a case of BRAF V600E–positive interdigitating dendritic cell sarcoma in a patient with positive B-cell polymerase chain reaction. It is unclear if these neoplasms developed as transdifferentiation of lymphoid neoplasms or if they developed independently. These cases illustrate the expanding spectrum of BRAF V600E–positive histiocytic and dendritic cell tumors and suggest that attention should be paid to lymphomas for possible coincident presentation of these disorders.