Hemangioendothelioma with a Prominent Lymphoid Infiltrate Mimicking Follicular Dendritic Cell Tumor: Report of a Case

 Hemangioendothelioma is a vascular tumor with several different morphologic patterns that can include a component of ovoid or spindled cells, but generally lacks an inflammatory component. The combined morphologic and immunohistochemical features are generally sufficient to accurately diagnose this tumor and its many variants. We present a challenging lymphocyte-rich soft tissue lesion that was not recognized to be an unusual hemangioendothelioma until after several recurrences in the arm of a 63 year-old male, which was originally diagnosed as a follicular dendritic cell tumor instead. Local recurrence developed 3 and 11 years later with resections. The most recent tumor consisted predominantly of epithelioid spindled cells with moderate amounts of bubbly pale to eosinophilic cytoplasm with rare discrete cytoplasmic vacuoles, admixed with a prominent lymphoid infiltrate and occasional erythrocytes. The tumor cells were positive for keratin and vascular markers (CD31, CD34, and Factor VIII), but negative for follicular dendritic cell markers (CD21, CD23, CD35). Slides from the two previous excisions were re-analyzed, and showed the same morphologic and immunohistochemical features as the latest recurrence. The diagnosis was revised to recurrent lymphocyte-rich hemangioendothelioma. The patient is free of tumor at 7 years follow-up. This represents an unusual and potentially confusing pattern of hemangioendothelioma that is not previously well described in the literature. Vascular tumors should be included in the differential diagnosis of suspected dendritic cell tumors, even if a lymphocyte-rich infiltrate is present. Vascular as well as dendritic cell markers should be included in the immunohistochemical panel employed in their evaluation. Keyword: Hemangioendothelioma, lymphocyte rich, follicular dendritic cell, tumor.