Sclerosing extramedullary hematopoietic tumor presenting as an inguinal mass in a patient with primary myelofibrosis: a diagnostic pitfall.

Sclerosing extramedullary hematopoietic tumor (SEMHT) is a rare lesion and presented as retroperitoneal or serosal-based mass. A 53-year-old man with a long history of primary myelofibrosis, presented with abdominal distension and inguinal mass. Pathologic examination of inguinal mass revealed a prominent sclerotic background with thick collagen deposits and mono, bi, or tri-lineage hematopoietic tissue containing atypical megakaryocytes and variable proportions of myeloid and erythroid series. The atypical megakaryocytes were positive for Factor VIII and CD61. SEMHT may be misdiagnosed as lymphocyte depleted Hodgkin's disease, as a mesenchymal neoplasm, or as carcinoma, because of the presence of large atypical cells and marked fibrosis when clinical information regarding PMF is unknown. Awareness of the bizarre atypical megakaryocyte morphology with immature hematopoietic cells and of clinical history is essential to prevent misdiagnosis.