Small lymphocytic lymphoma/chronic lymphocytic leukemia in a pelvic myelolipoma

Myelolipoma is a rare benign tumor composed of mature adipose tissue and normal hematopoietic elements. Extra-adrenal myelolipomas are extremely rare, with approximately 50% of cases occurring in the presacral region. We report a case of an 85 year old woman who presented with small bowel obstruction relating to a pelvic mass detected on computed tomography (CT) scan. At laparotomy, a 12-cm. pre-sacral mass was resected. Histologic examination showed a myelolipoma with dense lymphoid aggregates. On immunostains, the lymphoid aggregates showed positivity for CD20, CD5, and CD23, consistent with small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). Molecular evaluation confirmed the presence of a clonal B-cell lymphocytic proliferation that did not harbor BCL-2 or BCL-1 gene rearrangements. This case represents the first report of a myelolipoma involved by a non-Hodgkin lymphoma. The unique combination of these findings raises questions about the relationship between the two observed entities. The likeliest scenario is that an unusual benign tumor (myelolipoma) was colonized by a relatively common systemic hematopoietic neoplasm SLL/CLL, producing a collision tumor.