Incidental finding of abdominal splenosis with mononucleated cell infiltration leading to a diagnosis of acute myeloid leukemia.

Splenosis refers to ectopic splenic implants that are often found incidentally years after splenic rupture/splenectomy, and the nodules of splenosis are usually small, less than 3 cm for the majority. We report a case of splenosis with a 5-centimeter large mass in the anterior abdomen in a 79 year-old male with a remote history of splenic rupture/splenectomy. Unexpectedly, needle core biopsy of the abdominal mass demonstrated splenic tissue with a mononucleated cell infiltrate blurring the splenic architecture that was highlighted only by CD8 stain. This finding prompted a bone marrow examination resulting in the diagnosis of acute myeloid leukemia in the patient. Retrospectively, enlargement of this ectopic spleen may have been caused by this leukemic infiltrate. This case underscores the importance of being aware of this rare pathological condition and its retained vulnerability for involvement by hematolymphoid neoplasms, as well as significance of identifying splenic architecture highlighted by CD8 stain to reach a correct diagnosis.