Myeloid sarcoma diagnosed on pleural effusion cytology: A case report and literature review

Myeloid sarcoma (MS) is a mass-forming, extramedullary infiltration of myeloid blasts rarely presenting in cases of acute myeloid leukemia (AML). These tumoral masses rarely occur at any and multiple anatomic sites, precedent or coincident with bone marrow evidence of AML. We report a case of MS that presented as pancreatic and cardiac masses where subsequent evaluation of pleural effusion cytology rendered the diagnosis. Primary MS diagnosed via pleural effusion cytology is not yet reported in literature. Herein, we report the case of a 45-year-old man who presented with abdominal pain. An infiltrative mass was identified in the pancreatic head, suspicious for pancreatic adenocarcinoma. Despite multiple attempts, Fine needle aspiration cytology of the pancreatic mass failed to render a definitive diagnosis. Subsequent thoracentesis of a right pleural effusion revealed cytologically malignant cells, identified as myeloid blasts after immunohistochemical and flow cytometric evaluation. Although rare, MS should be considered as a diagnostic possibility in the evaluation of malignancy with an unknown primary.