Malignant thymoma in a patient with HIV positivity: a case report with a review of the differential cytologic diagnoses.

A 33-yr-old African-American male with known human immunodeficiency virus (HIV) positivity underwent CT guided fine-needle aspiration biopsy of an anterior mediastinal mass. The aspirate was composed of a dimorphic population of cells that included small mature lymphoid cells and scattered cohesive groups of large epithelial cells in equal numbers. The neoplasm stained strongly for low weight molecular cytokeratin, epithelial membrane antigen (EMA), leukocyte common antigen (LCA), and Leu-7 which was consistent with a diagnosis of thymoma. Subsequent biopsies determined the neoplasm to be a malignant (invasive) thymoma. This case emphasizes the efficacy of FNA biopsy for the evaluation of anterior mediastinal masses in HIV infected individuals. Additionally, the differential cytologic diagnoses for HIV infected individuals for this anatomic site are discussed.