Thymoma mimicking lymphoblastic lymphoma: a pitfall in fine-needle aspiration biopsy interpretation.

Lymphocyte-rich thymoma often contains lymphoblasts and lymphoblastic lymphoma often infiltrates the thymus gland. Although these two neoplasms are clinically distinct in most case, their cytologic features may be similar on biopsy. We describe a fine-needle aspiration biopsy of a thymoma in a 50-yr-old man to increase awareness of this pitfall in cytologic interpretation.