Thymic adenocarcinoma presenting as an incidental mediastinal mass

BACKGROUND: Primary thymic adenocarcinoma represents an exceptionally rare malignancy, for which the cornerstone of therapy is margin-negative resection, with radiation and systemic therapy reserved for invasive and advanced disease. Thymic adenocarcinoma has not been previously reported in the setting of a concomitant malignancy, as reported herein. CASE PRESENTATION: We present a case of a 55-year-old previously healthy male diagnosed with acute myeloid leukemia, also found to have a mediastinal mass. Evaluation of the mediastinal mass with tumor markers, biopsies, and next-generation sequencing proved non-diagnostic, while he was simultaneously treated with induction chemotherapy to prevent leukemia-related blast crisis. After completing and recovering from induction chemotherapy, he underwent successful thymectomy during a chemotherapy holiday, with a margin-negative resection of thymic adenocarcinoma. He has subsequently recovered and undergone successful allogeneic hematopoietic stem cell transplant. CONCLUSIONS: We present a case of synchronous adult acute myeloid leukemia and primary thymic adenocarcinoma requiring a tailored approach for management of simultaneous malignancies.