Adrenocorticotropic hormone-producing thymic neuroendocrine carcinoma with oncocytic features: A case report and review of literature

Thymic neuroendocrine carcinomas are the most common mediastinal neuroendocrine tumor. These malignancies are not often diagnosed by fine-needle aspiration (FNA), as they are more commonly diagnosed by biopsy or excision. We describe a case of a FNA of a paratracheal mass from a 38-year-old man who presented with Cushing syndrome. A low-grade neuroendocrine carcinoma with oncocytic features was diagnosed, which was later confirmed by excision of the thymus, anterior mediastinal and paratracheal soft tissue, and lymph nodes. Oncocytic features in these tumors are a rare finding and bring metastatic medullary thyroid carcinomas as well as other metastases into the differential diagnosis. The prognosis of neuroendocrine carcinomas in this location is worse than neuroendocrine carcinomas in other areas, and close follow-up is recommended.