Atypical Carcinoid Tumor of the Thymus: A Rare Case Report

Abstract

Neuroendocrine tumors (NETs) of the thymus are exceedingly unusual neoplasms, accounting for approximately 0.4% of all carcinoid tumors and less than 5% of all the anterior mediastinal neoplasms. Atypical carcinoid of the thymus originates from cells of the diffuse neuroendocrine system within the thymus. Its estimated annual incidence is approximately 0.18 cases per 1,000,000 individuals. Just over 100 cases have been published worldwide till date, thereby emphasizing its rarity. Herein, we present a case of a 35-year old female with generalized weakness, difficulty in breathing, facial puffiness, acne, buffalo hump, proximal myopathy, easy bruisability, and weight loss. She was a known type 2 diabetes mellitus patient with central hypothyroidism and Cushing’s syndrome. Computed tomography revealed a well-defined soft-tissue lesion in the anterior mediastinum. A complete thymectomy was performed. Histopathological examination substantiated by immunohistochemistry (IHC) confirmed the diagnosis of primary thymic atypical carcinoid. Our case report describes an extremely rare entity, and it definitely adds on to the existing literature in account of its rarity. It highlights the importance of histopathological examination in conjunction with IHC to arrive at the final diagnosis. Additionally, in this case report, we have also proved ectopic Cushing’s syndrome by using the adrenocorticotropic hormone (ACTH) IHC marker on tumor tissue, which in difficult cases can be helpful to confirm the presence of ACTH secretion in tumors.