Multiple pulmonary atypical carcinoids presenting with long-standing Cushing syndrome masked by pulmonary tuberculosis

Pulmonary neuroendocrine tumors, especially small cell carcinoma and typical carcinoids, are the most common cause of ectopic Cushing syndrome (CS). Sometimes these adrenocorticotropic hormone (ACTH)-producing tumors are too small to localize, and it may take a long time to identify them. This report describes the case of a 27-year-old-man with CS. This CS was due to the ectopic ACTH produced by the pulmonary atypical carcinoids, which were recognized at the disseminated stage 5 years after the initial presentation of CS. Microscopically, multiple whitish nodules (up to 1.0 cm in diameter) of the wedge-resected lung were composed of small round cells appearing to be typical neuroendocrine but were diagnosed as atypical carcinoid, based on the findings of focal necrosis, high mitotic rates and multiple endolymphatic tumor emboli. Immunohistochemically, tumor cells robustly stained for ACTH. The delay of diagnosis is, in part, attributable to the pulmonary tuberculosis (one of the complications of hypercortisolism), because the pulmonary tuberculosis presented in the form of multiple nodules throughout the lung. In addition, this patient had a Crooke's cell hyperplasia of the pituitary gland, which represents the reactive change of corticotrophs exposed to the excess cortisol rather than neoplastic change leading to CS.