Ectopic adrenocorticotropic hormone syndrome caused by neuroendocrine carcinoma of the colon.

A 48-year-old woman with a history of autoimmune hemolytic anemia and taking long-term corticosteroid therapy presented with a 3-month history of general fatigue, abdominal distension, and pigmentation. A computed tomography scan of the abdomen showed a tumor in the sigmoid colon and multiple metastatic nodules in the liver. A colonoscopy revealed an obstructing mass with the presence of an irregular ulcer in the sigmoid colon. Following biopsy and histopathological analysis, the patient was diagnosed with neuroendocrine carcinoma (NEC) of the colon. She received her first cycle of chemotherapy, with carboplatin and etoposide. During hospitalization, her pigmentation and hypertension worsened and hypokalemia was observed, all of which suggsted Cushing's syndrome. Her plasma adrenocorticotropic hormone (ACTH) and cortisol levels were high, and an ectopic ACTH-producing tumor was suspected. After a second chemotherapy cycle, she developed neutropenic fever and subsequently died. At autopsy, two histological types were found in the tumor: small cell carcinoma and large cell NEC. Immunohistochemical analysis revealed ACTH in the large cell NEC. This is the first reported case of an ectopic ACTH syndrome caused by NEC of the colon.