Successful Treatment of a Mixed Neuroendocrine-Nonneuroendocrine Neoplasm of the Colon with Metastases to the Thyroid Gland and Liver

Patients with mixed neuroendocrine-nonneuroendocrine neoplasms (MiNENs) of the colon have poor prognosis. Herein, we report a patient with MiNEN of the colon with metastases to the liver and the thyroid gland, with long-term survival. A 45-year-old man presented with anterior neck swelling. Histopathological examination of the thyroid tumor revealed neuroendocrine carcinoma (NEC), suggesting that a primary NEC in another organ had metastasized to the thyroid gland. Computed tomography to identify a primary NEC revealed two tumors: one in the liver and one in the transverse colon. A biopsy revealed that the histopathology of the liver and colon tumors was NEC and adenocarcinoma, respectively. Thereafter, the patient underwent surgical resection of the colon tumor and was finally diagnosed as colon MiNEN with metastases to the thyroid and liver. The surgical resection of the metastatic liver tumor was performed after several courses of systemic chemotherapy, and the patient survives presently without any recurrence for approximately seven years after the diagnosis. Surgical resection of each metastatic lesion combined with systematic chemotherapy apparently improved the prognosis of MiNEN of the colon with distant metastases.