COLON, RIGHT, HEMICOLECTOMY:
R. Cardier first described gastrointestinal neuroendocrine tumors that contain an additional glandular component in 1924. Meanwhile, a number of similar cases have been reported using terms such as goblet cell carcinoid, composite carcinoid, adenocarcinoid, and small cell undifferentiated carcinoma which has led to confusion among clinicians and pathologists. These tumors are morphologically recognizable as having both glandular and neuroendocrine differentiation.
In the 2000 WHO classification of endocrine tumors, such neoplasms were defined as mixed exocrine-endocrine tumors when each component represents at least 30% of the lesion . It is worth noting that adenocarcinomas with scattered neuroendocrine cells are not categorized as mixed exocrine-endocrine tumors, neither are neuroendocrine neoplasms with a focal glandular component since in most cases less than 30% of each component is present. Mixed exocrine-endocrine tumors are rare and are believed to account for less than 3% of colorectal neoplasms.
In 2010, the WHO classification for this neoplasm was again redefined as mixed adenoneuroendocrine carcinomas (MANECs). They may also be further classified as collision and composite types; where collision tumors consist of two different histologic patterns in close contact, and composite tumors composed of endocrine and exocrine cells that are intermixed within the same tumor.
The clinical significance of focal neuroendocrine differentiation in gastrointestinal adenocarcinomas is still somewhat debatable. Gastrointestinal mixed adenoneuroendocrine carcinomas (MANECs ) are a heterogeneous group of tumors showing different morphological, clinical, and prognostic features and can be grouped in different categories according to the grade of malignancy of each component . When considering treatment, the more aggressive component of MANECs should be taken into consideration. Adenoneuroendocrine carcinomas containing a well differentiated neuroendocrine component and a glandular component should be treated as adenocarcinomas, whereas if a poorly differentiated neuroendocrine component is present, it should be treated as a gastrointestinal neuroendocrine carcinoma.
Contributed by Richard Freij, MD and Eizaburo Sasatomi, MD, PhD