Carcinoid tumors

Abstract

Carcinoid tumors are rare, slow-growing neuroendocrine tumors arising from the enterochromaffin cells disseminated throughout the gastrointestinal and bronchopulmonary systems. Though they have been traditionally classified based on embryologic site of origin, morphologic pattern, and silver affinity, newer classification systems have been developed to emphasize the considerable clinical and histopathologic variability of carcinoid tumors found within each embryologic site of origin. These neoplasms pose a diagnostic challenge because they are often innocuous at the time of presentation, emphasizing the need for a multidisciplinary diagnostic approach using biochemical analysis, standard cross-sectional imaging, and newer advances in nuclear medicine. Similarly, treatment of both primary and disseminated carcinoid disease reflects the need for a multidisciplinary approach, with surgery remaining the only curative modality. The prognosis for patients with these tumors is generally favorable; however, it can be quite variable and is related to the location of the primary tumor, extent of metastatic disease at initial presentation, and time of diagnosis.

Figure 1. Cross sectional imaging of a carcinoid tumor

(A) CT of the chest showing a solitary left-sided pulmonary carcinoid tumor. Well-differentiated (typical) pulmonary carcinoid tumors represent nearly two-thirds of all bronchopulmonary carcinoid neoplasms and are commonly found in the perihilar region. (B) CT of the abdomen showing multiple liver metastases in a patient with metastatic carcinoid disease. (C) CT scan showing the typical appearance of a small bowel carcinoid, represented by a mesenteric soft tissue mass with radiating strands.

Figure 1. Cross sectional imaging of a carcinoid tumor

(A) CT of the chest showing a solitary left-sided pulmonary carcinoid tumor. Well-differentiated (typical) pulmonary carcinoid tumors represent nearly two-thirds of all bronchopulmonary carcinoid neoplasms and are commonly found in the perihilar region. (B) CT of the abdomen showing multiple liver metastases in a patient with metastatic carcinoid disease. (C) CT scan showing the typical appearance of a small bowel carcinoid, represented by a mesenteric soft tissue mass with radiating strands.

Figure 2. Carcinoid tumor of the small intestine

These tumors are fairly well circumscribed but not encapsulated, white or pale yellow tan, and very firm due to a marked desmoplastic reaction. Carcinoid tumors of the small intestine are frequently associated with mechanical obstruction of the intestine as a result of extensive mesenteric fibrosis (shown here).