Rectal carcinoid tumors: how well do endoscopic ultrasonography (EUS) appearances correspond to histological findings?

Aim: EUS has often informed us about the detailed nature of submucosal tumors of the gastrointestinal tract. We evaluate the relationships between EUS patterns and histological findings of rectal carcinoid tumors.

Patients and Methods: Between January 1995 and January 2006, 17 cases of rectal carcinoid tumor were experienced at the Center Building Clinic. There were 8 males and 10 females with their age ranging from 37 to 72. All the tumors were detected by colonoscopy. Of these, EUS (EU-M30 and probe 20 and/or 30MHz, Olympus, Tokyo, Japan) was applied to 15 lesions of 15 cases. Internal echo patterns of the carcinoids were classified into nodular high echo pattern, fine high echo pattern, and very fine high echo pattern. The resected specimens were examined histologically, and the findings were classified into subgroups by cellular/stromal density of the tumors.

Results: The tumor size ranged from 2–10mm with an average of 5.4mm. Application of EUS confirmed the existence and depth of the tumor even in cases of diminutive 2–3mm lesions. All carcinoid tumors were shown as low echoic submucosal lesions. Nodular high internal echo patterns in the low echoic lesion on EUS reflected sparse carcinoid cell nests and low stromal density histologically. Fine high internal echo patterns showed medium carcinoid cells and medium stromal density. Very fine internal echo patterns in the low echo mass corresponded either to dense carcinoid cells and high stromal density or to sparse carcinoid cells and high stromal density.

Conclusion: EUS is very useful to ascertain the existence of diminutive carcinoid tumor and to determine the depth of tumor in the rectal wall. In addition, EUS appearances correspond well to histological findings.