Clinicopathological and Prognostic Evaluations of Mixed Adenoneuroendocrine Carcinoma of the Colon and Rectum: A Case-Matched Study.

BACKGROUND

Mixed adenoneuroendocrine carcinoma of the colon and rectum is a very rare type of tumor.

OBJECTIVE

The aim of the present study was to evaluate the clinicopathological characteristics and prognosis of mixed adenoneuroendocrine carcinomas of the colon and rectum.

DESIGN

This was a retrospective case-matched analysis (from March 2007 to December 2013).

SETTINGS

This study was conducted at Yokosuka Kyosai Hospital.

PATIENTS

One thousand three hundred six consecutive patients with a preoperative diagnosis of colorectal cancer and who underwent tumor resection were enrolled in the present study. Each patient diagnosed with mixed adenoneuroendocrine carcinoma was 1:2 matched with 2 counterparts who had been diagnosed with adenocarcinoma.

INTERVENTION

Immunohistochemical staining for neuroendocrine markers (chromogranin A, synaptophysin, and CD56) was performed. Cases in which the neuroendocrine component accounted for >30% of the tumor were diagnosed as mixed adenoneuroendocrine carcinomas.

RESULTS

Among 1306 patients, 42 patients (3.2%) were diagnosed with mixed adenoneuroendocrine carcinoma and were compared with 84 patients with adenocarcinoma who had been randomly case matched. The average Ki-67-labeling index value was 78.0% (range, 30.0%-99.0%). Chromogranin A, synaptophysin, and CD56 positivity were observed in 42.9% (18/42), 81.0% (34/42), and 33.3% (14/42) of the tumors. Both the disease-free survival and overall survival were significantly worse for mixed adenoneuroendocrine carcinoma than for adenocarcinoma. Ten patients underwent treatment with oxaliplatin-based chemotherapy. The response rate was 40.0%; the median progression-free survival and overall survival were 6.3 months and 18.1 months.

LIMITATIONS

This was a retrospective single-institution study that included a limited number of cases. The treatment regimens used included different types of oxaliplatin-based chemotherapy.

CONCLUSION

Mixed adenoneuroendocrine carcinoma of the colon and rectum has a poor prognosis after curative resection and should be distinguished from adenocarcinoma.