1. Clinicopathologic Analysis of Rectal Carcinoids Reported in Japan

Abstract

The cases of rectal carcinoid reported in Japan have shown a significant increase in recent years, and total numbers of cases recorded in the literature until 1976 were 65. Average age of the patients was 48 years, and the overall percentages were 61% in males and 39% in females. The primary tumors were usually found 4 to 6 cm above the anal ring as a single submucosal nodule with yellowish color, but there was no constant laterality in their localization. The majority of the tumors were below 2 cm in diameter, and the simple local excision was performed. The cases reported had nonspecific rectal symptoms of bleeding and pain, and only two cases were accompanied by carcinoid syndrome. The metastasis into local lymph nodes or liver was observed in 11 cases including one with a primary tumor below 2 cm in diameter. The rectal carcinoids regardless of their size proliferated in lamina propria mucosae, and often invaded submucosa beyond muscularis mucosae. The muscular invasion and lymph node metastasis were more pronounced in the cases with the lesion more 2 cm, in whom the radical operation including an abdominoperineal excision of rectum was undertaken as adequate therapy.A primary carcinoid tumor of rectum can be correctly diagnosed by characteristic histologic patterns such as the formation of ribbon or rosette and sclerosing pattern compres-sed by dense connective stroma. It was found that the rectal carcinoid belongs to the family of slightly argyrophilic carcinoid by Grimelius' silver nitrate stain. In all of the cases examined by electron microscope, neoplastic cells contained abundant round secretory granules measuring 200 nm on average in diameter.