Heterotopic gastric mucosa of the rectum--characterization of endocrine and mucin-producing cells by immunocytochemistry and lectin histochemistry. Report of a case.

Heterotopic gastric mucosa in the rectum is particularly uncommon; only 23 cases have been reported to date. Moreover, no studies have been done on the neuroendocrine apparatus and glycoprotein production of the heterotopic mucosa. This study reports on a 13-year-old boy, admitted with rectal bleeding and persistent tenesmus. An ulcerative lesion was found on colonoscopy; biopsies revealed a fundic-type gastric tissue. Medical therapy (H2-blockers) promptly healed the rectal ulcer; surgical excision of the heterotopia was performed with complete and permanent relief of symptoms (3-year follow-up). Immunocytochemistry (PAP) revealed 5-Ht and somatostatin cells in the gastric-type mucosa, as in the normal human stomach. These cells also were present in the surrounding rectal epithelium where PYY-enteroglucagon cells were detected, which were absent in the heterotopic tissue. Mucin histochemistry showed PAS-positive cells also strongly stained by LA lectin in the heterotopic tissue, differentiating the rectal epithelium that remained unstained. Therefore, the morphofunctional status (endocrine cells and mucins) of the gastric heterotopia was almost identical to its orthotopic counterpart, confirming the hypothesis that endocrine cells and mucin-producing cells differentiate their metabolic products according to the anatomic and functional activity of the epithelium where they grow.