Anal-transitional and bronchial metaplasia within the ileostomy of a small bowel allograft: a case report.

Epithelial metaplasia is a phenomenon where a native mucosal cell type is replaced by another due to altered stem cell differentiation, usually as the result of long-standing injury or inflammation. It is common in ileostomies performed with native small bowels for both neoplastic and inflammatory conditions. We present a case of anal-transitional and bronchial epithelial metaplasia that occurred near the ileostomy of a small bowel allograft in a seven-month-old male transplanted for short bowel syndrome related to gastroschisis. The anal-transitional metaplastic mucosa had an immunophenotype (CK7- and p63-positive) similar to that of normal mucosa at the anal transition zone and a DNA STR profile consistent with the donor. To our knowledge, this represents the first report of this type of metaplasia occurring in ileostomies in the English literature. It is important for clinicians and pathologists to recognize these benign mucosal alterations to avoid diagnostic confusion.