Histopathological Complexities and Diagnostic Challenges in Familial Adenomatous Polyposis: A Case Report.

Familial adenomatous polyposis (FAP) is a rare inherited disorder characterized by numerous adenomatous polyps throughout the colon and rectum, leading to a significantly increased risk of colorectal cancer. We present the case of a 19-year-old male patient with a known family history of FAP who presented with recurrent lower abdominal pain, altered bowel habits, and rectal bleeding. Initial examination identified rectal polyps, and subsequent colonoscopy revealed multiple adenomatous polyps. Histopathological analysis initially raised the possibility of oxyntic adenomas due to the glandular tissue's anastomosing and cribriform pattern. However, further detailed evaluation, which identified a significant population of both chief and parietal cells within the glandular pits, supported the diagnosis of mixed hyperplastic/fundic gland polyps with focal low-grade dysplasia. This case highlights the diagnostic complexities in distinguishing between oxyntic adenomas and mixed hyperplastic/fundic gland polyps in FAP patients, emphasizing the importance of accurate diagnosis in guiding management, including surveillance, surgical intervention, genetic counseling, and lifestyle modifications.