Answer: Peutz-Jeghers polyp with pseudoinvasion

Histology: The patient underwent a small bowel resection, which revealed multiple cytologically benign polyps with arborizing musculature, characteristic of the Peutz-Jeghers Polyp. These polyps typically undergo herniation of cystically dilated epithelium into the bowel wall, and these may extend to the serosa and form tumor masses as in the current case. This is analogous to Colitis Cystica Profunda. Importantly, the herniated mucosa is cytologically benign, and carries with it its lamina propria.

Discussion: The epithelium lacks the nuclear stratification, hyperchromasia, and increased nucleus-to-cytoplasm ratio of adenomatous polyps. The lack of significant atypia and malignant cells floating within mucin dismisses the possibility of mucinous carcinoma. Similarly, the presence of a benign lamina propria and benign cytology dismisses the possibility of a metastatic adenocarcinoma to the small bowel.