Morphological change of a laterally spreading rectal tumor over a short period.

BACKGROUND: Laterally spreading tumors (LSTs) are generally defined as superficial lesions ≥10 mm in diameter that typically extend laterally rather than vertically along the colonic wall. LSTs are usually categorized into 2 subtypes: granular type and nongranular type. Large nodules or depressed areas in granular-type LSTs (LST-Gs) are endoscopic findings of a cancerous component and sometimes represent submucosal invasion. However, the lateral growth and development of LST-Gs remains unclear. CASE PRESENTATION: This case report describes a case of 79-year-old woman who underwent total colonoscopy due to a positive fecal occult blood test and was detected a LST-G, about 30 mm in diameter in the lower rectum. The lesion consisted of not only aggregated small and large nodules typically seen in LST-Gs but also the hardly elevated flat parts. In the flat part, there were dilated round pits and no evident capillary vessels. Three months later, the flat part increased in height, the dilated round pits were partly replaced by type IIIL pits, and capillary vessels were evident. The lesion was removed by endoscopic submucosal dissection, and diagnosed pathologically as tubular adenoma. We performed the sequence analyses on KRAS, BRAF, NRAS and PIK3CA genes in flat part and nodular part separately, and a mutation of KRAS gene at codon 146 was observed at only nodular part, suggesting probable that nodular part be a precancerous lesion. CONCLUSION: This is a unique and suggestive case, providing information on progression of LST-Gs at the very early stage to carcinogenesis.

Bone formation in a rectal inflammatory polyp.

Heterotopic bone formation (osseous metaplasia) is rarely detected in the gastrointestinal tract. Most of reported cases are associated with malignant lesions. We herein report a case of osseous metaplasia in a rectal inflammatory polyp and a review of the literature on suggested mechanisms for its aetiology. A 39-year-old man visited our hospital with a chief complaint of melena. Total colonoscopy revealed a slightly reddish subpedunculated polyp, about 12 mm in diameter, in the lower rectum. Endoscopic resection was performed. Histologically, several foci of heterotopic bone formation were found. From the review of the literature, all of the polyps described were larger than 10mm in diameter, 55.6% showed inflammatory changes, and 62.5% were detected in the rectum. Osteogenic stimulation was considered to be a result of the inflammatory process. As our inflammatory polyp was located in the rectum, the pathogenesis could be a reactive change stimulated by the repeated local trauma, or be on a peculiar characteristic of the rectal mucosa itself.