Pathologic diagnosis

The macroscopic shapes of lesions were classified into three groups: elevated, flat and depressed (17). Rectal tissues were fixed in formalin and embedded in paraffin, and 5-µm consecutive sections were obtained for hematoxylin-eosin staining. According to the WHO diagnostic criteria, HGIN was diagnosed if highly heterotypic glands confined to the lamina propria and the epithelial layer were present, but evidence for ISM was not observed (8). If the tumor had invaded submucosa through the mucosal myometrium, invasive carcinoma was diagnosed. The diagnostic criteria for ISM were as follows: longitudinal stripe-like, mass-like, or focal eosinophilic smooth muscle fibers mixed with heterotypic glands or arranged around the heterotypic glands (Figure 1).

The same case with microphotograph shows the following: (A,B) adenoma with high-grade intraepithelial neoplasia (HGIN) using endoscopic forceps biopsy (EFB); (C,D) moderately differentiated adenocarcinoma using TRUS-guided CNB; (E,F) moderately differentiated adenocarcinoma with partly mucinous adenocarcinoma, and tumor cell infiltration into the deep muscular layer of the intestine with postoperative pathology (A,C,E) low-power view (HE staining, ×4); (B,D,F) high-power view (HE staining, ×20). TRUS, transrectal ultrasound; CNB, core needle biopsy.