A 73-year-old man was referred to our hospital to undergo polypectomy. Colonoscopy
showed a protruding polyp, 25 mm in diameter, at the hepatic flexure. ([Figure 1]
a). The polyp was reddish and showed characteristic mucin at its apex, suggesting secretion
from within the polyp. Magnified chromoendoscopy with 0.4 % indigo carmine dye demonstrated
a type IV pit pattern over the entire polyp surface, suggestive of tubulovillous or
villous adenoma [1]. The polyp was removed en bloc by endoscopic mucosal resection and, interestingly,
a jelly-like substance, similar to the mucin at the polyp apex, was also seen at the
resection site ([Figure 1]
b). Surprisingly, the polyp was diagnosed histologically as a submucosal deeply invasive
cancer arising in a tubulovillous adenoma ([Figure 2]). The invasive cancer consisted mainly of moderately differentiated adenocarcinoma
with mucinous carcinoma in part. A cross-sectional view of the polyp showed that the
invasive cancer was totally covered by tubulovillous adenoma, making it impossible
to diagnose the invasive cancer on the basis of the surface pit pattern [2]
[3]. Interestingly, the mucinous carcinoma was connected to the top and the bottom of
the resected lesion, appearing endoscopically as mucinous and jelly-like before and
after resection. As the vertical margin was positive for cancer, additional surgical
resection was performed with curative intent. No locally residual tumor or lymph node
metastasis was detected in the surgically resected specimens.
Figure 1 Colonoscopy showed a protruding polyp, 25 mm in diameter, at the hepatic flexure.
a The polyp was reddish and showed characteristic mucin at its apex, suggesting its
secretion from within the polyp. b A jelly-like substance, similar to the mucin at the polyp apex, was also seen at
the resection site of this polyp.
Figure 2 Histologically, the polyp was diagnosed as a submucosal deeply invasive cancer arising
in a tubulovillous adenoma.
Acknowledgement
This work was supported in part by the Grant-in-Aid for Cancer Research (18S-2) from
the Ministry of Labour and Welfare.
Endoscopy_UCTN_Code_CCL_1AD_2AC
