Diminutive submucosally invasive cancers of the colon and rectum

Only a few cases of submucosally invasive colorectal cancer (SM-CRC) in diminutive colorectal polyps of ≤ 5 mm have been described [1], and as yet there is no detailed knowledge of these cancers.

Pathological SM-CRCs were selected from our colonoscopy database. We examined the frequency of these lesions relative to all colonoscopy examinations and to colorectal neoplasms ≤ 5 mm. The growth type of the lesions was divided into two categories: polypoid growth and non-polypoid growth [2].

A total of 32 692 colonoscopies were performed between September 2002 and December 2012, from which 5690 colorectal neoplasms were detected and treated. Only seven cases of SM-CRC occurred in lesions ≤ 5 mm, accounting for only 0.5 % (7/1358) of colorectal neoplasms ≤ 5 mm.

Baseline patient information, endoscopic and pathological findings, and outcomes are summarized in [Table 1]. Four cases were of protruded type and three cases were of depressed type. All the protruded-type lesions were initially diagnosed before treatment as being adenomas and were resected endoscopically. All the depressed-type lesions were diagnosed before treatment as being malignant. Endoscopic treatment was indicated for six of the patients (#1 – #6), and additional surgery was performed for two patients (#1 and #2) because of histological findings that suggested a high metastatic risk. All cases were of pathologically well-differentiated adenocarcinomas of non-polypoid growth type. No lymph node metastasis was evident in the surgically resected cases. The appearances in patients #2 and #3 are shown in [Fig. 1] and [Fig. 2] respectively.

Tab. 1 Baseline patient data, endoscopic and pathological findings, and outcomes of seven patients with diminutive submucosally invasive colorectal cancers.

Patient number sex; age	Tumor location; type; size, mm	Endoscopic diagnosis	Treatment	Pathological diagnosis	Resection margin	Growth type	Invasion depth, μm	ly	v	pN	Metastatic risk	Outcome
1 M; 67	Ascending colon; Ip; 5	Adenoma	Polypectomy then surgery	Adenocarcinoma (tub1)	Negative	Non-polypoid	1750	0	1	0	High	Lost to follow-up
2 M; 85	Transverse colon; Is; 5	Adenoma	EMR then surgery	Adenocarcinoma (tub1)	Negative	Non-polypoid	1750	0	0	0	High	Alive, disease free
3 M; 76	Transverse colon; Is; 5	Adenoma	EMR	Adenocarcinoma (tub1)	Negative	Non-polypoid	300	0	0	N/A	Low	Alive, disease free
4 F; 86	Rectosigmoid; Is; 4	Adenoma	EMR	Adenocarcinoma (tub1)	Negative	Non-polypoid	1370	0	0	N/A	High	Alive, disease free
5 M; 57	Sigmoid colon; IIc; 5	Intramucosal cancer	EMR	Adenocarcinoma (tub1)	Negative	Non-polypoid	250	0	0	N/A	Low	Alive, disease free
6 M; 53	Sigmoid colon; IIc; 5	Intramucosal cancer	EMR	Adenocarcinoma (tub1)	Negative	Non-polypoid	200	0	0	N/A	Low	Alive, disease free
7 F; 61	Sigmoid colon; IIa + IIc; 5	Submucosal invasive cancer	Surgery	Adenocarcinoma (tub1)	N/A	Non-polypoid	3500	1	0	0	High	Alive, disease free

ly, lymphatic permeation; v, vascular permeation; pN, pathological lymph node metastasis; M, male; F, female; tub1, well-differentiated tubular adenocarcinoma; EMR, endoscopic mucosal resection; N/A, not applicable.

Fig. 1 Images from patient #2. a Conventional colonoscopy showing a protruded lesion (5 mm in diameter) in the transverse colon. b Chromoendoscopy obtained using an indigo carmine spray showing an indistinct depressed area surrounding a protrusion. c Pathology of the specimen from endoscopic mucosal resection (EMR) showing submucosal invasive cancer (1750 µm) of non-polypoid growth type.

Fig. 2 Images from patient #3. a Conventional colonoscopy showing a protruded lesion (5 mm in diameter) in the transverse colon. b Chromoendoscopy obtained using an indigo carmine spray showing an indistinct depressed area surrounding a protrusion. c Pathology of the specimen from endoscopic mucosal resection (EMR) showing submucosally invasive cancer (300 μm) of non-polypoid growth type.

The most important finding of the present study was that all diminutive SM-CRCs were pathologically diagnosed as being of non-polypoid growth type. Shimoda et al. [2] reported that colorectal cancers showing non-polypoid growth tended to invade the submucosa when of a smaller size than those showing polypoid growth. Chromoendoscopy, magnified endoscopy, and image-enhanced endoscopy have been shown to be effective for the precise diagnosis of invasion depth in colorectal cancers [3] [4]. Careful endoscopic observation is strongly recommended when adopting the policies of the DISCARD trial [5] [6].

Endoscopy_UCTN_Code_CCL_1AD_2AB

Competing interests: None

• References

• 1 Kudo SE, Takemura O, Ohtsuka K. Flat and depressed types of early colorectal cancers: from East to West. Gastrointest Endosc Clin N Am 2008; 18: 581-593
• 2 Shimoda T, Ikegami M, Fujisaki J et al. Early colorectal carcinoma with special reference to its development de novo. Cancer 1989; 64: 1138-1146
• 3 Matsuda T, Fujii T, Saito Y et al. Efficacy of the invasive/non-invasive pattern by magnifying chromoendoscopy to estimate the depth of invasion of early colorectal neoplasms. Am J Gastroenterol 2008; 103: 2700-2706
• 4 Ikematsu H, Matsuda T, Emura F et al. Efficacy of capillary pattern type IIIA/IIIB by magnifying narrow band imaging for estimating depth of invasion of early colorectal neoplasms. BMC Gastroenterol 2010; 10: 33
• 5 Ignjatovic A, East JE, Suzuki N et al. Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study. Lancet Oncol 2009; 10: 1171-1178
• 6 Rex DK, Kahi C, O’Brien M et al. The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps. Gastrointest Endosc 2011; 73: 419-422