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invasive micropapillary carcinoma ( impc ) was first identified as a variant of invasive breast cancer by siriaunkgul and tavassoli 1 .
recently , impc has been reported in association with other tissues , including the urinary bladder , lung , ovary , salivary gland , stomach and colon 2 .
impc has clinical characteristic carcinoma findings , with a high incidence of lymphatic involvement , lymph node metastases , and a poor clinical outcome , and has histological features consisting of round - to - oval micropapillary clusters surrounded by clear spaces and a lack of fibrovascular cores .
impc has an inside - outside growth pattern with reversed polarity , where the stromal - facing surfaces of the tumor cells acquire apical secretory properties , as demonstrated by muc1 or ema immunohistochemical staining on the surface . in the case of colorectal impc , few descriptions of endoscopic observation via magnifying colonoscopy and endoscopic mucosal resection exist in the literature .
pit pattern classification of colorectal lesions determined by magnifying endoscopy has been reported to be related to the histologic characteristics of the lesions 3 ; therefore , this modality is effective for invasion depth diagnosis and treatment selection .
additionally , given that the irregular microvessels of the lesion are analyzed with respect to the heterogeneity of their diameter and/or distribution using narrow band imaging ( nbi ) magnification , it is possible to discriminate between adenoma versus carcinoma , and to determine the depth of invasion 4 .
herein we report a case of colon impc that underwent colonoscopic observation and endoscopic mucosal resection .
a 47-year - old woman visited our hospital as follow - up for a positive fecal occult blood test .
blood tests only revealed the existence of mild anemia ( hemoglobin , 10.7  g / dl ) ; serum levels of carcinoembryonic antigen ( cea ) and ca19 - 9 were normal .  
colonoscopy was performed using a magnifying colonoscope ( pcf - q260azi , olympus , tokyo , japan ) .
white light colonoscopy revealed a semi - pedunculated reddish polyp <  10  mm in diameter with a gently irregular surface , but without ulceration or erosion , as well as mild tension in the sigmoid colon (  fig.1 ) . 
 a white light colonoscopic examination of the sigmoid colon revealed a semi - pedunculated reddish polyp <  10  mm in diameter with a gently irregular surface , but without ulceration or erosions .
magnifying nbi colonoscopy showed an irregular surface pattern with heterogeneity in the vascular diameter and a sparse vascular distribution , suggestive of stromal invasion of tumor cells (  fig .  2 ) .
magnifying endoscopy using crystal violet staining revealed pits with irregular margins , unclear contours , and narrowed lumens , and decreased / disappearing stainability in the stromal area .
in addition , the stromal area between each duct was dilated ( fig .  3 ) .
the preoperative diagnosis was early - stage sigmoid colon cancer with submucosal invasion , and diagnostic endoscopic resection of the sigmoid colon tumor was performed because the patient strongly hoped for endoscopic resection due to the small size of the lesion . 
 magnifying nbi colonoscopy findings .
a global image is shown in a , and an extended image of the area in the box is shown in b. this polypoid lesion had an irregular surface pattern and heterogeneity in both vascular diameter and distribution .
the vascular distribution was also sparse . 
 magnifying colonoscopic findings using crystal violet staining .
a global image is shown in a , and an extended image of the area in the box is shown in b. the polypoid lesion had irregular margins , unclear contours , and narrow pit lumens , and the crystal violet stainability in the stromal area was diminished and partially disappeared .
microscopically , massive submucosal invasion to a depth up to 3.6  mm with extensive lymphatic invasions was observed ( fig . 
the lesion was predominantly ( ~80  % ) composed of polygonal cells arranged in clusters surrounded by lacunar - like clear spaces ( fig . 
4  b ) , and the remaining 20  % was moderately differentiated tubular adenocarcinoma .
immunohistochemically , muc1 expression was observed at the stromal edges of tumor clusters in the micropapillary structures , thus appearing as an  inside - out staining pattern 2 ( fig . 
.  4  d ) and negative for cytokeratin 7 (  fig . 
histological analysis of the resected specimen showed a massive submucosal invasion to 3.6  mm , with extensive lymphatic invasion .
b this lesion was predominantly composed of polygonal cells arranged in clusters surrounded by lacunar - like clear spaces .
c muc1 expression of tumor cells was found at the stromal edges of tumor clusters in the micropapillary structures , a characteristic  inside - out staining pattern .
these immunohistochemical findings suggested impc of the colon . although the vertical margin of the resected specimen was negative and no regional lymph node swelling or metastasis by chest and abdominal computed tomography ( ct ) were apparent , laparoscopy - assisted sigmoidectomy and regional lymph node resection were performed .
a 47-year - old woman visited our hospital as follow - up for a positive fecal occult blood test .
blood tests only revealed the existence of mild anemia ( hemoglobin , 10.7  g / dl ) ; serum levels of carcinoembryonic antigen ( cea ) and ca19 - 9 were normal .  
colonoscopy was performed using a magnifying colonoscope ( pcf - q260azi , olympus , tokyo , japan ) .
white light colonoscopy revealed a semi - pedunculated reddish polyp <  10  mm in diameter with a gently irregular surface , but without ulceration or erosion , as well as mild tension in the sigmoid colon (  fig.1 ) . 
 a white light colonoscopic examination of the sigmoid colon revealed a semi - pedunculated reddish polyp <  10  mm in diameter with a gently irregular surface , but without ulceration or erosions .
magnifying nbi colonoscopy showed an irregular surface pattern with heterogeneity in the vascular diameter and a sparse vascular distribution , suggestive of stromal invasion of tumor cells (  fig .  2 ) .
magnifying endoscopy using crystal violet staining revealed pits with irregular margins , unclear contours , and narrowed lumens , and decreased / disappearing stainability in the stromal area .
in addition , the stromal area between each duct was dilated ( fig .  3 ) .
the preoperative diagnosis was early - stage sigmoid colon cancer with submucosal invasion , and diagnostic endoscopic resection of the sigmoid colon tumor was performed because the patient strongly hoped for endoscopic resection due to the small size of the lesion . 
 magnifying nbi colonoscopy findings .
a global image is shown in a , and an extended image of the area in the box is shown in b. this polypoid lesion had an irregular surface pattern and heterogeneity in both vascular diameter and distribution .
the vascular distribution was also sparse . 
 magnifying colonoscopic findings using crystal violet staining .
a global image is shown in a , and an extended image of the area in the box is shown in b. the polypoid lesion had irregular margins , unclear contours , and narrow pit lumens , and the crystal violet stainability in the stromal area was diminished and partially disappeared .
microscopically , massive submucosal invasion to a depth up to 3.6  mm with extensive lymphatic invasions was observed ( fig . 
the lesion was predominantly ( ~80  % ) composed of polygonal cells arranged in clusters surrounded by lacunar - like clear spaces ( fig . 
4  b ) , and the remaining 20  % was moderately differentiated tubular adenocarcinoma .
immunohistochemically , muc1 expression was observed at the stromal edges of tumor clusters in the micropapillary structures , thus appearing as an  inside - out staining pattern 2 ( fig . 
.  4  d ) and negative for cytokeratin 7 (  fig . 
histological analysis of the resected specimen showed a massive submucosal invasion to 3.6  mm , with extensive lymphatic invasion .
b this lesion was predominantly composed of polygonal cells arranged in clusters surrounded by lacunar - like clear spaces .
c muc1 expression of tumor cells was found at the stromal edges of tumor clusters in the micropapillary structures , a characteristic  inside - out staining pattern .
these immunohistochemical findings suggested impc of the colon . although the vertical margin of the resected specimen was negative and no regional lymph node swelling or metastasis by chest and abdominal computed tomography ( ct ) were apparent , laparoscopy - assisted sigmoidectomy and regional lymph node resection were performed .
impc was first reported as a variant type of invasive breast cancer by siriaunkgul and tavassoli in 1993 1 .
however , the endoscopic features of and optimal therapeutic management strategies for colon impc have not yet been elucidated .
we recently encountered a case of early - stage colon impc , and performed a minute magnifying colonoscopic observation , including nbi endoscopy and crystal violet chromoendoscopy . in the current report , we have discussed the endoscopic diagnosis and the therapeutic strategy for this case of colon ipmc .
most colon impc cases are identified at an advanced stage ; therefore , surgery and chemotherapy are the primary clinical management strategies .
only 5 cases of colon impc ( including the current case ) have been categorized as t1 ( tnm classification ) tumors ( table  1 ) 5 
 6 
 7 
 8 . in 4 cases including the current one , endoscopic resection was performed 5 
 6 
 8 . however , in all of these cases , submucosal invasion and lymphatic vessel invasion were observed .
additional surgeries were performed in 3 cases , and conservative treatment was selected in the fourth case due to severely complicated disease . in the latter case ,
unfortunately , colonoscopy and ct scans revealed local recurrence and multiple distant metastases in the lung , liver , lymph node , and spleen 6 months after endoscopic resection 6 .
thus , sufficient attention should be paid to colon impc even if the disease is diagnosed at an early clinical stage , because these patients have been reported to experience a worse prognosis than those with non - impc early - stage colon cancer 9 
 10 .
ly , lymphatic invasion ; v , venous invasion ; s , sigmoid colon ; nd , not described ; er , endoscopic resection ; ct , computed tomography in the current case , white light and magnifying colonoscopy using nbi and crystal violet staining were performed .
first , white light colonoscopy revealed a semi - pedunculated reddish polyp with a gently irregular surface and producing mild tension despite its small size , suggestive of submucosal invasion .
magnifying nbi colonoscopy showed an irregular surface pattern with heterogeneity in vascular diameter and distribution , and magnifying endoscopy using crystal violet staining revealed a highly irregular type vi pit pattern 3 .
in addition , the vascular contribution was sparse , and the stromal area between each duct was dilated . based on these endoscopic findings ,
the current case was not considered to be a typical mucosal adenoma or carcinoma , and distinction from an unusual type of carcinoma , such as mucinous or undifferentiated carcinoma with submucosal deep invasion , was required .
impc consists of neoplastic cells without fibrovascular cores that proliferate into the stroma , and the tumor clusters are surrounded by clear spaces .
the present case was 7  mm , which is the smallest colonic impc thus far reported .
we suggest that impc should be considered in the differential diagnosis if colonoscopy suggests a submucosal deep invasion , an irregular pit pattern with a wide stromal area , and an invisible vascular pattern despite a small size
. these may be characteristic features of early - stage colon impc identifiable with magnifying colonoscopy .
however , a future study with a larger number of cases is required to confirm these findings .
the clinical characteristic findings of colon impc include a high incidence of lymphatic involvement and lymph node metastases , as well as a poor clinical outcome .
extensive lymphatic involvement was observed in the current case , despite the very small size of the lesion .
kim et al . showed that metastases to local lymph nodes were observed in 2 out of 3 patients with impc tumors that infiltrated into the submucosal membrane ( pt1 ) 9 .
xu et al . reported that stage i and ii impc patients experience shorter survival compared to non - impc patients 10 . in conclusion , we suggest that cases of colon impc should be diagnosed at the earliest stage possible and should be appropriately treated .
we have found that submucosal deep invasion , an irregular pit pattern with a wide stromal area , and invisible vascular patterns despite a small tumor size are key endoscopic features of colon impc .
background and study aims : we present a case of invasive micropapillary carcinoma ( impc ) of the colon treated by endoscopic resection following magnifying endoscopy . 
 a 47-year - old woman visited our hospital for follow - up of a positive fecal occult blood test . 
 colonoscopy revealed a semi - pedunculated reddish polyp , the surface of which showed gentle irregularity , and mild tension in the sigmoid colon . 
 magnifying colonoscopy with narrow band imaging revealed an irregular surface pattern with heterogeneity in vascular diameter and distribution . 
 magnifying endoscopic findings using crystal violet staining showed an irregular pit pattern with an expansion of stromal areas . 
 endoscopic resection of the sigmoid colon tumor was performed , and the histology of the resected specimen primarily revealed a micropapillary component with a small moderately differentiated adenocarcinoma component that massively invaded into the submucosal layer , accompanied by lymphatic invasion , although the tumor was very small ( 7  mm in diameter , smaller than any in previous reports ) . 
 laparoscopy - assisted sigmoidectomy and regional lymph node resection were performed ; neither cancer nor lymph node metastases were present . 
 this is the first report of a case with early - stage colonic impc observed with magnifying colonoscopy .