Distal spread of low and middle rectal cancer in mesorectum and rectal wall found by large slices stained with CK20

Abstract

Objective To examine the frequency and mode of distal spread of low and middle rectal cancer in the mesorectum and rectal wall. Methods Thirty-four specimens from low and middle rectal cancer were collected between August 2004 and December 2005 in Cancer Center of Sun Yat-sen University. Twenty-eight specimens of low and middle rectal cancer were collected between October 2006 and October 2007 in Shandong Provincial Hospital of Shandong University. All 62 specimens were studied using large slices stained with CK20. Logistic regression was used to analyze clinicopathologic factors related to distal spread of low and middle rectal cancer in the mesorectum and rectal wall. Results Two types of distal spread of the tumor were observed in rectal wall: submucosa invasion and muscularis propria invasion. Distal spread in rectal wall was observed in 16% (10/62) of the patients. The length of distal spread in rectal wall was found from O. 5 cm to 1.0 cm. Four types of distal spread of the tumor were observed in mesorectum: lymph node invasion, blood and lymphatic vessel invasion, perineural invasion, isolated neoplastic microfoci. Distal spread in mesorectum was observed in 24% (15/62) of the patients. The length of distal spread in mesorectum was found from 0. 5 cm to 4. 0 cm. Three more cases with microcapillary invasion in distal mesorectum was observed by immunohistochemical technique, which was difficult to identify by conventional HE staining. Univariate analysis showed that serum CEA , lymph node invasion, CMI and TNM stage were correlated with distal spread of low and middle rectal cancer in the mesorectum and rectal wall. TNM stage was shown to be independent impact factor by multivariate analysis( Wald = 9. 567, P =0. 002). Conclusion TNM stage is an independent impact factor for distal spread of low and middle rectal cancer in the mesorectum and rectal wall. Resection of 1.5 cm for distal rectal wall is necessary for a curative intention, but it must be emphasized that the clearance for distal mesorectum should be 5 cm at least. Key words: Rectal neoplasms ; Neoplasm metastasis; Mesentery; Keratin-20