Patterns of neoplastic foci and lymph node micrometastasis within the mesorectum

Background and aims: Local recurrence after rectal cancer surgery is conceived to result from microscopically incomplete resection. We aimed to investigate the patterns of mesorectal neoplastic foci, and examined the involvement and micrometastasis of lymph nodes. Methods: Observation of large tissue slice and analysis of tissue microarray were integrated in the pathological study of 31 total mesorectal excision (TME) specimens. Results: Altogether, 349 mesorectal neoplastic foci were examined from 18 specimens. Almost 33% of them were in the outer layer of mesorectum. Concerning position of primary tumor, ipsilateral neoplastic foci were significantly more than contralateral neoplastic foci. Distal mesorectal spread was found in four patients with the distance ranging from 1 to 3.5 cm. Four specimens were diagnosed to have circumferential margin involved. Nine hundred seventy-two lymph nodes were harvested with 128 involved by tumor. No significant difference in occurrence of micrometastasis was observed among tumors of different stage. Conclusions: Combination of large tissue slice and tissue microarray provided a more detailed method in studying the metastasis of rectal cancer. Complete excision of the mesorectum with fascia propria circumferentially intact is essential. Circumferential margin involvement and micrometastasis suggested that tumor spread may go beyond the scope of a single TME procedure.