Lateral Pelvic Sidewall Nodes

Abstract

CASE SUMMARY: A 68-year-old woman presented with rectal bleeding, urgency, and tenesmus. A digital rectal examination confirmed a craggy mass infiltrating into the sphincter complex. Follow-up colonoscopy noted a low-rectal tumor (3 cm from the dentate), and histopathology confirmed a moderately differentiated adenocarcinoma. Subsequent staging with MRI confirmed a 5-cm circumferential low-rectal neoplasm with extramural vascular invasion and threatened circumferential resection margin. The neoplasm abutted the posterior vaginal wall and was invading the internal sphincter complex. Four enlarged mesorectal nodes (>7 mm) and several enlarged right pelvic sidewall nodes (largest at 17 mm) were also observed. There was no evidence of distant disease. The patient underwent long-course neoadjuvant chemoradiotherapy. Restaging showed a good treatment response with some regression and no involvement/encroachment of the vagina. All the mesorectal nodes had reduced in size (~4 mm), and all but one of the right pelvic sidewall nodes had also decreased in size. However, 1 pelvic sidewall node (obturator fossa) still remained at 10 mm. After the tumor board discussion, a decision to proceed to abdominoperineal resection with right sidewall clearance was made. Final histopathology confirmed a moderately differentiated adenocarcinoma with no mesorectal nodal involvement (19 nodes sampled), and 1 of 7 sidewall nodes had evidence of metastatic adenocarcinoma.