Do Acellular Mucin Pools in Resection Margins for Rectal Cancer Influence Outcomes?

Positive resection margins predict poor prognosis in rectal cancer (RC). Literature on the impact of acellular mucin (ACM) in circumferential resection margin (CRM) or distal resection margin (DRM) of proctectomy specimens on RC recurrence and outcomes is lacking. The retrospective study was conducted to determine the oncological outcomes of the RC patients with ACM in or within 1 mm of margins of the rectal resection specimens. Histopathology reports of RC resection specimens dated from June 2013 till May 2016 were reviewed to identify cases with ACM in CRM (n = 10) and DRM (n = 2). Relevant details of these patients were gathered from the electronic medical record. Pattern of recurrence was studied. In cases with only ACM in CRM (n = 10), disease (primary tumor or nodes) was radiologically reaching the mesorectal fascia except two, who had extra mesorectal nodes. Median distance of tumor from anal verge was 2 cm. All patient received neoadjuvant therapy: four patients received chemoradiotherapy (NACTRT), one received short-course radiotherapy, and five received NACTRT followed by neoadjuvant chemotherapy. Abdominoperineal resection, intersphincteric resection and total pelvic exenteration were done for six, three, and one patient, respectively. In two additional cases of anterior resection with ACM in DRM, one underwent upfront resection while the other received NACTRT. Over a mean follow-up period of 43 months, four patients developed recurrences. Two of them had local recurrence and only one had isolated local recurrence. ACM in resection margins of RC resection specimens does not seem to increase likelihood of local recurrence.