Adenocarcinoma of the Rectum-A Composite of Three Different Subtypes With Varying Outcomes?

Abstract

Introduction: Adenocarcinoma of the rectum has been classified by the World Health Organization into various histologic subtypes. We analyzed the effect of the histologic subtype (classic, signet ring cell, and mucinous) on the clinical outcomes of patients with rectal cancer. We hypothesized that clinicopathologic outcome measures such as tumor margins, tumor regression grade, recurrence rate, and survival would vary with the histologic subtype.

Materials and methods: We conducted a retrospective analysis of a prospectively maintained database. All patients with stage I-III rectal adenocarcinoma were included.

Results: From May 2010 to August 2013, 273 patients underwent curative resection. Both mucin-secreting variants were more common in younger patients and presented at a more advanced stage. Also, 54% and 48% of those with signet ring cell carcinoma (SRCC) and mucinous adenocarcinoma (MAC) had node-positive disease compared with the rate in the classic variant (30%). Circumferential resection margin positivity was 24% with MAC and 19% with SRCC compared with 4% with the classic variant. Disease-free survival for those with the classic and mucinous variants was 38.5 and 37.4 months, respectively. In contrast, it was 28.6 months in the SRCC group. The overall survival did not differ significantly.

Conclusion: Rectal adenocarcinoma presents as a spectrum of disease, with progressively worsening outcomes from classic to MAC to SRCC. These aggressive variants might warrant more aggressive resection. These data from the Indian subcontinent differ from the published data from Western countries.

Keywords: Histopathological subtypes; Mucinous adenocarcinoma; Rectal cancer; Signet ring cell carcinoma; Survival outcomes.