Poorly Differentiated Variants of Colorectal Carcinoma; Is There a Survival Difference Between WHO-listed Subtypes? A Single Teaching Institute Experience

Document Type

Conference Proceeding

Publication Date

3-1-2024

Publication Title

Lab Invest

Abstract

Background: Undifferentiated colon carcinoma (UC) is a rare histologic variant of colorectal adenocarcinoma (CRC). The WHO morphologic criteria are not very well-defined and there is some morphologic overlap with other poorly differentiated variants of CRC, including adenocarcinoma NOS in the absence of conventional morphology (PDA-NOS), medullary carcinoma (MC), large cell neuroendocrine carcinoma (LNEC) and lymphoepithelioma-like carcinoma (LELC). This study aims to see if there is a survival difference between UC and other poorly differentiated variants of CRC, as well as clinicopathological features that may affect prognosis. Design: All consecutive patients with the diagnoses of PDA-NOS, MC, LNEC, UC and LELC between July, 2018 and July, 2023 were included. H&E slides were retrieved and reviewed by two gastrointestinal pathologists. Relevant clinical and histologic parameters were recorded. Cox proportional-hazards model was used for multivariate analysis, while log-rank test and Kaplan- Meier were used for univariate and survival analyses. Results: A total of 77 patients were included. Median age was 75 (41-97). Median follow up period was 13 months (1-84). There were 63 PDA-NOS, 3 LNEC patients, 6 MC patients, 4 UC and 1 LELC patients. Among the PDA-NOS patients, 20 (32%) cases showed focal features with conventional morphology. Twenty-five (40%) out of 63 PDA-NOS, all 3 (100%) LNEC, 2 (33.3%) out of 6 MC and 2 (50%) out of 4 UC patients died during the follow-up period. 1 patient with LELC is alive and doing well. Features included in multivariate analysis were cancer subtype, size, gender, laterality, perforation, extramural large vessel invasion, TNM and MMR(IHC). Multivariate analysis showed tumor size (TS) (P=0.04) and T stage (P=0.04) were associated with poor prognosis. Log-rank test showed cancer subtype (P=0.04), TS (P=0.004), T (P=0.04) and M (P=0.001) stages to be of statistical significance. No survival difference was found between PDA-NOS (both conventional and unconventional morphology) and UC (P=0.84). Among all the cancer subtypes, LNEC has dismal prognosis and MC has better prognosis compared to other subtypes (P=0.04) (figures 1 & 2). Conclusions: Poorly differentiated CRC are associated with poor prognosis, as 32 (41%) out of 77 patients died during the follow up period. In our cohort, no survival difference was found between PDA-NOS and UC. This raises questions about the prognostic significance of this category or highlights that more clearly defined criteria are necessary.

Volume

104

Issue

3

First Page

S853

Last Page

S854

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