Clinicopathologic Features of Untreated Colorectal Cancer with Acellular Mucin-Only Lymph Nodes

Area of Science:

• Oncology
• Pathology
• Cancer Research

Background:

• Lymph nodes (LNs) with acellular mucin are considered metastasis-negative in treated colorectal cancers (CRCs).
• Data on staging these LNs in untreated CRCs are lacking.
• Standardizing staging for these specific cases is crucial for accurate prognosis.

Purpose of the Study:

• To determine the appropriate pathological staging (pN stage) for lymph nodes containing only acellular mucin in untreated colorectal cancers.
• To analyze the clinicopathological features and survival outcomes of untreated CRC patients with such lymph node findings.
• To compare these outcomes with established pN0 and pN1 control groups.

Main Methods:

• Retrospective analysis of 63 untreated CRC cases with acellular mucin-containing LNs from US institutions and 23 from the Dutch Nationwide Pathology Databank.
• Evaluation of pathologist practice patterns in staging and additional studies.
• Comparison of survival data between the study group and control groups (102 pN0 and 76 pN1 untreated CRC cases).

Main Results:

• Pathologist practices were consistent across US and Dutch institutions.
• Tumors in the study group were more frequently right-sided, mucinous, and mismatch repair deficient.
• The study group exhibited significantly lower rates of lymphovascular invasion, local recurrence, and distant metastasis compared to the pN1 group.
• No CRC-related deaths occurred in the study group, mirroring the pN0 group, unlike the pN1 group.

Conclusions:

• Lymph nodes containing only acellular mucin in untreated colorectal cancer should be classified as pN0.
• This classification is consistent with the management of neoadjuvant-treated CRCs.
• Staging these LNs as pN0 reflects a favorable prognosis, similar to pN0 cases.