# The misunderstanding of the R Classification—a survey amongst medical specialties treating breast cancer

## TL;DR

A survey reveals that medical specialists treating breast cancer have differing interpretations of the R Classification, leading to calls for better education and a new classification to avoid confusion.

## Contribution

The study identifies significant misinterpretations of the R Classification across medical specialties and proposes a new Resection margin (Rm) Classification to improve clarity.

## Key findings

- The R Classification is not fully understood or consistently interpreted across medical specialties.
- A Resection margin (Rm) Classification is suggested to differentiate from the current R Classification.
- Multidisciplinary education is recommended to ensure correct application of the R Classification.

## Abstract

Frequent discussions in the tumour board about the Residual tumour (R) Classification of the UICC’s “TNM Classification of Malignant Tumours”, especially in the case of breast surgery specimens, raised the question about differing interpretations amongst different medical specialties. Thus, we designed a survey about the R Classification with a special focus on breast cancer specimens. An online survey was conducted, where a web link to the survey was distributed via email to various medical professional societies dealing with breast cancer in Austria and Germany with the request to distribute the link to their members. The study population consisted of physicians of all educational levels of different medical professions, who deal with breast carcinomas in their daily routine. Two hundred two participants, of which 160 (79.2%) have more than 10 years’ professional experience, took part in the survey; 88 (43.6%) were surgeons/gynaecologists, 80 (39.6%) pathologists, 19 (9.4%) radiation oncologists/ therapists, 8 (4.0%) radiologists, and 7 (3.5%) oncologists. We show that the R Classification is not completely mastered by anyone and that there are significant differences in the interpretation of the R Classification between different medical specialties. For better differentiation between the residual tumour (R Classification) of the TNM and a pure resection margin assessment, we suggest the use of a Resection margin (Rm) Classification to avoid further misunderstandings. To assist better multidisciplinary cooperation and to ensure better patient care all medical disciplines should be educated about the actual meaning and correct application of the R Classification.

The online version contains supplementary material available at 10.1007/s00428-024-03876-8.