I read with great interest the article by Houssami et al.1 In a large retrospective series including 4035 core needle breast biopsy samples, the authors estimated (among others) B3 underestimation rates (the proportion of lesions diagnosed as atypical ductal hyperplasia [ADH], lobular carcinoma in situ [LCIS], or radial scar on core needle biopsy being upgraded to cancer after open biopsy was performed). Compared with the literature, the reported B3 underestimation rate of 44% was rather high. In a literature overview including 23 articles, only 4 reported higher B3 underestimation rates. In all these studies, core needle biopsy was performed with a 14-gauge needle, and no vacuum-assisted biopsy was performed for tissue sampling. In the study by Houssami et al., approximately two-thirds of the lesions were sampled using vaccuum-assisted biopsy.
The authors propose several reasons for underestimating malignancy by core needle biopsy, including inaccurate targeting of the lesion, partial sampling, and small tissue volume. In addition, they mention that interpretation factors may influence underestimation rates, stating that pathologists who are more prone to use B3 (for ADH, LCIS, etc) for benign lesions would have lower underestimation rates than pathologists who use B3 strictly according to defined criteria.
I believe that the study by Houssami et al. suggests the opposite, namely that pathologists are becoming more prone to use B3 for malignant lesions. Before the era of percutaneous breast biopsies, a B3 diagnosis entailed follow-up that was completely different from that for a malignant diagnosis (ie, no further treatment vs complete breast cancer treatment). With the advent of core needle breast biopsy, a B3 diagnosis results in the exact same follow-up as a diagnosis of ductal carcinoma in situ (ie, excision). Therefore, in case of doubt, pathologists may be less tempted to give a malignant diagnosis, especially based on small tissue samples. They know that, in the case of malignancy, a ‘softer’ B3 diagnosis would lead to the correct diagnosis in any case.
The study of Houssami et al., which extended over a 9-year period, provides the unique opportunity to confirm whether B3 underestimation rates have increased over the years and whether a shift toward a less aggressive diagnosis may be taking place.