Microglandular adenosis: a prime suspect in triple‐negative breast cancer development

Microglandular adenosis ( MGA ) and atypical MGA ( AMGA ) are unusual lesions of the breast. They were once regarded as benign proliferative lesions and innocent bystanders. Several lines of evidence suggested that they could be neoplastic, clonal lesions and a non‐obligate precursor for triple‐negative breast cancers ( TNBC ). Recent work published in The Journal of Pathology by Guerini‐Rocco and colleagues provided further evidence regarding the precursor–product relationship between MGA / AMGA and TNBC . Using a massively parallel sequencing approach, they demonstrated that MGA / AMGA , particularly those associated with TNBC , could be clonal neoplastic lesions showing clonal non‐synonymous mutations, but none in pure MGA . Importantly, those alterations were observed in the associated TNBC . They were also able to identify recurrent alterations in TP53 in those MGA / AMGA cases as well as their associated TNBC . The findings, in conjunction with others, underscore the significance for MGA in clinical diagnosis. The potential of a benign lesion to progress into an aggressive malignant tumour implies that modification of the current management approach may be necessary. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.