Fig. 4: Repertoire of genetic alterations in primary and metastatic metaplastic breast cancers.

a Representative photomicrographs of a H&E-stained primary metaplastic breast cancer (pMETA) with predominant chondroid differentiation (top), and of a metastatic metaplastic breast cancer (mMETA) with predominant squamous differentiation involving lung (bottom). Scale bars, 100 μm. b Boxplots depicting the non-synonymous mutation burden of metastatic metaplastic BCs (mMETA; n = 6), metastatic invasive ductal carcinomas of no special type (mIDC-NSTs; n = 18) matched by age, menopausal status, and estrogen receptor (ER)/HER2 status, and primary metaplastic BCs (pMETA; n = 5). Mann–Whitney U test, two-tailed. c Comparison of the cancer genes most frequently affected by non-synonymous somatic mutations, amplifications, or homozygous deletions in mMETA (n = 6), age, menopausal status, and ER/HER2 receptor status-matched metastatic invasive ductal carcinomas of no special type (mIDC-NSTs; n = 18), and primary metaplastic BCs (pMETA; n = 5). Cases are shown in columns and genes in rows. Genetic alterations are color-coded according to the legend. ER/HER2 status and predominant histologic component are shown on phenobars (top). No significant different mutation frequencies were found using Fisher’s exact test. Indel insertion/deletion, LOH loss of heterozygosity, SNV single nucleotide variant.