Lower-risk histologies are less common and include low-grade adenosquamous and fibromatosis-like MpBCs.11 The majority of MpBCs lack estrogen receptor (ER), progesterone receptor (PR), and erb-b2 receptor tyrosine kinase 2 (ERBB2) expression.12,13 Several studies have examined the molecular features of this group, noting diversity in gene-expression profiling, a high frequency of acquired, somatic TP53 variants, and alterations affecting the PI3K-AKT1-MTOR pathway, including PIK3CA and PTEN variants.4,14,15,16,17. Here, ERBB2 is linked to fibromatosis.