PTEN and triple-negative breast carcinoma: While this cancer subtype is characterized by absence of estrogen and progesterone receptors as well as HER2 over-expression, triple negative breast cancer samples appear to constitute a heterogeneous group as mutations in TP53, PIK3CA, and PTEN have recently been shown to confer cancer driving properties in most but not all cases (Curtis et al., 2012; Shah et al., 2012).