Pleomorphic lobular carcinoma of the breast: its cell kinetics, expression of oncogenes and tumour suppressor genes compared with invasive ductal carcinomas and classical infiltrating lobular carcinomas

Aims: The study addresses whether pleomorphic lobular breast carcinomas represent a distinct entity with respect to proliferation and apoptosis as well the expression of the p53, bcl-2 and Her2 protein. Methods and results: The study included 30 cases of pleomorphic lobular carcinoma (PLC: G2 n=15, G3 n=15). Poorly differentiated invasive ductal carcinomas (IDC: n=15) and well-differentiated infiltrating lobular carcinomas (ILC: n=15) were used as controls. Lymph node metastases were present equally in all groups. MIB-1 labelling was counted as: PLC (G2) 8.36%: PLC (G3) 11.3%; IDC 44.26%; ILC 2.19% (P=0.0001, P=0.004, P=0.001). Apoptotic index was: PLC (G2) 0.82%: PLC (G3) 1.2% IDC 2.09%; ILC 0.6% (P=0.009, P=0.001). Over-expression of Her2 protein was detected in 53% of PLC (G3) tumours and was present only in scattered cases in the other groups. PLCs and ILCs were strongly positive for bcl-2 and for hormone receptors. while p53+ cells were rare. IDCs exhibited a heterogeneous staining pattern for bcl-2 and for hormone receptors, while p53+ cells occurred considerably more frequently. Stage could not be linked directly to proliferation or apoptosis. Conclusion Our data suggest that more frequent overexpression of Her2 among PLCs (G3) as well as the generally low apoptosis can contribute to their aggressive behaviour.