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 over-expression of Her2 among PLCs (G3) as well as the generally low apoptosis can contribute to their aggressive behaviour.