Prognostic significance of molecular classification of breast invasive ductal carcinoma

Breast carcinoma classification has dramatically changed in recent years following application of molecular techniques. Immunohistochemistry can help select patients for different therapies. The objective of the present report is to determine the prognostic influence of the molecular classification of breast carcinoma with immunohistochemistry.

We have retrospectively selected a cohort of 257 patients with invasive ductal carcinoma NOS diagnosed and treated in the same hospital between 1997 and 2000. We have classified the cases in four tumor types according to the immunohistochemical expression of several markers, as luminal A tumors [estrogen and/or progesterone receptors (ER/PE) positive and Her-2 negative]; luminal B tumors (ER/PR positive and Her-2 positive); Her-2 positive tumors (ER/PR negative with Her-2 positive); and triple negative phenotype (all markers negative).

In our series, 116 patients had tumors of luminal A type (47.93%); 67 (27.68%) were luminal type B; 33 (13.63%) were Her2 positive; and 26 (10.74%) were triple negative. The recurrence rate was 19% for luminal type A tumors, 25.4% for luminal type B, 39.4% for Her2 positive and 30.8% for triple negative lesions. The mean relapse free survival was 79.07, 73.07, 64.3 and 83,5 months for luminal A and B, Her-2 and triple negative lesions, respectively. Mortality rate reached 11.2% for luminal A tumors compared with 19.4, 33.3 and 26.9% for luminal B, Her2 and triple negative tumors, respectively. The mean overall survival for these groups was 88.42, 81.41, 77.62 and 93.6 months.

Molecular classification with immunohistochemistry behaves as a significant prognosticator for breast invasive ductal carcinoma in our series of patients. The worse prognosis observed for Her2 expressing lesions may have changed after trastuzumab use.