Clinical impacts of histological subtyping primary breast cancer.

BACKGROUND Treatment decisions in breast cancer depend on TNM classification and the assessment of additional variables with have an impact on survival. We examined whether histological subtyping breast cancer as either ductal or lobular is related to disease outcome. PATIENTS AND METHODS We examined a large data base of 14198 breast cancer patients. RESULTS Histological sub-classification of invasive breast cancer as either ductal or lobular is not correlated with disease outcome. However, the data further showed that invasive lobular carcinomas have a higher probability of being oestrogen receptor (ER)- and progesterone receptor (PR)-positive and a lower probability of being c-erbB2-positive. They also showed a higher average age at the time of diagnosis in comparison with invasive ductal carcinoma. Local recurrence rates were lower in invasive lobular carcinoma in comparison with invasive ductal carcinoma (3.5% vs. 6.2%; p = 0.031). The multivariable Cox regression analysis showed that ER, PR, nodal status, grade and tumour size predicted disease outcome with statistical significance, while the histological subtype (invasive ductal or lobular) was not a significant predictor of disease outcome. CONCLUSION Histological sub-classification of invasive breast cancer as either ductal or lobular is not correlated with disease outcome. On the other hand our data gives some indication that lobular and ductal breast cancer appear to be different biological entities.