A significantly different variant to the invasive ductal carcinomata, with the unique signature being loss of E-cadherin and cell adhesion. Metastatic spread differs from the more conventional ductal carcinoma.
These tumours usually present in the conventional method (mass, mammographic density) but a significant portion present with a more diffuse mass that is difficult to detect.
Lobular carcinoma is similar microscopically to atypical lobular hyperplasia and lobular carcinoma in situ. The cells are often rounded and discohesive. They do not form tubules and usually exist in single file or small clusters/sheets of cells.
Lobular carcinoma is staged using the modified Bloom Richardson system (measuring tubule formation, nuclear pleomorphism and mitotic rate). Overall tumour behaviour is similar to ductal carcinoma of a similar grade and stage.
The classical feature for lobular carcinoma is the loss of E-cadherin which can be measured using immunohistochemistry. Other immunohistochemical markers, such as the oestrogen and progesterone receptors and the ERBB2 receptor, can also be measured and often vary according to the grade of the tumour.
These tumours all show loss of E-cadherin. High grade tumours usually have amplification of ERBB2.