Comparative estimation of histological structure of contralateral tumors in 104 patients with primary and in 54--with metastatic mammarial gland cancer (MGC) was performed. Revealing of various histological types of tumoral nodes--of a one component infiltrating ductal cancer (IDC) in one mammarial gland and a one-component infiltrating lobular cancer (IPC)--in another one, combination of special form of the MGC with IDC and/or IPC, combination of cancer in situ with invasive form of the MGC constitutes the criterion of primarily-multiple affection. In differentiated diagnosis of primary and metastatic tumor this criterion is highly specific (92.9%), but has low prognostic value (37.5%). That's why in 73% of women-patients it is necessary to analyze the clinical examination data in addition to establish the diagnosis of primary bilateral MGC.