A new study has reported that women with multifocal and/or diffuse tumors are almost twice as likely to die as women with single tumors, after controlling for tumor characteristics and treatment. The study was designed to investigate whether lesion distribution (unifocal, multifocal, or diffuse) and disease extent influence breast cancer survival. Unifocal disease is breast cancer with only one tumor whereas multifocal or multicentric breast cancer involves having more than one tumor in a given breast. In diffuse disease such as inflammatory breast cancer or LCIS (lobular carcinoma in situ), cancer cells are interspersed with normal cells instead of forming a solid cancerous mass.

The study included 574 breast cancer cases, 499 with invasive or invasive plus in situ disease (DCIS or LCIS), and 75 with in situ disease only. The invasive component was unifocal in 62% of the cases, multifocal in 24%, and diffuse in 5%. When the noninvasive disease was combined with the invasive tumor components, 48% of the cases were unifocal, 25% were multifocal, and 20% had diffuse disease. Sixty percent of the tumors were categorized as having limited extent (occupying an area less than 4 cm in largest dimension) and 29% were considered extensive.

Ten-year breast cancer-specific survival was found to be highest among women with unifocal invasive disease (89.6%), followed by those with multifocal invasive disease (76.0%), and diffuse invasive disease (63.6%). The 10-year breast cancer-specific survival rates when noninvasive and invasive disease were combined were found to be 92.3%, 82.3%, and 75.7%, respectively. Patients with extensive tumors had significantly lower 10-year survival (75.5%) compared to those with limited extent (91.6%) and an 1.89-fold risk of breast cancer-specific death after controlling for tumor attributes, type of surgery, and adjuvant therapy. Women with multifocal and/or diffuse tumors were almost twice as likely to die as women with unifocal disease, after controlling for the same factors. The authors conclude that lesion distribution and disease extent represent important independent survival-related prognostic parameters in breast cancer.