Clinical Differences between Invasive Lobular Breast Cancer and Invasive Carcinoma of No Special Type in the German Mammography-Screening-Program

Invasive lobular carcinoma (ILC) of the breast is known to have typical molecular, clinical, and pathological characteristics that differ from invasive cancer of no special type (NST). In the German mammography screening program (MSP), we evaluated clinical differences between these tumor types at the time of their detection. Clinical features of NSTs (n = 785) and ILCs (n = 141) diagnosed in the MSP between 2009 and 2016 were compared. Compared to NST, ILC was significantly correlated with advanced age (59.1 years versus 60.6 years) and larger tumor size (1.5 cm versus 2.3 cm). ILC was significantly more frequently associated with moderate tumor differentiation (G2), whereas NST was associated with a higher rate of poorly differentiated tumors (p < .001). Furthermore, ILC presented more often as multifocal tumors (36% versus 11%, p < .001), and mastectomies were performed more often in the ILC group (27% versus 12%, p < .001). ILCs and NSTs had different clinical features at the time of detection. The pathological profile of ILC may explain some of these features. Specialists should be aware of the fact that ILC may escape detection by conventional imaging modalities for a long time, and may present later in life as more advanced multifocal disease.