This is a cross-sectional and retrospective study of a cohort of patients with invasive lobular breast cancer (LBC) or in situ lobular neoplasia (LIN3). The main endpoint is the relative frequency of patients with a germline mutation using a recent panel including 113 genes from the Illumina protocol. In case of identification of a novel pathogenetic germline mutations, a personalized follow-up will be offered to each patient (in case of genes at moderate-, low-penetrance), or prophylactic mastectomy (in case of genes at high-penetrance). Breast screening in moderate-, low-penetrance mutated patients should be performed periodically using digital mammography, ultrasound and MRI, and will be routinely observed. Patients will be scheduled for follow-up at six-month intervals for 5 years at our outpatient clinic, and yearly thereafter