Snapshot A 62-year-old women presents to her primary care physician with a mass in the right breast, which she believes was the result of trauma. On exam there is a firm, fixed 1 cm mass in the right breast in the upper outer quandrant. There is no axillary lyphadenopathy. Introduction Overview a non-invasive lesion due to proliferative changes within the breast lobule not a premalignant lesion considered a risk factor for breast cancer if untreated LCIS will become invasive in 20-30% of patients over a prolonged period of time (10-15 years) 7-11x higher risk of developing invasive breast cancer in a patient with LCIS login to view 2 more bullets Epidemiology Incidence ~10% of "malignant" lesions on mammogram lifetime risk is 1% per year Risk factors age > 40 years family history of breast cancer hormone replacement therapy ETIOLOGY Genetics mutations LCIS cells are usually estrogen/progesterone receptor-positive and HER2/neu-negative Presentation Symptoms asymptomatic breast lump Physical exam breast lump may be detected on exam or may not be palpable Imaging Mammography indications screening login to view 4 more bullets diagnosis of breast lump findings LCIS not readily visible on mammography STUDIES Core needle biopsy indications diagnosis login to view 3 more bullets Differential Ductal carcinoma in situ (DCIS) key distinguishing feature histology login to view 4 more bullets Treatment Medical tamoxifen indications login to view 1 more bullet close follow-up frequent scheduled exams mammographic screening of both breasts Surgical excisional biopsy indications login to view 1 more bullet bilateral mastectomy indications login to view 2 more bullets Complications Development of invasive carcinoma Prognosis Very good majority of women with LCIS will not develop invasive breast cancer