Ductal carcinoma in situ (DCIS) represents a small number of cases in countries with inadequate breast cancer screening programs, and in the majority of cases is diagnosed as a palpable lump. It has been proposed that DCIS with palpable lump > or = 2.5 cm can be associated with microinvasion or invasive carcinoma and risk of axillary metastasis. The purpose of the present study is to evaluate incidence of microinvasion, invasion, and the role of lymphatic mapping and sentinel lymph node biopsy in DCIS > or = 2.5 cm. We conducted a retrospective analysis of patients with histologically proven incisional, excisional, or core biopsy of DCIS lump > or = 2.5 cm at a tertiary-care hospital. All patients underwent lymphatic mapping with sentinel lymph node biopsy.A total of 24 patients were included with average tumor size of 4 cm (range, 2.5-6 cm); 29% had microinvasive and 12.5% had invasive disease, three patients (12.5%) had positive sentinel lymph node, all had micrometastasis, and no metastasis were found in non-sentinel lymph nodes. Incidence of microinvasion and invasion were directly related with tumor size (10% for DCIS tumor size of 2.5-3.5 cm, 57% for 3.6-4.5 cm, and 71% for tumors between 4.5 and 6 cm). In addition, axillary metastasis incidence had a direct relationship with tumor size. (0% in 2.5-3.5-cm tumor size, 14% for 3.6-4.5 cm, and 28% in DCIS between 4.6 and 6.0 cm). The present study shows high incidence of microinvasion and invasion in DCIS diagnosed in tumors > or = 2.5 cm and supports the importance of axillary evaluation in patients with tumors >3.5 cm by means of lymphatic mapping and sentinel lymph node biopsy.