Infiltrating lobular carcinoma represents 7-10% of all invasive breast cancers. The greatest diameter of the tumors in the surgical specimens is required for an accurate T-staging. Tumors with dimension of zero cm, >0 to < or =2 cm, >2 to < or =5 cm, and >5 cm are staged as T0, T1, T2, and T3, respectively. A retrospective study on the specimens was performed on the specimens of 74 cases with infiltrating lobular carcinoma at the UCLA Medical Center from 2003 to 2005. The patients' ages ranged from 38 to 95 years. Specimens were from lumpectomy and mastectomy procedures on 36 and 38 patients, respectively. The specimens were divided in four groups according to the gross T-stages. Microscopic measurement of the tumors was carried out within each of the four groups for restaging purposes. Resizing of tumors was performed by marking the microscopic tumor extensions and compiling the measurements. In group 1, all 26 gross T0 tumors changed to T1 (69%), T2 (19%), and T3 (12%) after microscopic restaging. In group 2, 50% of the 26 gross T1 tumors became T2 (35%) and T3 (15%). In group 3, 9 (50%) of the T2 tumors changed to T3 microscopically. All 7 specimens (100%) in group 4 remained as T3. The results show that the gross measurements alone may underestimate 40-50% of the tumor T-stages. Therefore, the T-stages of the tumors with a gross size of 5 cm or less may change by microscopic resizing after an extensive sampling of the specimen.