We analyzed 301 consecutive cases of 1-14-mm invasive breast carcinomas documented in large-format histological sections to determine the distribution of invasive and in situ foci. We also aimed to determine whether this distribution was related to the frequency of demonstrable vascular invasion and lymph node metastases. One third of the carcinomas (31.9%, 96 cases) had a multifocal invasive component and a more than doubled relative risk of vascular invasion (RR = 2.3642, 95% confidence interval (CI) = 1.5077-3.7073) and lymph node metastasis (RR = 2.7760, 95% CI = 1.6337-4.7171) compared to unifocal invasive carcinomas. Invasive carcinomas with diffuse in situ component had an elevated relative risk for vascular invasion (RR = 2.2201, 95% CI = 1.4049-3.5083) and lymph node metastasis (RR = 1.9201, 95% CI = 1.1278-3.2691) compared to those with unifocal or multifocal in situ lesions. However, multifocality of the invasive component was associated with a substantially elevated risk of vascular invasion and lymph node metastasis, even in cases with diffuse in situ component. Similar observations were made in the 1-9- and 10-14-mm invasive carcinoma subgroups. These findings indicate that lesion distribution has prognostic relevance for 1-14-mm invasive breast carcinomas and underline the importance of using special techniques in breast pathology for proper assessment of this parameter.