OBJECTIVE: Our objective was to determine the degree with which mammographic features predict the presence and size of invasive carcinomas associated with malignant mammographic microcalcification lesions without a mass. MATERIALS AND METHODS: Mammographic features were correlated with pathologic features in 304 consecutive breast carcinomas manifested by mammographic calcifications only in a prospective evaluation. RESULTS: Mammographic calcifications associated with breast carcinoma had the final pathologic diagnoses of pure ductal carcinoma in situ (DCIS) in 65% of patients, DCIS with a focus of invasion in 32%, and invasive carcinoma only in 4%. Invasive foci were more likely associated with mammographic calcification size of 11 mm and greater (40%, 77/194) compared with 1-10 mm (26%, 29/110; p = 0.019). Invasive foci were also more likely associated with linear calcifications (44%, 55/126) compared with granular calcifications (29%, 51/178; p = 0.007). The frequency of invasion did not increase with calcification extents greater than 10 mm. The frequency of invasion ranged from 22% for less than or equal to 5-mm granular calcifications to 45% for linear calcifications of 11 mm and greater. Only 11% of cancers characterized by fine granular calcifications were associated with invasion as compared with 32% of those with coarse and mixed granular calcifications (p = 0.002). CONCLUSION: Mammographic calcification features of malignant lesions cannot predict the absence of invasion with greater than 90% predictive value or predict the presence of invasion with greater than 45% predictive value. Increased extent of calcifications greater than 10 mm was not associated with greater likelihood of invasion.