MEDULLARY CARCINOMA OF THE BREAST - A MULTICENTER STUDY OF ITS DIAGNOSTIC CONSISTENCY

Nine pathologists from different institutions reviewed in a double-bli nd study 16 breast tumors previously indexed as typical medullary carc inoma, atypical medullary carcinoma, or infiltrative ductal carcinoma. A set of 16 slides was circulated two times among the nine pathologis ts. The diagnoses of typical and atypical medullary carcinomas were ba sed on a definition given by Ridolfi et al. The interobserver and intr aobserver agreement was low, with a kappa value of less than .50. The only histological criterion that had more than 50% agreement was the p resence or absence of an in situ component in the tumor, assuming that the disagreement of one pathologist is accepted. This study is a snap shot of the problems encountered in the diagnosis of typical medullary carcinoma in a routine context and it shows high levels of variations in diagnostic consistency.