MEDULLARY CARCINOMA OF THE BREAST - INTEROBSERVER VARIABILITY IN HISTOPATHOLOGIC DIAGNOSIS

To assess the interobserver reproducibility for the diagnosis of medul lary carcinoma of the breast (MC), 53 previously diagnosed MCs were in dependently assessed by six observers for growth pattern, nuclear grad e (NG), inflammation, tumor margin, intraductal component, and glandul ar features. Tumors were reclassified as MC, atypical MC, or infiltrat ing ductal carcinoma according to the histopathologic criteria of Rido lfi et al. (Cancer 40:1365, 1977), Wargotz and Silverberg (Hum Pathol 19:1340, 1988), and Pedersen et al. (Br J Cancer 63:591, 1991). NG was the most reproducible parameter, and tumor margin was the least, with consensus agreement by four of six observers for 49 (92%) and 26 (49% ) of cases, respectively. Utilizing the histopathologic criteria propo sed by Ridolfi et al., Wargotz and Silverberg, and Pedersen et al., co nsensus diagnoses were achieved in 37 cases (70%), 46 cases (87%), and 51 cases (96%), respectively. A consensus diagnosis of MC in all thre e systems was unassociated with tumor size, axillary lymph node status or overall survival (median follow-up: 89 mo). The consensus (or bett er) reclassification of 44/53 (83%), 35/53 (66%), and 27/53 (51%) prev iously diagnosed MC as atypical MC or infiltrating ductal carcinoma by the criteria of Ridolfi et al., Wargotz and Silverberg, and Pedersen et al., respectively, suggests that MC was previously overdiagnosed. W hile the scheme of Pedersen et al. is the most reproducible, additiona l follow-up information is necessary to determine the biological signi ficance of this classification system. To minimize these difficulties in practice, pathologists should carefully adhere to published criteri a and indicate the classification system utilized.