Interobserver variation in the identification of breast carcinoma in intramammary lymphatics

Nine surgical pathologists participated in a microscopic review of 35 cases of pT1-2 N0 M0 breast carcinoma. The pathologists outlined strict criteria for the identification of intramammary lymphatics and blood vessels and for the identification of cancerous emboli in these vascular channels. Each mastectomy case was studied by three different pathologists. All three concurred on the presence or absence of intralymphatic cancer in 12 of the 35 cases. Observers agreed on the absence of blood vessel invasion in 30 of the 35 cases. There was no consistent bias on the part of a single reviewer, either alone or with another pathologist, in identifying the emboli. We conclude that the identification of intralymphatic cancerous emboli in mastectomy specimens is not a reliably reproducible prognostic finding on which recommendation of systemic chemotherapy in stage I breast carcinoma patients can be based.