The prognostic importance of syncytial growth pattern in medullary carcinoma of the breast.

The histopathological criteria for medullary carcinoma of the breast (MC) used by most pathologists today were delineated by Ridolfi et al. in 1977. The prime criterion is: "A predominantly syncytial growth pattern", predominantly being defined as including 75% or more of the tumour. However, no indication has been given as to why this limit was set at 75%. The present study analyzes the prognostic importance of the extent of syncytial growth in a population of 102 breast cancers with medullary features. Generally, we find a positive prognostic influence of an extensive syncytial growth. The prognostic importance of setting the limit for predominantly syncytial growth at 90% and at 75%, respectively, is evaluated. This comparative study provides no basis for changing the definition of predominantly syncytial growth pattern.