MEDULLARY CARCINOMA OF THE BREAST - A TUMOR LACKING KERATIN-19

The presence of keratin 19 (K19) was searched for by immunostaining in 16 medullary carcinomas, comprising 12 typical and four atypical case s, in 29 undifferentiated high-grade carcinomas (NOS-HG) with conspicu ous lymphoid response and in 12 well differentiated low-grade carcinom as (NOS-LG). The medullary carcinomas were all negative whereas 23 of the high-grade and all 12 low-grade carcinomas expressed K19. Staining for K19 could be of value in the differential diagnosis of these tumo urs. Furthermore, these findings, with other observations, raise the p ossibility that medullary carcinoma cells could be linked to precursor cells of the terminal duct lobular units because both populations sha re several characteristics.