Clinical significance of neuroendocrine carcinoma of the breast

Background: Neuroendocrine (NE) carcinomas of the breast are defined by the diffuse expression of NE markers. This definition includes lesions with 'p ure' NE phenotype as well as 'variants' which may co-express mucinous and/o r apocrine phenotype. In the present work, the clinical significance of 'pu re' NE differentiation in breast carcinoma and of its 'variants' will be an alyzed. Materials and methods: Forty-three NE breast carcinomas immunocytochemicall y positive for chromogranins and/or synaptophysin in greater than or equal to 50% of cells were graded following the Elston and Ellis grading system f or breast carcinomas. The production of mucin and the expression of the apo crine marker Gross Cystic Disease Fluid Protein-15 (GCDFP-15) were correlat ed with the grade and the hormonal receptor status. The clinical outcome of patients was also analyzed. Results: The histological grade highly influenced the clinical evolution of NE breast carcinomas. We confirmed that mucinous differentiation is an imp ortant indicator of low biological aggressiveness. Estrogen and progesteron e receptor expression was also correlated with a better prognosis. Presence of androgen was correlated with the expression of GCDFP-15 in NE tumors. Conclusions: The histological grade overcomes the immunophenotype in determ ining the prognosis of NE differentiated carcinomas of the breast. Co-expre ssion of exocrine products in such tumors is related to hormone dependency.