| Abstract: | ABSTRACT: BACKGROUND: After skin cancer, breast cancer is the most common malignancy in women. Tumors of unknown origin account for 5-15% of malignant neoplasms, with 1.5% corresponding to breast cancer. We selected an immunohistochemical panel with conventional and newer markers, such as mammaglobin, for the detection of neoplastic cells of breast origin. The specific objectives are: 1) to determine the sensitivity and specificity of the panel, with an especial emphasis on the inclusion of the mammaglobin marker, and 2) to compare immunohistochemistry performed on whole tissue sections and on Tissue Micro-Array. Methods. Twenty-nine metastatic breast tumors were included and assumed as tumors of unknown origin. Other 48 biopsies of other tissues were selected and assumed as negative controls. Tissue Micro-Array was performed. Immunohistochemistry for mammaglobin, gross cystic disease fluid protein-15, estrogen receptor, progesterone receptor and cytokeratin 7 was done. Results. Mammaglobin positive staining was observed in 10/29 cases, in 13/29 cases for gross cystic disease fluid protein-15, in 20/29 cases for estrogen receptor, 9/29 cases for progesterone receptor, and in 25/29 cases for cytokeratin 7. Among the negative controls, mammaglobin was positive in 2/48, and gross cystic disease fluid protein-15 in 4/48. Conclusions. The inclusion of MAG antibody in the immunohistochemical panel for the detection of tumors of unknown origin increased the probability of detecting metastasis of breast cancer. For the diagnostic strategy with the highest positive predictive value (87.5%), hormone receptors and mammaglobin were considered in serial, non-parallel manner. |
