Cytokeratin 7 negative invasive breast carcinoma: clinicopathological and immunohistochemical analysis of 14 cases with clinical follow-up.

Cytokeratin 7 (CK 7) negative breast tumours are reported to occur rarely. We studied 14 CK 7 negative cases of primary invasive ductal carcinoma (IDC) detected during sentinel lymph node metastases work-up and immunohistochemistry panel in the work-up of metastatic carcinoma of unknown origin. Axillary lymph node metastases were present in seven patients (50%). Oestrogen receptor (ER) was strongly positive in all cases: progesterone receptor in 78%, Her-2/neu in 7% and high proliferation index with Ki-67 >20% was seen in 71% of the cases. Metastatic and/or recurrence were found in 8 of 14 patients (57%) with the mean clinical follow-up of 55 months. Metastatic sites include multiple bones, brain, spinal cord, liver, pancreas, ovary, lung, lymph node other than ipsilateral axillary and skin. 12 of 14 patients received adjuvant chemotherapy. All 14 patients received hormonal therapy and radiation therapy. Morphologically, IDC with neuroendocrine features was noted in 57%. Synaptophysin stain was positive in 57% and chromogranin was positive in 21% of the cases. In conclusion, these CK 7 negative breast carcinomas were ER positive, mostly Her-2/neu negative, had high Ki-67 and frequently showed neuroendocrine differentiation. More than half of these cases had a poor outcome.