Bilateral breast core-biopsy: 

Microscopy: The tumour is composed of highly cellular sheets and solid nests of tumour cells, surrounded by a fibroblastic stromal response. Tumour cells have hyperchromatic, angulated nuclei with dispersed chromatin and scant cytoplasm. Mitotic figures and apoptotic bodies are very frequent. Nuclear moulding and streaking are a feature. Very focally, there are regions comprising nests of tumour cells with more abundant eosinophilic cytoplasm, but these foci occupy represent <5% of the tumour. No lymphovascular or perineural invasion is identified. No in situ carcinoma is seen.

Immunoperoxidase stains: 

  • Positive: broad-spectrum cytokeratin (AE 1/3, paranuclear dot), synaptophysin, chromogranin
  • Negative: ER, PR, Her2
  • Ki67 shows a proliferative index of approximately 90%

Conclusion: Bilateral breast core biopsies: All specimens show poorly differentiated neuroendocrine carcinoma (small cell carcinoma).

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