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).