• Breast
• breast cancer
• breast pathology
• immunohistochemistry
• neuroendocrine tumours

Breast central papilloma is a benign papillary neoplasm usually arising in the subareolar region.1 Cancerous change in a central papilloma is exceptionally rare, and, to our knowledge, there are only a few reports describing this unique condition.2–4 In the WHO Classification of tumours of the breast published in 2003, neuroendocrine carcinoma (NEC) is classified as a special tumour entity representing only about 2–5% of invasive breast carcinomas.5 Herein, we describe the first case of an NEC arising from a central papilloma of the breast.

The patient was a premenopausal Japanese woman, 43 years of age, with a clinical symptom of bloody nipple discharge from the left breast. Ultrasonography revealed a well-defined, localised solid mass in a dilated large duct immediately beneath her left nipple, suggesting an intraductal papilloma (figure 1).

On the cut surface of the lumpectomy specimen from the left breast, a circumscribed grey-whitish tumour was found in a prominently dilated lactiferous duct. Histopathologically, this intracystic tumour was supported by arborised and/or intricate fibrovascular cores lined with myoepithelial cells within a proliferation of two different types of epithelial cells: benign ductal cells and bland-appearing carcinoma cells (figure 2A,B). Benign ductal cells closely lining the myoepithelial cells were cuboidal to columnar in shape with a relatively high nuclear/cytoplasmic ratio and somewhat densely stained nuclei (figure 2B). By contrast, …