KRT20 and large cell neuroendocrine carcinoma: 7 Okoshi Okoshi K K Saiga Saiga T T Hisamori Hisamori S S Iwaisako Iwaisako K K Kobayashi Kobayashi H H Ogawa Ogawa H H A case of cytokeratin 20-positive large-cell neuroendocrine carcinoma of the breast A case of cytokeratin 20-positive large-cell neuroendocrine carcinoma of the breast Breast Cancer.