[Glycogen-rich clear-cell breast carcinoma with neuroendocrine differentiation features]

Glycogen-rich, clear cell carcinoma of the breast (GCC) is a rare type of breast cancer. Histological features are usually those of ductal carcinoma, but cases featuring lobular, tubular, and mixed ductal-tubular carcinoma have been reported. The presence of "numerous cells with clear cytoplasm" has been reported in some cases of primary neuro-endocrine tumors of the breast. Moreover, no case of GCC of the breast with neuro-endocrine features has been described. We report a case of 33-year-old woman with a palpable lump of the right breast. Fresh tissue obtained from the operating theatre was fixed in 10% formalin and routinely processed to paraffin. Serial sections were stained with haematoxylin and eosin (H&E), periodic acid Schiff (PAS) and PAS following diastase digestion (PASd); other sections were processed for immunohistological detection of chromogranin, synaptophysin, vimentin and smooth muscle actin. For electron microscopy, the tissue was fixed in 2.5% glutaraldehyde in cacodylate buffer. The samples were post-fixed in osmium, dehydrated in ethanol and embedded in araldite. Thin sections, counterstained in uranyl acetate and lead citrate, were studied under a Philips 400T electron microscope. The lump at histological examination was entirely composed of optically clear, neoplastic cells. The cytoplasm was filled with numerous PAS-positive granules which did not stain after the diastase digestion, leading to a diagnosis of GCC of the breast. Some histological (i.e. pattern of growth, blunt edges of neoplastic glands and numerous vessels) and cytological features (i.e. nuclear monomorphism and fine chromatin) prompted us to investigate the possible neuro-endocrine differentiation of the lesion. Immunohistochemical and ultrastructural studies strongly support such hypothesis. To the best of our knowledge, we report the first case of GCC of the breast with neuro-endocrine features.