Metaplastic mammary carcinoma with osteoclast-like giant cells is a rare neoplasm, and the histogenesis of this tumor remains controversial. A case of metaplastic mammary carcinoma with osteoclast-like giant cells in a 72-year-old woman is reported with p53 mutational analysis. Microscopically, the tumor was composed of a dominant sarcomatous stromal component containing osteoclast-like giant cells and a minor component of intraductal carcinoma. Immunostaining for p53 revealed strong positivity in both intraductal and sarcomatous components, but not in osteoclast-like giant cells. Mutational analysis of the p53 gene disclosed an identical point mutation in both intraductal and sarcomatous components, but not in osteoclast-like giant cells, indicating that both components share the same progenitor cells, and osteoclast-like giant cells represent a reactive infiltrate.

We present a unique case of hepatocellular carcinoma with mucin-producing gland formation. A 53-year-old man with hepatitis B infection presented with weight loss for the past month. Computed tomography demonstrated a 10 × 9.8 cm mass in the right hepatic lobe accompanied by cirrhotic changes in the hepatic parenchyma. Right hepatectomy was performed, and the tumor cut surface showed a poorly-circumscribed, white to pink tumor with numerous nodules and extensive necrosis. Microscopically, the tumor was composed of thick trabeculae and large, irregularly-shaped islands, both of which were filled with pleomorphic eosinophilic hepatoid cells or gland-forming columnar cells with mucin production. Those cells were immunoreactive for cytokeratin 19 in both the trabeculae and the glands. In some tumor cells, limited immunoreactivity for cytokeratin 7, epithelial membrane antigen and carcinoembryonic antigen was noted. The cells forming thick trabeculae were focally positive for hepatocyte paraffin 1 and alpha-fetoprotein. We suggest that this tumor shows bidirectional differentiation into hepatocytes and cholangiocytes, supporting the concepts that human hepatocarcinogenesis can be based on transformation of progenitor cells which can imply divergent differentiation.