A spontaneous thymic carcinosarcoma in a young Sprague Dawley rat.

We encountered a case of spontaneous thymic carcinosarcoma in a young Crl:CD (Sprague Dawley) rat. Grossly, a white multinodular mass replaced the thymus in the thoracic cavity. Histologically, multiple nodules were separated by fibrous stroma, and each nodule included isolated regions that were composed of epithelial or non-epithelial tumor cells. The epithelial tumor cells were relatively large and round to polygonal cells with large nuclei and weakly eosinophilic cytoplasm. These cells were cytokeratin-positive and vimentin-negative. These cells infiltrated the lungs. The non-epithelial tumor cells were poorly differentiated, small, round to spindle-shaped cells with small nuclei and basophilic cytoplasm. These cells were vimentin-positive and mostly cytokeratin-negative. Many islands of cartilage were observed near non-epithelial cells. Based on these findings, the tumor was diagnosed as a primary thymic carcinosarcoma consisting of a malignant thymoma composed of epithelial tumor cells and a mesenchymal chondrosarcoma composed of non-epithelial tumor cells.

Irreversible metronidazole encephalopathy in an elderly woman with primary biliary cholangitis.

An 82-year-old woman with primary biliary cholangitis was diagnosed with an irreversible neurological disorder, caused by metronidazole (MNZ)-induced encephalopathy. Although the disorder is a reversible pathological condition, in rare cases, it can cause serious sequelae or could even be fatal. Therefore, medications should be administered carefully, particularly in patients who require long-term administration of large doses or those with liver dysfunction.