The patient was a 44-year-old woman with suspected Stevens-Johnson syndrome due to Baktar® (sulfamethoxazole trimethoprim) medication received at our outpatient dermatology clinic. Histopathological examination of the epidermis, dermis, and subcutaneous adipose tissue samples showed numerous necrotic keratinocytes in the epidermis. Apoptotic nuclei were visualized as diaminobenzidine brown deposits with immunoperoxidase staining for cleaved caspase-3. Cleaved-caspase3-positive findings were consistent with eosinophilic material that appeared to be necrotic cells within the epidermis. Therefore, these eosinophilic materials must be apoptotic bodies. Generally speaking, and especially in Japan, these materials are considered necrotic keratinocytes. To our best knowledge, no studies have used apoptotic immunohistochemical markers to examine whether these structures are apoptotic.

Simple cysts (SCs) within the testes are rare in adults. The testicular SC lining comprises mesothelial cells. This report presents a case involving the accidental discovery of a castration-worthy SC in the right testis of a Japanese man in his 90s who was diagnosed with prostatic adenocarcinoma. Microscopic analysis revealed that the cystic wall was covered with flat to cuboidal mesothelial cells. Immunohistochemistry demonstrated mesothelial cell positivity for calretinin, Wilms tumor 1 (WT-1), Hector Battifora mesothelial epitope-1 (HBME-1), and cyclin-dependent kinase inhibitor p16 (p16INK4a). Notably, no human papillomavirus (HPV) in situ hybridization was detected. This report outlines an exceptionally rare instance of a simple cyst within the testis, suggesting the possibility of its origin from ectopic rete testis epithelium. This marks the inaugural documentation in the English literature of an SC within the testis found incidentally during castration for prostatic cancer.

We report a case of colloid carcinoma (CC) arising from an intestinal-type intraductal papillary mucinous neoplasm with high-grade dysplasia (IPMNHGD) of the pancreas, diagnosed with serial pancreatic juice aspiration cytological examination (SPACE). A rapidly growing intraductal papillary mucinous neoplasm (IPMN) in a 71-year-old Japanese man accelerated his hospitalization in our institute. Clinically, a large, ruptured pancreatic cyst was suspected. Cytologically, several mucin-positive signet-ring cells were scattered in the inflammatory, necrotic, or mucinous background. Signet-ring cells in cell block specimens were immunoreactive for MUC2, MUC5AC, maspin, S100P, and claudin-18. The final cytologic diagnosis was CC arising in an intestinal-type IPMNHGD with intraperitoneal penetration. The patient died two months postoperatively. The cytologic diagnosis was achieved through SPACE, and the presence of signet-ring cells was characteristic. Anti-claudin-18.2-specific monoclonal antibody therapy will likely be used to treat patients with IPMNHGD in the future. To our knowledge, this is the first report in English on mucin-positive signet-ring cells of CC arising in an intestinal-type IPMNHGD evaluated by SPACE cytology.

Hyperplastic nodules (HNs) are benign polypoid lesions of the colorectal mucosa reportedly caused by hyperplasia of the crypt epithelial cells. They differ from hyperplastic polyps because the crypts do not have histologically serrated changes. HNs often occur in the rectal mucosa and tend to be multifocal. We have proposed a new colitis nucleomigrans (CN) concept as the third type of microscopic colitis. Our histopathological criteria of CN include: i) chained nuclear migration to the middle part of the surface-lining columnar epithelium, ii) apoptotic nuclear debris scattered in the eosinophilic cytoplasm underneath the nuclei, and iii) mild to moderate chronic inflammation in the lamina propria. Immunostaining for cleaved-caspase 3 revealed apoptotic bodies. In this study, we report that most HN lesions share the histological features with CN, representing polypoid CN. We evaluated 108 lesions of HN in total, and 94 (87%) were reclassified as polypoid CN. In the polypoid CN, the lamina propria mucosae were uniformly edematous, suggesting that accelerated apoptosis of the mucosal surface epithelium may cause osmotic dysregulation to form localized mucosal elevations.