Approach and nomenclature problems of extracutaneous basaloid neoplasias of visceral organs with three cases of basaloid carcinoma described for the first time in the urinary bladder.

Pure basal cell carcinomas/basaloid carcinomas (BCC/BC) from only basal cells in the urinary bladder have not been reported so far. Our aim in this study was to present three BC cases showing distinct pilomatrixoma-like keratinization (matrixial) and sebaceous differentiation in the bladder in transurethral resection material, without urothelial and squamous carcinoma components, and to discuss the concept of BCC/BC in visceral organs. In three cases, it invaded the muscularis propria. Immunohistochemically, Keratin-7 and EMA were almost completely negative, while GATA3 was positive in very few cells. p63, keratin-5,6 and bcl2 were positive in all three tumors. Adipophilin was positive in areas of sebaceous differentiation. BCC/BC are very rare in visceral organs and had different nomenclatures. These show different patterns and variants, and have different nomenclature depending on the histological diversity/embryological development of the organ in which they are localized. We also noticed that adenoid cystic carcinoma and basaloid carcinoma have similar histology and are transitional to each other in many organs, necessitating a common nomenclature.