Cytologic diagnosis of vaginal papillary squamotransitional cell carcinoma. A case report

Papillary squamous and squamotransitional cell carcinomas of the cervix and vagina are infrequent morphologic variants of squamous cell carcinoma that may be underdiagnosed due to a bland histologic appearance. To our knowledge, this entity has not been previously detected by Pap smear evaluation.

Vaginal wall pap smears were collected from a patient with a previous hysterectomy for microinvasive cervicovaginal squamous cell carcinoma and extensive carcinoma in situ. The smears were characterized by: (1) large, darkly staining, three-dimensional, branching, papillary epithelial fragments with prominent fibrovascular cores and lined with loosely cohesive epithelial cells; (2) a highly cellular background population of dissociated single epithelial cells with features of severe dysplasia, including hyperchromatic, coarse chromatin; scant, delicate, frayed cytoplasm and karyorrhectic debris; (3) syncytial aggregates of severely dysplastic epithelial cells morphologically similar to the single cells; and (4) lack of a recognizable, morphologically distinct "transitional cell" population.

Papillary squamotransitional cell carcinoma of the vagina is a rare morphologic variant of squamous cell carcinoma that should be distinguished from benign vaginal squamous papillomas, condylomatous lesions and verrucous carcinoma. However, this lesion is also related to human papillomavirus infection, particularly the high-risk types. Papillary squamotransitional cell carcinoma can be suspected on Pap smear when high grade squamous intraepithelial lesion features are found in combination with three-dimensional papillary tissue fragments with prominent fibrovascular cores.