Cervical Adenoid Basal Carcinoma With High-grade Squamous Component: True Mixed Carcinoma or Colonization of Adenoid...

Adenoid basal carcinoma (ABC) is a rare clinically indolent human papillomavirus-associated cervical neoplasm with uniformly bland morphology which in pure form does not metastasize. Many cases co-exist with a human papillomavirus-associated high-grade squamous intraepithelial lesion (HSIL) or squamous cell carcinoma (SCC). The ABC and high-grade squamous components may be clearly separate, albeit intermingled, and when the high-grade squamous component is invasive, the tumor is designated a mixed carcinoma, with clinical behavior determined by the non-ABC component. In other cases, discrete nests of high-grade atypical squamous cells are intimately admixed and incorporated within the ABC. These are more difficult to classify but are also usually reported as mixed carcinomas. Herein, we report a series of 9 cases of ABC in patients aged 33 to 89 years (mean age: 63 y) with a high-grade squamous component. In 7 cases, the high-grade squamous cells partly replaced and expanded the nests of ABC, sometimes with a residual cuff of ABC cells, while in the other 2 cases the ABC and SCC were clearly separate. We propose that the aforementioned 7 cases represent colonization of ABC by HSIL rather than mixed carcinomas; as far as we are aware, this concept has not been proposed before. In all cases which we feel represent colonization of ABC by HSIL, the tumors were confined to the cervix (stages IA1 [3 tumors], IA2 [2 tumors], IB1 [2 tumors]) and follow-up was unremarkable with no evidence of metastasis. One case with separate components of ABC and SCC was stage IVA at diagnosis and the patient died of disease. The other was stage IB1 at diagnosis and the patient died of unrelated causes at 13 months. We discuss the clinical implications of distinguishing true mixed carcinomas from colonization of ABC by HSIL and provide an approach to diagnosis. We also report a unique case of colonization of so-called cervical ectopic prostatic tissue by HSIL.