Case report: HPV related pelvic retroperitoneal squamous cell cancer of unknown primary presenting as ovary neoplasm

Retroperitoneal tumors (RPTs) of the pelvis are rare and often present asymptomatically. We report a rare case of human papillomavirus (HPV)-related primary retroperitoneal squamous cell carcinoma (PRSCC) that was preoperatively misdiagnosed as adnexal cancer.

A menopausal 59-year-old woman presented with right leg pain persisting for two months. Imaging revealed a heterogeneous lesion in the right adnexal area; however, the uterus and left ovary appeared normal. Laboratory tests showed slightly elevated levels of cancer 125 (CA 125) and squamous cell carcinoma (SCC) antigens. The patient underwent surgical staging for the suspected ovarian cancer. Intraoperatively, the bilateral adnexa and uterus appeared normal. A lesion identified in the right pelvic retroperitoneal cavity was resected and its pathological analysis revealed SCC and cervical intraepithelial neoplasia III (CIN III) and immunohistochemical expression of cyclin-dependent kinase inhibitor 2A (p16) in the cervix. HPV 16 was identified by a polymerase chain reaction (PCR). The patient chose not to undergo any additional postoperative treatment. Her leg pain disappeared the day after the procedure but recurred a year later. A new tumor was detected on computed tomography (CT) in the same area.

PRSCC is rare and can be misdiagnosed as a gynaecological neoplasm. HPV can migrate to the retroperitoneal space and act as a carcinogen in this location.

HPV infection may contribute to the development of PRSCC. Complete surgical resection, with adjuvant radiotherapy and chemotherapy, is a viable treatment approach.