Introduction/Background In Europe, endometrial cancer is the fourth most common cause of cancer among women and the most common gynecologic malignancy. Squamous endometrial carcinoma represents an uncommon histology, consisting of 3% of all Type II (non-endometroid) tumors.

Methodology The following is a rare case of squamous endometrial carcinoma diagnosed and treated at ‘Ramon y Cajal’ University Hospital (Madrid, Spain).

Results A 57-year-old, gesta2, para2, woman debuted with an HSIL Pap-test and a single episode of postmenopausal bleeding. Cervical biopsy guided by colposcopy showed a moderately differentiated epidermoid carcinoma. SCC was 3,2. HPV was positive for 16 and 59 genotypes. Preoperative imaging showed no macroscopical tumour.

Radical hysterectomy and pelvic bilateral lymphadenectomy were performed. Hystology showed an infiltrating squamous endometrial carcinoma, FIGO stage IA, and negative lymph nodes. There was overexpression of p63 and p16 and HPV 16 sequencing.

Follow up: controls were negative for four years, after which vaginal Pap-test showed HSIL and HPV 16 persisted. A VAIN3 was located by vaginoscopy at the left vaginal wall. She underwent laser CO2 treatment of the vagina. Controls have been negative, with negative Pap-tests and HPV.

Conclusion Endometrial carcinoma is traditionally characterized as either endometrioid or nonendometrioid based on histopathologic phenotypes. However, molecular heterogeneity within the two types has become increasingly apparent, and the current classification and treatment paradigms have significant limitations.

Squamous endometrial carcinoma is a rare type II tumour, which etiology could be related to differentiation of pluripotent endometrial precursor cells, heterotopic cervical tissue, or even HPV infection. P16, a tumor suppressor protein that has been associated with HPV, was present in this case, as well as HPV 16. The clinical behaviour of this malignancy, including debut of VAIN3 in the follow-up, supports the similarity to cervical cancer. Therefore, we could consider the treatment and follow-up of squamous endometrial carcinoma as a cervical carcinoma.

Disclosure Nothing to disclose.