Background: Primary squamous cell carcinoma of the endometrium is exceedingly rare. It has been described in association with pyometra but its etiology is still unclear.
Case: The authors report the case of a 75-year-old woman who presented with pelvic pain and pyometra. No gross tumor was identified in the uterus; however, extensive epidermalization of the endometrial mucosa was noted. Microscopic findings were consistent with a primary in situ squamous carcinoma of the endometrium associated with extensive squamous metaplasia and areas of dysplasia. HPV antigen and DNA detection were negative in both the endometrial lesions and the cervix.
Conclusions: These results support the sequence of change with squamous metaplasia, progressing through dysplasia to carcinoma as a possible pathogenetic process. HPV's role, however, remains uncertain.