Superficial spreading cervical squamous cell carcinoma in situ with extensive endomyometrial infiltration masquerading as a primary endometrial cancer.

The presence of squamous cell carcinoma (SCC) on endometrial histology raises the possibility of a primary endometrial carcinoma, as well as secondary endometrial involvement by SCC from another site, especially the cervix. This distinction relies on numerous cardinal clinical and pathologic findings and may occasionally be problematic. We document an unusual tumour in a postmenopausal woman who presented with clinical and radiologic features of a primary endometrial cancer, confirmed on endometrial histology as a keratinising SCC. Subsequent pathologic evaluation of the hysterectomy specimen, however, demonstrated an exclusively in situ cervical SCC, with extensive endometrial intramucosal spread and widespread infiltration of the myometrium, macroscopically mimicking a primary endometrial neoplasm. We review the pathologic distinction between primary endometrial SCC and secondary corpus involvement of cervical SCC, as well as the broader differential diagnosis when SCC is identified on endometrial histology. [ABSTRACT FROM AUTHOR]