Primary Squamous Cell Carcinoma of the Upper Genital Tract: Utility of p16 INK4a Expression and HPV DNA Status in its Differential Diagnosis from Extended Cervical Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) involving the upper genital tract, including the endometrium, fallopian tubes, and ovarian surface, is extremely rare, with most patients described in single case reports.1-5 Its possible pathogenic mechanisms include 1) de novo carcinogenesis; 2) extensive squamous metaplasia (ichthyosis uteri) in the mucosa of the upper genital tract with subsequent malignant transformation; 3) endometrioid adenocarcinoma with predominantly squamous differentiation; and 4) mucosal spread from cervical SCC.6 Differentiating primary SCC arising in the upper genital tract from primary cervical SCC extending to the upper genital tract is clinically important for tumor staging and patient management, especially since the locoregional recurrence rate is higher and the disease-free survival rate is lower in cervical SCC patients with endometrial involvement than it is in patients without endometrial involvement.7 The diagnostic criteria for primary SCC of the endometrium include the absence of 1) coexisting endometrial adenocarcino adenocarcinoma; 2) a connection between endometrial SCC and the squamous epithelium of the cervix; and 3) a primary squamous lesion in the cervix, either in situ SCC or invasive carcinoma.8 We have found it difficult, however, to determine the primary sites of SCCs detected in a fallopian tube or ovary in patients who have undergone prior hysterectomy with insufficient histological examination of the uterine cervix at the time of surgery. Human papillomavirus (HPV) infection has been associated with the development of cervical SCC, and p16INK4a, a surrogate marker for HPV infection, is consistently positive in HPV-associated cervical SCCs and precancerous squamous intraepithelial lesions.9 However, the cause of disease and the utility of p16INK4a expression and HPV DNA status have not been clearly determined in patients with primary SCC of the upper genital tract. To determine the utility of p16INK4a expression and HPV DNA status in identifying the primary tumor site, we compared these markers as well as the histologic findings in four patients with primary SCCs of the upper genital tract and in five patients with cervical SCCs extending to the mucosa of the upper genital tract.