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

BACKGROUND: Primary squamous cell carcinoma (SCC) of the upper genital tract, including the endometrium, fallopian tubes, and ovaries, is extremely rare. It must be distinguished from the mucosal extension of primary cervical SCC because determination of the primary tumor site is important for tumor staging. However, patients with SCC of the fallopian tubes or ovarian surface have often undergone prior hysterectomy with inadequate examination of the cervix, making it difficult to determine the primary site. METHODS: We compared histologic findings, p16(INK4a) expression, and human papillomavirus (HPV) DNA status in four patients with primary SCC of the upper genital tract and five patients with primary cervical SCC extending to the mucosa of the upper genital tract. RESULTS: All five SCCs of cervical origin showed strong expression of p16(INK4a), whereas all four SCCs of the upper genital tract were negative, although one showed weak focal staining. Three of the five cervical SCCs were positive for HPV16 DNA, whereas all four primary SCCs of the upper genital tract were negative for HPV DNA. CONCLUSIONS: Although a thorough histological examination is important, immunonegativity for p16(INK4a) and negative for HPV DNA may be useful adjuncts in determining primary SCCs of the upper genital tract.