Endometrial Carcinoma Grade 1 with Squamous Metaplasia Involving the Lower Uterine Segment. Dr. Jaume Ordi, Hospital Clinic, Barcelona, Spain

Clinical History 59-year-old woman presented with uterine bleeding. An endometrial curettage showed an endometrial carcinoma. A total hysterectomy with bilateral salpingo-oophorectomy was performed. The section includes the lower uterine segment and the endocervical canal. Figure 1 Click to view with ImageScope Click to view with a Web-Based Viewer Pathologic features The uterus showed a 2 cm endometrial tumor located in the lower uterine segment. Histological analysis revealed a well-differentiated endometrial adenocarcinoma with small foci of squamous differentiation. No myometrial invasion was identified. The tumor involved the endocervical canal. The uterine cervix showed a squamous intraepithelial carcinoma grade 3 (CIN3) and foci of in situ endocervical carcinoma. This second neoplasm contacted focally with the endometrial tumor. Immunohistochemical studies showed that the neoplastic endometrial glands exhibited an intense positivity for Vimentin, estrogen and progesterone receptors and cytokeratin 7. CEA was negative in this component and p16 showed only isolated positive cells. In contrast, the cervical intraepithelial neoplasm showed, both in the squamous and in the glandular component intense and diffuse positivity for p16 and CEA. In contrast, vimentin, estrogen and progesterone receptors were negative. Finally, HPV 16 was identified by PCR using the SPF10 set of primers in the endocervical adenocarcinoma but not in the endometrial tumor. Diagnosis: - Endometrial carcinoma grade 1 with squamous metaplasia involving the lower uterine segment. - CIN3 and in situ adenocarcinoma of the uterine cervix. Discussion The distinction between an endometrial and an endocervical origin of an adenocarcinoma may be difficult, especially with small biopsy specimens or when tumor is present in both endometrial and cervical specimens. Frequently these tumors show overlapping histologic features. Thus, a significant number of endocevical tumors show endometrioid features, and endometrial neoplasms frequently show mucinous differentiation. This distinction is of importance because adjuvant treatments may differ depending on whether the tumour is of endometrial or endocervical origin and the choice of primary surgery may also differ. Clues to a primary endometrial lesion include the presence of adjacent atypical endometrial hyperplasia or the presence of benign squamous elements or stromal foam cells. A primary endocervical tumour is favoured when there is adjacent CIN. Several immunohistochemical stains can be helpful in making this differentiation. The most commonly used panel of immunohistochemical stains includes vimentin, carcinoembryonic antigen (CEA) and estrogen and progesterone receptors. Most endometrial adenocarcinomas are positive for vimentin, whereas only a minority of tumors of endocervical origin are positive for this marker. CEA positivity is more common in endocervical adenocarcinomas (60-75%) than in endometrial adenocarcinomas (less than 30%). However, some endometrial adenocarcinomas may be focally positive for CEA and there is often strong positive staining of benign squamous elements. Finally ER is usually negative or there may be focal weak positivity in endocervical tumors. In contrast, endometrial adenoarcinomas usually show abundant positive cells. The p16 protein, encoded by the CDKN2A (MTS1, INK4A) tumor suppressor gene located on chromosome 9p21 decelerates the cell cycle by inactivating the function of cdk4- and cdk6-cyclin D complexes. These complexes regulate the G1 checkpoint by phosphorylation and subsequent inactivation of retinoblastoma (pRb), which releases E2F that allows the cell to enter in the S phase. In all HPV-related neoplasms, pRb has been shown to be functionally inactivated as a consequence of HPV E7 protein expression, and as a result, a strong overexpression of p16 develops. Cervical cancer and their precursor, cervical intraepithelial neoplasia and endocervical adenocarcinoma in situ, but not normal or reactive cervical epithelia, express high levels of the p16. Thus, p16 immunohistochemistry can be of help for distinguishing between an endometrial and an endocervical origin of an adenocarcinoma. Endocervical adenocarcinomas show an intense and diffuse positivity for p16 in almost 100% of cases. Most primary endocervical adenocarcinomas are characterized by strong, diffuse positivity of 100% of cells with p16. Endometrial adenocarcinomas are usually positive, but positivity is generally focal and commonly involves <50% of cells. Thus, diffuse, strong positivity with p16 suggests an endocervical rather than an endometrial origin of an adenocarcinoma. When there is morphological doubt this antibody may be of value as part of a panel for ascertaining the origin of an adenocarcinoma. Human papillomavirus (HPV) are recognized to play an etiologic role in cervical carcinogenesis and are detectable in almost all preinvasive and invasive cervical epithelial neoplasms. The high risk human papillomavirus (HR-HPV) types are etiologically related to the progression to cervical cancer because of the expression of their E6 and E7 oncoproteins to deregulate cell cycle proteins. Thus, techniques to identify HPV can also be used in the making this distinction because HPV sequences are constantly identified in cervical tumors and premalignant lesions using sensitive PCR techniques. Using in situ hybridization, HPV has been detected in 2/3 of cases. References Agoff SN, et al. p16INK4A expression correlates with degree of cervical neoplasia: a comparison with Ki-67 expression and detection of high-risk HPV types. Mod Pathol. 2003; 16:665-673. Ansari-Lari MA,et al Distinction of endocervical and endometrial adenocarcinomas: immunohistochemical p16 expression correlated with human papillomavirus (HPV) DNA detection. Am J Surg Pathol. 2004;28:160-7. Aoyama C, et al. Histologic and immunohistochemical characteristics of neoplastic and nonneoplastic subgroups of atypical squamous lesions of the uterine cervix. Am J Clin Pathol. 2005;123:699-706. Bose S, et al. p16(INK4A) is a surrogate biomarker for a subset of human papilloma virus-associated dysplasias of the uterine cervix as determined on the Pap smear. Diagn Cytopathol. 2005;32:21-4. Castrillon DH, et al. Distinction between endometrial and endocervical adenocarcinoma: an immunohistochemical study. Int J Gynecol Pathol. 2002;21:4-10. Dray M, et al. p16(INK4a) as a complementary marker of high-grade intraepithelial lesions of the uterine cervix. I: Experience with squamous lesions in 189 consecutive cervical biopsies. Pathology. 2005;37:112-24. Kalof AN, et al. p16INK4A immunoexpression and HPV in situ hybridization signal patterns: potential markers of high-grade cervical intraepithelial neoplasia. Am J Surg Pathol. 2005;29:674-9. Klaes R, et al. p16INK4A immunohistochemistry improves interobserver agreement in the diagnosis of cervical intraepithelial neoplasia. Am J Surg Pathol. 2002; 26:1389-1399. McCluggage WG, et al. p16 immunoreactivity may assist in the distinction between endometrial and endocervical adenocarcinoma. Int J Gynecol Pathol 2003;22:231-5 McCluggage WG. Endocervical glandular lesions: controversial aspects and ancillary techniques. J Clin Pathol 2003;56:164-73. McCluggage WG, et al. . A panel of immunohistochemical stains, including carcinoembryonic antigen, vimentin, and estrogen receptor, aids the distinction between primary endometrial and endocervical adenocarcinomas. Int J Gynecol Pathol 2002;21:11-5. Negri G, et al. p16INK4a is a useful marker for the diagnosis of adenocarcinoma of the cervix uteri and its precursors: an immunohistochemical study with immunocytochemical correlations. Am J Surg Pathol. 2003; 27:187-193. Ordi J, et al. Contribution of high risk human papillomavirus testing to the management of premalignant and malignant lesions of the uterine cervix. Med Clin (Barc). 2003; 121: 441-445. Ordi J, et al. Human Papillomavirus Load in Hybrid Capture II Assay: Does Increasing the Cutoff Improve the Test? Gynecol Oncol 2005; Staebler A et al. Hormone receptor immunohistochemistry and human papillomavirus in situ hybridization are useful for distinguishing endocervical and endometrial adenocarcinomas. Am J Surg Pathol. 2002;26:998-1006. Tringler B, et al. Evaluation of p16INK4a and pRb expression in cervical squamous and glandular neoplasia. Hum Pathol. 2004;35:689-96. von Knebel Doeberitz M. New molecular tools for efficient screening of cervical cancer. Dis Markers. 2001;17:123-8.