Which biomarker pair is listed among the options as a potential indicator to help differentiate tissue origin in endocervical versus endometrial lesions?

• A. GATA3 & PAX8
• B. p16 & CEA
• C. Pancytokeratin & p63
• D. Vimentin & ER

Answer: (A)

Immunohistochemical profiling uses marker patterns to infer tissue origin. PAX8 is a Müllerian lineage marker, so endometrium and endocervix commonly show PAX8 expression. GATA3 is more typical of non-Müllerian epithelia and, in this gynecologic context, tends to be expressed in endocervical-type lesions but not in most endometrial lesions. When both markers are positive, that pattern supports endocervical origin; if PAX8 is positive but GATA3 is negative, endometrial origin is more likely. The other marker pairs don’t provide as clear a distinction between endocervical and endometrial tissue: p16 and CEA are less specific for this differentiation, Pancytokeratin with p63 covers broader epithelial vs squamous differentiation, and Vimentin with ER relates more to mesenchymal versus hormone receptor status rather than pinpointing endocervical versus endometrial origin.