CXCL12 expression in healthy and malignant ovaries. (A) Healthy ovary (i), CXCL12 immunoreactivity in OSE (inset is the outlined region on the tissue specimen containing surface epithelium, × 40), faint staining in the stroma and no signal in follicles and oocytes (arrow) (× 20); fallopian tube (ii), CXCL12 immunoreactivity in cells of the epithelium (× 40). (B) Serous (i) and mucinous (ii) benign epithelial ovarian tumors, CXCL12 immunoreactivity in proliferating epithelial cells (× 40). (C) Serous (i and iii) and mucinous (ii and iv) borderline epithelial ovarian tumors with low (CXCL12low, i and ii) or high (CXCL12high, iii and iv) levels of CXCL12 staining (× 40). (D) Malignant epithelial ovarian tumors: serous (i), mucinous (ii), clear-cell (iii) and endometrioid (iv), CXCL12 immunoreactivity in epithelial cells is confined to the cytoplasm, with frequent strong staining of the membrane (arrows), no staining in the nuclei of tumor cells or in the stroma (× 40). (E) Cytocentrifuged CD326+ epithelial (i) and CD326- non epithelial (ii) cells isolated from malignant ascites collected from a patient diagnosed with invasive EOC, CXCL12 is detected only in CD326+ cells (× 40). (F) Non epithelial ovarian tumors: granulosa tumor (i) and dysgerminoma with characteristic morphological features, i.e. Exner bodies (arrow) (ii), absence of CXCL12 immunostaining from both tumors (× 40). No labeling was detected when the K15C anti-CXCL12 mAb was omitted or a 100-fold molar excess of recombinant CXCL12 was added to the mAb before incubation with tissues.