Localization of S1P1 receptor protein expression in hen ovarian tumors. (A) An example of a mucinous ovarian tumor with S1P1+ staining associated with surface epithelium (black arrow) and mucin-secreting structures (black arrow) (100×). (B) H& E stained section (100×) serial to that in (A) shows mucinous histology. (C) Higher magnification of (A) showing S1P1+ mucin-secreting glandular (MG) structures (black arrows) (400×). (D) H&E stained section of a serous ovarian tumor (100×). (E) Serial section showing minimal stromal cell stain for S1P1+ but intense surface epithelial cell staining (black arrow) and lighter more diffuse S1P1+ sub-epithelial cells (white arrow) (100×). (F) High magnification (of box) showing S1P1+ surface epithelial cells (EpC) (600×). (G) Clear-cell ovarian tumor (T; left of dotted red line) with negligible S1P1+ in tumor and S1P1+ cells in adjacent uninvolved stroma (100×). (H) H&E-stained serial section from the same tumor region in (G) shows cellular detail of clear cell carcinoma (400×). (I) Higher magnification of box in(G) showing stromal blood vessels (BV) with S1P1+ endothelial cells and stromal cells (S) (200×). (J) H&E stained section of late stage endometrioid tumor (100×). (K) S1P1+ is highly expressed in cells in the tumor periphery and to a lesser extent in tumor stroma (100×). (L) High magnification of box in (K) showing cytoplasmic staining of endometrioid tumor cells (400x). All images are from paraffin-embedded tissue, except clear cell carcinoma (G-I) which is a frozen section.