After imaging, ovaries were fixed in Bouin’s solution for 2 to 4 h, transferred to 70% ethanol, dehydrated, embedded in paraffin blocks, and sectioned at 5 μm thickness. Orientation was carefully maintained from explant to imaging, fixation, paraffin embedding, and sectioning, by maintaining anatomical orientation at explant and placing the ovary face up on filter paper indicating medial-lateral and superior-inferior locations. Histology sections were taken perpendicular to the area imaged, allowing a cross-sectional view of the imaged edge. Every 20th section was mounted and stained with hematoxylin and eosin. All histologic specimens were evaluated by a pathologist and a gynecologic oncologist with veterinary training. Any ovary with suspected tumor had additional sections immunostained with cytokeratin (anti-cytokeratin 18 antibody [E431-1] and rabbit polyclonal to wide-spectrum cytokeratin, Abcam Inc., Cambridge, MA), per the manufacturer’s recommended protocol, to determine if the tumor was of epithelial origin. The specimens were diagnosed per pathologic findings into the following seven categories: normal, DMBA-effect, tubular adenoma, tubular adenoma with areas of focal dysplasia, granulosa cell tumor, Sertoli–Leydig cell tumor, or adenocarcinoma. Normal ovaries were those which contained only healthy tissue or changes consistent with a normal aging process. DMBA-effect was a benign abnormality, caused by DMBA exposure, characterized by epithelial cell proliferation, degenerating follicles, degenerating corpora lutea, and highly active steroidogenic cells. Tubular adenoma was a benign epithelial tumor of glandular origin characterized by cells organized in tubules. The limited number of granulosa cell and Seroli–Leydig cell tumors seen precluded their inclusion in the image analysis. Adenocarcinoma, a malignant tumor arising from the epithelial cells of glandular tissue, is the most common form of ovarian cancer in women.