An ovarian interstitial cell hamartoma in a newborn foal.

This research documents a rare case study of a newborn, thoroughbred foal who was found to have a congenital ovarian interstitial cell hamartoma, a benign tumor, which was discovered post-mortem.

Clinical Presentation and Findings

• The newborn foal, belonging to the thoroughbred breed, died after 14 hours of birth mainly due to an apparent nutritional muscle disease, termed as white-muscle disease. This disease typically affects the skeletal muscles and heart of newborn animals, resulting from deficiency of vitamin E and selenium.
• However, during the necropsy it was observed that there was an incidental finding of a strange, mushroom-shaped mass that was pale brown in color and had swollen out of the foal’s left ovary. The mass turned out to be a pedunculated ovary, which is a form of ovary that has an elongated stalk. The dimensions of this mass were noted to be 6 x 4 x 3 cm.

Examination of Tumor

• The mass was dissected for further examination and it was observed that it had a peripheral rim made of a dense tissue parenchyma, which is the functional tissues in an organ. This rim was kept aside and was around 3-5 mm wide. The center of the mass was filled with a pale, gelatinous substance.
• The mass was viewed under a microscope for histological examination. In histology, tissues are examined under microscope to study the manifestations of disease. The mass was found to consist of a densely packed layer of large cells at the periphery, which showed strong similarities in morphology with the foal’s fetal ovarian interstitial cells.
• In the central portion of the cut mass, there were small nests of similar cells, but these were scattered within an extremely loose connective tissue matrix instead of being densely packed as in the periphery.
• Subsequently, the researchers conducted an immunohistochemistry analysis. In immunohistochemistry, the presence of certain proteins in the tissues is detected through the use of antibodies. The analysis revealed positive labelling for inhibin within the cells’ cytoplasm. Inhibin is a hormone which regulates the production of follicle-stimulating hormone in the body intricately associated with ovarian functions.

Final Diagnosis

• Based on the observations of the histological and immunohistochemical analyses, the researchers concluded that the lesion present in the foal was indeed an ovarian interstitial cell hamartoma.
• Hamartoma is a benign tumor-like formation, that grows in an organ but is made up of tissue that is normal to that organ.