OVARIAN FIBROTHECOMA IN A SACHSEN WARMBLOOD MARE

Nowadays in human medicine the term “fibrothecoma or fibrosed thecoma” is used to describe a rare benign ovarian neoplasm with gonadal stromal cell origin belonging to thecoma-fibroma group. (1, 2). The fibrothecoma is formed by collagen producing fibroblasts, in addition to theca cells containing lipids (3). In mare this tumor is rare and to date only three cases have been reported (4, 5, 6). A 18-year-old Sachsen Warmblood mare was presented to the Veterinary Teaching Hospital of Camerino University, with a history of infertility. Rectal palpation and ultrasonography examinations revealed an enlarged right ovary with an anechoic cyst cavity (10-12 cm), surrounded by a thick and hyperechoic wall measuring 1-2-cm, no evidence of follicular activity was observed. An ovarian tumor was suspected and surgical excision of the ovary was performed. Grossly the ovary was totally occupied by a large mass, with whitish, irregular and lobulated surface measuring 21x13x12 cm. On cut surface a solid thick wall with white-yellowish bands circumscribing a large central cystic area was observed. Tissue specimens were submitted for histopathological examination and immunohistochemical analysis using antibodies to vimentin, alpha-smooth muscle actin (α-sma), inhibin, CD99, CD117, MIB1, S100. Histologically the ovary was totally effaced by a densely cellular neoplasm composed of spindle cells with oval or spindle-shaped nuclei, arranged in interlacing bundles on a fibrous stroma. Multifocally neoplastic cells had lipid vacuoles within cytoplasm, a feature consistent with thecal differentiation. Anisocytosis and anisokaryosis were mild. Immunohistochemistry revealed a strong and diffuse staining of neoplastic cells for vimentin and a multifocal positivity for α-sma, as observed in two other studies in mare (4, 5). Multifocally neoplastic cells had strong positive immunolabeling for inhibin, a sex cord-stromal marker not evaluated in the other studies in mare. Negative staining for CD99, CD117 and S100 was noted and ki67 proliferation rate was low. The histopathological and immunohistochemical findings of this rare ovarian neoplasm are consistent with a fibrothecoma and our results are similar to those found in the few reported cases in mare. The expression of inhibin observed in this case demonstrated that tumor was hormonally productive, a status associated with infertility problems. 1. Scully R and Sobin L. Histological Typing of Ovarian Tumours, vol. 9. Springer: New York, Berlin, 1999. 2. Kurman R. 1994. Blaustein’s Pathology of the Female Genital Tract. Springer-Verlag: New York. 3. Chen VW et al. 2003. Pathology and classification of ovarian tumors. Cancer Suppl; 97: 2631– 2642. 4. Firat I. and Sönmez K. 2011. Fibrothecoma in A Trough Bred Mare with Unilateral Ovariectomy: A Case Report. Kafkas Univ Vet Fak Derg 17, 329-332. 5. Kievitsbosch T et al. 2013. Ovarian Fibrothecoma in Mare-Case Report. Journal of Equine Veterinary Science 33, 813-819 6. Azizi S. et al. 2014. Ovarian Fibrothecoma in an Arabian Mare: A Rare Case Journal of Equine Veterinary Science 34, 314–317.