Multiple Uterine Subserosal and Submucosal Intramural Leiomyomas in a Mare: An Immunohistochemical Study

Highlights

• A rare uterine leiomyoma was detected in a 32 years old, pluriparous, oriental horse breeds, mare.

• Tissue changes are described with particular emphasis to immunohistochemical patterns.

• A diffuse cytoplasmic reactivity for smooth muscle actin was revealed by immunohistochemistry.

• Vimentin was encountered in focal areas of fibrosis and in the wall of vessels, typical for leiomyoma.

Abstract

A 32-year-old, pluriparous, oriental horse breed mare was presented to the Veterinary Teaching Hospital of the Veterinary Medical School of Messina, with clinical symptoms characterized by vulvar blood drainage for suspicious abortion. Ultrasonographic examination showed the presence of blood in uterine body and a complex-mass structure, echo dense with cystic areas with anechoic content at the basis of the right horn. Uterine leiomyoma was suspected, a partial ovary hysterectomy was proposed to the owner; despite this, the owner refused to submit the mare to surgery. The mare spontaneously died after 18 months, and necropsy was performed. At macroscopic postmortem examination, the right uterine horn showed a well-demarcated pedunculated nodular bulge, variegated in color with large hemorrhages (22 × 18 × 15 cm), and a capsulated sessile nodule (7 × 4 × 3 cm) involving the smooth uterine musculature. Histologic analysis suggested a diagnosis of subserosal leiomyoma (large mass) and submucosal intramural leiomyoma (small nodule).

Introduction

Uterine tumors are rarely detected in domestic animals. Only the 0.4%–1.6% of the neoplasms diagnosed in equine species have a uterine origin [1]. Moreover, several kinds of tumors have been reported as incidental uterine findings in horse, such as fibroma, fibrosarcoma, adenocarcinoma, lymphosarcoma, leiomyoma, leiomyosarcoma, fibroleiomyoma, and rhabdomyosarcoma [1]. Leiomyoma is a benign neoplasm derived from the external smooth muscle of the uterus. This neoplasm seems to be the uterine tumor more frequently reported in mares [2]. In mares, uterine leiomyomas are generally benign and pedunculated, even if they could also appear as intramural masses [3]. Small uterine tumors (<5 cm) can be hard to find and/or could be an incidental finding during clinical evaluation; very often, they are clinically asymptomatic. Uterine neoplasms of bigger size (>5 cm) are commonly associated to clinical signs, such as persistent infertility, abdominal pain, protrusion of the neoplastic tissue through vulva, recurrent uterine hemorrhage, and secondary endometritis. Furthermore, they can be palpable via transrectal inspection or detected at ultrasound examination during a clinical evaluation of the genital system of mares with hypofertility or via hysteroscopy [3], [4], [5], [6], [7]. These benign neoplasms may interfere with fertility and consequently should be surgically removed as an elective treatment choice, determined by size and localization of the tumor; by contrast, malignant tumors are generally not eligible to treatment because of their usually poor prognosis. However, in cases of very large and extremely invasive tumors, complete or partial ovary hysterectomy has been generally suggested [3]. Considering that only few sporadic data about multiple uterine leiomyomas are present in literature on mares, we would describe herein a case report concerning the occurrence of this unusual pathology in an old mare.