Mammary carcinoma in three mares

Abstract

MAMMARY tumours rarely develop in horses or other herbivores (Feldman 1929, Moulton 1990, and most reports of mammary carcinoma in the mare refer only to single cases (Schmahl 1972, Acland and Gillette 1982, Munson 1987, Foreman and others 1990. However, Seahorn and others (1992) reported mammary carcinomas in four mares. This short communication describes three cases of mammary carcinoma in mares which were diagnosed at the Faculty of Veterinary Medicine, Dublin, over a 10-year period, and confirms that the prognosis for survival is poor despite surgical resection of the affected gland.A 12-year-old, non-pregnant, non-lactating, thoroughbred mare presented with ventral oedema and a painful enlargement of the left mammary gland with an ulcerated surface which discharged purulent material. The left mammary gland was amputated and weighed 7 kg. The wound healed well. Five months later, the right mammary gland was enlarged and indurated with ulceration of the skin surface. The gland was surgically removed and weighed 2 kg. The owner reported that the mare died 10 months later but a postmortem examination was not performed.A 13-year-old, non-lactating, non-pregnant, Irish draught mare in poor condition presented with a hard painful swelling of the right mammary gland and with oedema of the ventral abdomen and hindlimbs. Prolonged antibiotic therapy was ineffective. Following examination of a fine needle aspirate, the right mammary gland was surgically removed and weighed 4 kg. Wound healing was delayed and the mare continued to lose weight. One month later, the left mammary gland was indurated, the ventral oedema was increased, and the mare was subsequently euthanased.A 15-year-old, non-lactating, thoroughbred mare, in poor condition and six months pregnant, presented with a large, painful, ulcerated mass involving both mammary glands and of two months duration. There was a marked ventral oedema and the mare walked stiffly. Following fine needle aspiration (FNA) the mare was euthanased.Haematological examination revealed a neutrophilia with moderate leucocytosis in cases 2 and 3; hyperglobulinaemia and hypoalbuminaemia were present in all three cases. Cytological examination of the fine needle aspirate from case 2 showed clusters of pleomorphic, basQphilic epithelial cells, some vacuolated with occasional prominent nucleoli (Fig 1). On FNA, case 3 showed clusters of plump basophilic epithelial cells, some of which were arranged in acinar formation. Cytoplasmic vacuolation, anisocytosis, anisonucleosis, marked chromatin clumping, nuclear moulding and large multiple nucleoli were apparent.On postmortem examination, the left superficial inguinal lymph glands in case 2 appeared markedly enlarged and a hard nodular mass extended via the left inguinal canal up into the pelvic canal. Nodular masses were located within the broad ligament of the uterus and the skeletal muscle of the inguinal canal. Case 3 presented a single large, firm mass weighing 10 kg, which obliterated the normal architecture of both glands. Cross-sect...

Mammary adenocarcinoma in a mare

“…Contrary to what occurs in dogs (HEIDRICH & RENK, 1967) and cats (REPPAS et al, 1996;KATO et al, 1998;MACEACHERN et al, 2001;HIRAYAMA et al, 2003), mammary neoplasms are uncommon in herbivores (THEILEN & MADEWELL, 1987;PRENDERGAST et al, 1999;MISDORP, 2002;HIRAYAMA et al, 2003). In equines, rare descriptions of mammary neoplasms are found in animals above 12 years of age (PRENDERGAST et al, 1999).…”

“…Possible complications include no healing of the wound and peritonitis (SEAHORN et al, 1992). Recurrence with the involvement of the other gland in cases of partial mastectomy may occur (PRENDERGAST et al, 1999). This work shows the importance of the histopathological examination in the differential diagnosis between the neoplasms and the chronic inflammation in the mammary gland of mares, as well as, to show that the cytological examination cannot detect the tumor, in case the puncture is made in areas of secondary infection.…”

“…Pain is not a sign that can be used to differentiate between mastitis and mammary neoplasms. In 29 cases of mammary tumors in mares found in the literature (SCHMAHAL, 1972;THEILEN & MADEWELL, 1987;SEAHORN et al, 1992;PRENDERGAST et al, 1999;HIRAYAMA et al, 2003), and 28 cases of acute mastitis (MCCUE & WILSON, 1989). Initially, the process can be confused with mastitis (REPPAS et al, 1996).…”

“…In equines, rare descriptions of mammary neoplasms are found in animals above 12 years of age (PRENDERGAST et al, 1999). In a study at slaughter houses in France with about 40,000 equines, 45 mammary tumors were observed (0.11%), the majority consisting of carcinomas (PRENDERGAST et al, 1999;MISDORP, 2002).…”

“…The first microscopic evaluation of the mammary biopsy did not reveal neoplastic cells, probably because the specimens were collected from an area of secondary inflammation. Differential diagnosis between mastitis and mammary neoplasms can be done through cytological evaluation; however this is a complementary procedure that does not replace histopathology as a diagnostic tool (PRENDERGAST et al, 1999). Mastectomy and regional lymphadenectomy may increase the life span of affected animals.…”