Uterine tumours are not very frequent in either bitches or queens. The reported frequency in the bitch is between 0.3 and 0.4% of all canine tumours. In a study carried out in a population of 75,000 dogs, of which 3,073 with cancer, only 11 had a uterine tumour (10 leiomyomas and 1 leiomyosarcoma). In the cat, uterine tumours account for 1-2% of female reproductive tract tumours and 0.2-1.5% of all feline tumours.
SIGNALMENT AND HISTORY
Uterine tumours are more common in elderly bitches (over 10 years old) and although no breed predisposition has been shown, in the German shepherd there is an hereditary neoplastic syndrome characterized by the presence of bilateral, multifocal renal cystoadenocarcinomas, nodular dermatofibrosis and, in 80-90% of cases, multiple uterine leiomyomas. In the queen, the few cases described in the literature occurred in subjects between 4 and 15 years old; two reported cases involved pedigree cats (Siamese and Persian), although this is no evidence of a breed predisposition.
BIOLOGICAL BEHAVIOUR
In both the bitch and the queen, the uterus may be the site of primary tumours or the site of metastases from ovarian or mammary tumours or lymphoma. Both benign and malignant primary tumours have been reported; in general terms epithelial neoplasms are usually malignant, while mesenchymal neoplasms are benign; the tumours can involve the broad ligament, the myometrium or the endometrium.
Benign uterine tumours include leiomyoma (by far the most frequent), fibroleiomyoma, fibroma, fibromyoma, fibroadenoma, adenoma, lipoma and endometrial polyps. Leiomyomas are often an incidental finding during a post-mortem examination or ovariohysterectomy and apparently do not even interfere with pregnancy. Endometrial polyps are benign, focal, cystic formations deriving from the proliferation of endometrial glands. Leiomyomas are usually non-invasive, non-metastasising and slow growing; they can be pedunculated or sessile, broad-based, and can project into the uterine lumen, thus becoming visible on an ultrasound examination. One case of benign intramural angiolipoleiomyoma and one case of bilateral diffuse haemangiosarcoma with invasion of the ovaries and broad ligament have been reported in bitches. The broad ligament can be affected by lipomas, which appear as spherical or ovoid, pedunculated formations, usually of 2-4 cm in size, although a large lipoma (25x16x7 cm) has been reported.
Malignant uterine tumours include leiomyosarcoma, adenocarcinoma, endometrial carcinoma, lymphosarcoma and metastases of transmissible venereal tumour and ovarian disgerminomas. Leiomyosarcomas are invasive and metastasise slowly. Uterine carcinomas are extremely rare in the bitch (no case reported in a series of 6,000 canine tumours), and in the few cases of uterine adenocarcinomas described, an iatrogenic cause has been considered possible (exposure to radiation prior to 1 year of age and treatment with oestrogens-progestogens). Uterine adenocarcinomas are usually single, solid or cystic, sessile or pedunculated; they obliterate the uterine lumen and at the time of diagnosis may have already metastasised to the brain, eyes, lungs, pericardium, myocardium, thyroid gland, diaphragm, adrenal glands, liver, ovaries and kidneys or to regional lymph nodes.
The following tumours have been reported in the queen: adenoma, adenocarcinoma, leiomyoma (this last with a lower frequency than in bitches and often multiple), leiomyosarcoma, carcinosarcoma, fibroma, papillary adenocarcinoma and squamous cell carcinoma, probably in the form of metastatic disease of cervical origin. Based on the few cases reported, however, it appears that in the queen there is a higher prevalence of adenocarcinomas, which are usually invasive and metastasise to the parietal and visceral peritoneum, omentum, diaphragm, lungs, ovaries, bladder, colon, brain and eyes.
SIGNS AND DIAGNOSIS
Given that in many cases uterine tumours are an incidental finding, bitches are generally asymptomatic and the clinical examination does not reveal any abnormality. In the case of benign tumours, symptoms become evident when the neoplastic mass expands to a considerable size and compresses various abdominal organs, most frequently those of the urinary and gastrointestinal systems, with consequent urethral and rectal tenesmus or occlusion of the pelvic canal. Although infrequently, these tumours can be accompanied by alterations in the menstrual cycle and a variable degree of vaginal discharge.
Bitches affected by adenocarcinoma may have the typical signs of advanced neoplastic disease and of any concomitant cystic endometrial hyperplasia/pyometra. The signs can, therefore, be extremely varied and may include a persistent haemorrhagic or purulent vulvar discharge, fever, lethargy, anorexia, vomiting, polydipsia and polyuria, dysuria, haematuria, worsening of overall conditions, dyspnoea and abdominal distension. Other signs depend on the site of any metastases. Cases of blindness and neurological symptoms have been reported in queens with uterine adenocarcinoma which metastasised to the brain and eyes.
Trans-abdominal palpation and, in some cases, also rectal digital palpation, can detect the tumour if it is particularly large (Fig. 1), while vaginal digital exploration does not give any clinical indication. In the case of metastases to the sub-lumbar lymph nodes, palpation can detect enlarged, asymmetrical lymph nodes. Radiographic and ultrasound examinations may confirm the uterine involvement. Although ultrasonography enables better identification of the exact location of the tumour within the uterus and the extension of the tumour, echogenicity is not informative, as it is quite variable in these tumours. The final diagnosis is, therefore, based on histological examination, done on a needle biopsy obtained under ultrasound guidance or on a specimen taken during surgical excision (Figs. 2 and 3) and ovariohysterectomy. Both ultrasonography and radiographic examinations are indispensable to look for any metastases.
In the bitch, trans-cervicalneedle biopsyofendometrial tissue can be used to assess various physiological and pathological states; however, its usefulness in the diagnosis of uterine tumours has not yet been adequately studied. The Tumour, Node, Metastasis (TNM) staging system requires the collection of clinical and post-surgical information on the tumour, the assessment of sub-lumbar regional lymph nodes, together with chest X-rays, and information deriving from imaging studies (nuclear magnetic resonance, computed tomography, abdominal ultrasound).
TREATMENT
The treatment of uterine tumours is based on ovariohysterectomy (Fig. 4), following staging of the patient. Scientific information on the possible usefulness of chemotherapy and radiotherapy are not yet conclusive.
PROGNOSIS
The prognosis of patients with benign tumours is good, but depends on excision of the neoplasm, as its slow but continuous increase in volume may lead to compression or obstruction of various abdominal organs, particularly those of the urinary and digestive systems. The prognosis of patients with malignant tumours depends on the histotype, on the degree of local invasiveness and on the presence of metastases, and is usually guarded in adenocarcinomas, given their potential to metastasise rapidly.
Suggested readings
- Argyle DJ, Brearley MJ, Turek MM (2008) Tumors of the female genital tract. In: Decision making in small animal oncology, Blackwell, Ames: 315-318.
- Klein MK (2007) Tumors of the female reproductive system. In: Withrow SJ, Vail D. Withrow and MacEwen’s small animal clinical oncology. Saunders, S.Louis: 610-618.
- JohnstonSD, Root Kustritz MV, Olson PNS (2001) Disorders of the feline uterus and uterine tubes (oviducts). In: Canine and Feline Theriogenology. Saunders 3rd ed Philadelphia: 463-471.
- JohnstonSD, Root Kustritz MV, Olson PNS (2001) Disorders of the canine uterus and uterine tubes (oviducts). In: Canine and Feline Theriogenology. Saunders 3rd ed Philadelphia: 206-224.
- Morris J, Dobson JM (2001) Genital tract. In: Small animal oncology, Blackwell, Oxford: 166-174.
- McEntee MC (2002) Reproductive oncology. Clin Tech Small Anim Pract,17: 133-149.
- Hedlund CS (2004) Chirurgia dell’apparato genitale e riproduttore. Neoplasie dell’utero In: Fossum TW Chirurgia dei piccoli animali. Masson/Ev, Milano, Cremona 2nd ed.: 623-624.