ABSTRACT

Uterine tumours in the bitch are considered rare. The most common are leiomyomas representing more than the 90% of all uterine canine tumours. Very few cases of uterine malignant tumours have been described in the veterinary literature and uterine liposarcoma had never discovered. Also in human medicine lipomatous tumours, whether benign or malignant, are very rare in the uterus. These tumours may arise from the misplacement of an embryonic progenitor cell, metaplasia of mature mesenchymal tissues of other types, perivascular adipocytes or from traumatic displacement of adipocytes. The authors describe a case of unilateral liposarcoma in the uterus of a German Shepherd dog and its radiographic, ultrasonographic evaluation and the histopathological appearance.

1. Introduction

Liposarcomas are rare malignant tumours of white adipose cell lipoblasts [1]. They are considered a soft tissue neoplasm because of their mesenchymal or connective tissue cell origin. They often arise from the skin and subcutis [2]. Most reports indicate that liposarcomas are unlikely to metastasize; however, a few published reports suggest that liposarcomas are aggressive, locally invasive, and commonly metastasize to the lungs, liver, and bone [3].

Uterine tumours in the bitch are considered rare, accounting for only 0.4% of all canine tumours, and between 1% to 19% of all the female genital tract tumours [3-5]. The most common are leiomyomas representing more than the 90% of all uterine canine tumours [1]. It is thought that steroid hormones play a role in the pathogenesis of leiomyomas [2]. However, malignant tumour diseases in dogs are extremely rare with very few cases described in the veterinary literature [6].

Tumours of the canine genital system are usually detected during necroscopy or ovariohysterectomy [7,8]. Clinical signs are dependant on the size and location of the tumour. Sometimes there are no consistent clinical signs to indicate cancer involvement in the uterus other than the presence of an abdominal enlargement that can be revealed by a physical examination [3].

In this study, clinicopathological and immunohistochemical findings of canine unilateral liposarcoma were described.

2. Case Report

A 10 years old German Shepard bitch was brought to the Veterinary Teaching Hospital of the University of Camerino for history of intermittent inappetence. On physical examination a localised left caudodorsal bulging was noted and on palpation an abdominal mass discovered. The mass appear to be quite firm and extended from the third to seventh intervertebral space. Abdomen radiographic examination in a right lateral view was performed. Radiographic finding was indicative of a large and not well-defined mass, with mixed soft tissue opacity and irregular marginated (Figure 1).

Realtime B mode ultrasonography equipment (Esaote, Mylab 30 Vet) was used with 5 - 8 MHz microconvex probe in order to perform an abdominal examination. Dorsal to the urinary bladder, just cranial to the uterine bifurcation a well marginated mass was noted. The mass appeared to be eterogeneus in ecotexture for the presence of multiple cyst like lesion mixed with areas of hypoecogenicity (Figure 2). On the colour Doppler examination the mass showed no internal colour flow and a very feeble colour contour outside the capsule. All the other organs were within normal limits.

In order to see if thoracic metastasis were present

right-lateral thoracic radiograph was done and no abnormality was detected.

Prior the surgery a complete serum haematology and biochemistry were performed.

The dog was premedicated with 5 µg/kg intramuscular medetomidine and 0.3 mg/kg intramuscular tramadol. Anaesthesia was induced with 2 mg/kg intravenous propofol and general anaesthesia was maintained with isoflurane in oxygen.

An exploratory laparotomy was performed via a midline incision and an irregular-shaped, firm mass, 21 × 17 × 12 cm in size, was identified in the uterine left horn.

Ovariohysterectomy was performed to remove the mass (Figure 3). Recovery of the bitch was rapid and uneventful. Samples of the mass were fixed in 10% buffered formalin and subjected to routine histopathological evaluation.

With E-E staining, the neoplastic tissue appeared costituited by relatively mature adipocytes with a single clear fat vacuole and a peripheral oval nucleus or with cytoplasm containig variably sized lipid droplets and round nucleus (Figure 4). The size of neoplastic cells were variable and in a proportion of cells, atypical and hyperchromatic nuclei were found. Admixed with these cells are scattered bizarre, often multinucleate, stromal cells and variably prominent fibrous septa containing hyperchromatic spindle cells and occasional bizarre cells.

For immunohistochemical investigations, 3 μm-sections were cut from each specimen and labelled for the presence of Vimentin, pancytokeratin (CK), S-100 and Ki-67 antigens (Dako Corporation, Carpinteria, CA, USA). Immunohistochemical reaction was detected using an avidinbiotin-peroxidase method according to manufacturer’s instructions (Vector Laboratories, Inc., Burlingame, CA, USA). A solution of 25 mg of 3-3’diaminobenzidine (DAB) was used as the chromogen while nuclear counterstaining was performed with Mayer’s haematoxylin.

Immunohistochemically, the neoplastic cells were vimentin-positive and CK-negative (Figures 5 and 6).

The proportion of labelled cells with anti-Ki-67 antibody varied from 26% to almost 75% and the intensity varied from moderate to intense. An occasional positivity to S-100 antigen was found (Figure 7).

3. Discussion

Liposarcoma, malignant counterpart to the lipoma, is rare in domestic animals, probably most common in the canine species. It is a typical tumour of the skin and soft tissues. There is no sex predisposition but the incidence increases with age [9].

Very few cases of uterine malignant tumours have been described in the veterinary literature [6,10-13] and uterine liposarcoma was never discovered.

Being the most massive overgrowth was not possible

to properly display the genital tract, making it uncom-

fortable identifying the exact origin of it. The exploratory laparotomy was performed to identify the relevance of the uterine mass.

Excision of the mass associated with ovariohysterectomy has proven therapy of choice as a decisive and uncomplicated. Given the size of the mass, we evaluated the uterine liposarcoma of the dog is likely to slow tumour growth and with little tendency to metastasis.

To the author’s knowledge, this is the first case of a uterine liposarcoma in a bitch.

REFERENCES