Lymphangiosarcomas are aggressive, rare malignant tumours that originate in the endothelial cells of the lymphatic vessels. In veterinary medicine they have been reported in dogs, cats, horses, a cow and an Asian otter. A study has now reported a possible first case in a rat.
An adult intact female rat (Rattus norvegicus) was presented with a non-painful, hard subcutaneous mass on the left axila. A physical examination and blood test values were within the normal range.
Following surgery, the mass was sent for histopathological analysis. The presence of a lymphangiosarcoma was confirmed, so metronomic chemotherapy with toracenib, a tyrosine kinase inhibitor, was delivered.
Three months later, two new masses appeared: one in the left chest and other in the inguinal area. Aside from these masses the physical examination was unremarkable. Histopathology revealed that the mass in the chest was a lymphangiosarcoma while the inguinal mass was a mammary fibroadenoma.
Six months later the animal died as a result of an unexpected acute gastrointestinal condition. A necropsy was not carried out, and without having metastasis reported, we cannot rule out the possibility that this had taken place or that the rat had other concurrent health problems.
Recurrence is common in this type of neoplasm as margins are difficult to achieve. In this case, a new and similar tumour was identified three months after the first surgery. Given the average life span of rats if 2-3,5 years, this is a long period. The case highlights the necessity of including lymphangiosarcomas in the differential diagnosis list of subcutaneous masses in rats. More research is required to study its prevalence and explore possible predisposing factors for the condition.
Soler V. et al. Subcutaneous lymphangiosarcoma in a pet rat (Rattus norvegicus). Journal of Exotic Pet Medicine (2019) 28-31. https://doi.org/10.1053/j.jepm.2019.06.003
