Clinical Case Challenge

Figure 2

Figure 2

History: A 6-year-old female spayed Lionhead rabbit presented to Tufts Foster Hospital for Small Animals with a one-day history of inappetance. She also had a recent history of urine scald. On physical examination the rabbit was noted to be overweight with increased subcutaneous and abdominal fat stores. The results of a complete blood count revealed a leukocytosis (26.2 x 103cells/µl; reference range, 5 – 12 x 103cells/µl) with a lymphocytosis (23.4 x 103cells/µl; reference range, 1.25 – 6 x 103cells/µl). Continue reading

Current Concepts

Thymoma in Rabbits

Rabbits normally have a large thymus that is placed cranial to the heart and extends into the thoracic inlet. Thymoma, thymic lymphoma and thymic carcinoma have all been reported in rabbits. Thymic lymphoma and carcinoma are rare in rabbits.The overall incidence of thymoma in rabbits is low (around 7% of reported neoplasms in 55 colony rabbits) with no apparent sex predilection. The mean age at presentation is 6.7 years based on one survey of 19 cases. Rabbit thymomas are generally slow growing and are potentially locally invasive tumors that rarely metastasize. Continue reading

Current Concepts

Oral Malignant Melanoma in Dogs and Cats

Melanoma is a tumor of melanocytes, which arise from neural crest cells and function to synthesize melanin. Melanocytes are commonly located in the oral cavity, haired skin and eye, making these the most common locations where melanomas arise. Biologic behavior of melanoma depends in part on tumor location. The majority of melanomas that arise in the oral cavity are classified both histologically and biologically as malignant. Histologic features that support a diagnosis of oral malignant melanoma include a mitotic index greater than 2 mitoses per 10 high-powered fields, nuclear atypia, vascular or lymphatic invasion and ulceration. Malignant tumors may be variably pigmented or amelanotic (one third of cases). Since melanocytes are derived from neural crest cells, which ultimately give rise to both glandular tissues and connective tissues, melanomas can resemble both carcinomas and sarcomas morphologically. Given these challenges to diagnosing a malignant melanoma, several immunohistochemical stains have been developed to aid in the diagnosis.  Melanomas typically stain positive for vimentin, melan A, S100, and neuron-specific enolase (NSE); these stains can be helpful in diagnosis. Continue reading

Innovation

Hypofractionated radiation therapy combined with the ONCEPT canine melanoma vaccine for canine oral melanoma

The Veterinary Radiation Therapy Oncology Group consists of a group of board-certified radiation oncologists across the nation dedicated to cooperative clinical trials to improve the survival of animals with cancer. The team at Tufts’ Foster Hospital for Small Animals is part of this consortium and is currently enrolling patients.  This organization is currently conducting an independent study to evaluate the treatment of canine oral malignant melanoma with coarse-fraction radiotherapy (8 Gy for 4 weekly fractions) in combination with the ONCEPT™ melanoma vaccine. Data for three treatment groups (concurrent radiation therapy and vaccine; radiation therapy alone; vaccine alone) will be collected.  Given that the study is not funded, treatment selection will be based on owners preference.  The primary objective of this study is to compare tumor progression between the treatment groups with a secondary objective of evaluating overall survival time. Continue reading