Vet360 Vet360 Vol 05 Issue 04 - Page 28

DENTISTRY The Oncept Canine Melanoma Vaccine, DNA (Merial), is administered in stages II and III of canine oral melanoma and can decrease recurrence in some cases after removal or debulking of the primary tumor. The glycoprotein tyrosinase, which produces melanin found in melanoma cells, is the vaccine’s targeted antigen. The vaccine appears to be effective in cases of amelanotic melanoma too. In a 2016 study that retrospectively reviewed the outcome and survival of 32 dogs affected by oral melanoma that were treated with a combination of surgery and the xenogeneic DNA vaccination (with the addition of radiotherapy in some cases), the overall median survival time was 335 days, and the overall median progression- free survival (PFS) was 160 days. 1 Disease stage, surgical margin completeness and vaccine administration delay did not appear to statistically influence survival or PFS, though these results may reflect the study’s low statistical power due to small numbers. Squamous cell carcinoma. Like malignant melanoma, squamous cell carcinoma is a locally aggressive tumor (Figure 2). Oral squamous cell carcinoma in dogs rarely metastasizes unless it affects the tongue or tonsil, and when it does, abdominal ultrasound is indicated as part of staging because distant metastasis is more common to the liver and spleen than to the lungs. Oral Malignancy Nomenclature Adenocarcinoma: An invasive, malignant epithelial neoplasm derived from glandular tissue of either the oral cavity, nasal cavity or salivary tissue (major or accessory) with moderate metastatic potential. Anaplastic neoplasm: A malignant neoplasm with cells that poorly resemble the normal histologic differentiation pattern; also called a poorly differentiated neoplasm. Fibrosarcoma: An invasive, malignant mesenchymal neoplasm of fibroblasts with a low metastatic rate; a distinct histologically low-grade, biologically high-grade variant is often found in the oral cavity. Haemangiosarcoma: A malignant neoplasm of vascular endothelial origin characterised by extensive metastasis; has been reported in the gingiva, tongue and hard palate. Lymphosarcoma: A malignant neoplasm defined by a proliferation of lymphocytes within solid organs such as the lymph nodes, tonsils, bone marrow, liver and spleen; the disease may also occur in the eye, skin, nasal cavity, oral cavity and gastrointestinal tract; also known as lymphoma. Malignant melanoma: An invasive, malignant neoplasm of melanocytes or melanocyte precursors that can be pigmented or amelanotic, with a marked tendency to metastasize. Figure 2. Papillary squamous cell carcinoma in a young dog. Surgical excision is the primary treatment of choice for macroscopic oral squamous cell carcinoma in dogs, followed by radiation therapy for microscopic disease. Local recurrence is common. Piroxicam, a nonsteroidal anti-inflammatory (NSAID) agent given orally at a dosage of 0.3 mg/kg every other day, can be used for palliation with a median survival time of 180 days in dogs in one monotherapy study. 2 A slightly higher median survival time (272 days) was achieved when piroxicam was combined with cisplatin or carboplatin. 3 A recent study of 87 dogs affected by nonmelanotic oral malignancies revealed that dogs undergoing postoperative radiotherapy after incomplete excision of oral squamous cell carcinomas had a significantly longer mean survival time (2,051 days) than dogs with incompletely excised tumors and no radiotherapy (181 days). 4 vet360 Issue 04 | SEPTEMBER 28 Issue 2018 04 | | AUGUST 2017 28 Multilobular tumor of bone: A locally invasive and potentially malignant neoplasm of bone more commonly affecting the mandible, hard palate and flat bones of the cranium, with a multilobular histological pattern of bony or cartilaginous matrix, surrounded by a thin layer of spindle cells that gives it a near-pathognomonic popcorn-ball appearance on radiographs; also called multilobular osteochondrosarcoma, multilobular osteoma, multilobular chondroma, chondroma rodens and multilobular osteosarcoma. Osteosarcoma: A locally aggressive, malignant mesenchymal neoplasm of primitive bone cells that have the ability to produce osteoid or immature bone with a high metastatic rate. Squamous cell carcinoma: An invasive, malignant neoplasm of the oral epithelium with varying degrees of squamous differentiation; tonsillar squamous cell carcinoma has a higher metastatic rate and poorer prognosis than nontonsillar squamous cell carcinoma.