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
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Issue 2018
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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.