Pulse - March 2022 - 16

PRACTICAL PATHOLOGY
Mandibular Neuroectodermal
Tumor in a Dog
Farshid Shahriar DVM, PhD, Dipl ACVP - Lore Laboratory, Tustin, CA
Young Joo Kim, DVM - Central Orange County Emergency Animal Hospital, Newport Beach, CA
Medical history and clinical findings:
Right mandibulectomy of a 11-year-old, male-neutered Golden Retriever dog was performed.
A raised, approximately 2.5x2x1.8 cm bone growth at mid mandible and at the
level of 308 was observed and examined histologically.
Histopathologic findings:
There is invasion of the bone by a malignant small round blue cell neoplasm composed
predominantly of densely packed round neoplastic cells subdivided into nonorganoid nests
by trabeculae of fine fibrovascular stroma (Fig. 1, 2). Tumor cells have small round vesiculated
nuclei and scant amounts of amphophilic cytoplasm with mild anisonucleosis. Foci
of tumor cells form rosettes and line up around poorly formed lumens of somewhat tubular
and glomeruloid structures (Fig.3) . Mesenchymal differentiation is not observed and
there is no chondroid or osseous or squamous or odontogenic differentiation. There are
3 mitotic figures/10hpfs. Multifocal, severe, acute caseous necrosis and chronic recurrent
hemorrhage is present with scattered hemosiderin laden macrophages. There is multifocal,
moderate, chronic, histiocytic inflammation in response to tumor necrosis. There is
no invasion of the salivary glands in the sections examined by tumor cells. No organisms,
teeth, keratin, dentin, osteoid, striations, strap cells or foreign bodies are seen.
Diagnosis:
Diagnosis of a malignant neoplasm with features of a primitive neuroectodermal tumor
was made.
Discussion:
This tumor exhibits features suggestive of a primitive neuroectodermal tumor (PNET)
which may be primary intraosseous or less likely arising from the large nerve in this
specimen. PNET are rare neuroendocrine tumors that arise from primitive cells of the
embryonic neural tube. Central primitive neuroectodermal tumors arise in the brain
or spinal cord while neuroblastomas arise in the Autonomic nervous system in various
sites throughout the body and peripheral primitive neuroectodermal tumors (pPNET)
arise in soft tissues and bone. In humans, intraosseous primitive neuroectodermal tumor
is called Ewing sarcoma in this location, but this type of tumor may sometimes exhibit
epithelial differentiation. Nephroblastomas which originate from nephrogenic rests of the
metanephric blastema have also been reported in extrarenal sites, including the retroperitoneum,
spinal cord, and spinal canal and pelvic canal so check the kidneys for possible
unilateral or bilateral nephroblastoma rarely noted in adult dogs. There is no mesenchymal
differentiation which is typical of most nephroblastomas. There is no squamous or
odontogenic differentiation either. Nephroblastoma is typically noted in juvenile dogs and
sometimes in adult dogs. Such neoplasms are locally invasive and may sometimes metastasize
primarily to the liver, mesentery, and lungs; however, the contralateral kidney, adrenal
gland, thyroid, urinary bladder, and bone can be affected. P
Figure 3
Figure 1
Figure 2
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MARCH 2022
PULSE

Pulse - March 2022

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