Page 688 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

666 PART IV Specific Malignancies in the Small Animal Patient

Tumors of the Spinal Cord spinal cord tumor diagnosed in dogs and cats. 125,126,131 Approxi-
mately 15% of spinal cord neoplasms are intramedullary (IM),
VetBooks.ir Classification and Epidemiology although up to one-third of tumors may involve multiple com-
partments.
125–127,134,135
In dogs, ependymomas and gliomas are
As with brain tumors, SC neoplasms are classified as primary or
the most frequently diagnosed primary IM tumors, and HSA and
secondary according to their tissue of origin. However, a classifica- transitional cell carcinoma are the most common secondary IM
tion scheme based on the tumor location relative to the neuraxis tumors. 135
(Table 31.2) is the most commonly used method of clinical clas- In dogs and cats, CNS lymphoma may affect any or all com-
sification of tumors affecting the SC in veterinary medicine. The partments of the SC and may occur as a primary or secondary
overall incidence in dogs and cats is unknown, but SC tumors tumor. 77,136–139 Lymphoma is the second most prevalent SC dis-
appear to be less common than intracranial neoplasms. ease of cats and the most common feline SC tumor, although 85%
Extradural tumors account for approximately 50% of all of cases of SC lymphoma in cats are secondary and part of a mul-
tumors affecting the SC and frequently arise from the vertebrae. ticentric process. 137–139 Older studies report that 80% to 90% of
Vertebral tumors such as osteosarcoma (OSA), chondrosarcoma cats with CNS lymphoma were seropositive for FeLV p27 antigen;
(CSA), plasma cell tumors, fibrosarcoma (FSA), and HSA are a more recent reported indicated that only 56% of cats with CNS
commonly encountered extradural tumors (Fig. 31.5; see Table lymphoma were infected with FeLV. 138,140 This may reflect the
31.2) 125–133 Intradural-extramedullary (ID-EM) tumors account decreasing overall prevalence of feline retroviral infections attrib-
for 35% of all tumors, and meningiomas are the most common utable to vaccination and improved management practices, or
ID-EM tumor (Fig. 31.6) and also the most common primary infer the importance of other factors that contribute to develop-
ment of CNS lymphomas. 141 Cats with lymphoma are typically
younger (median 4 years) at diagnosis than cats with other tumor
types affecting the SC (median 9 years). 138
TABLE 31.2 Clinical Classification and Examples of Large-breed, older dogs are predisposed to the development
Tumors Affecting the Spinal Cord of vertebral tumors. 129,130 SC tumors such as ependymomas and
Anatomic Location Relative to Spinal Cord nephroblastomas are more commonly seen in dogs less than 6 years
old. 142,143 Young German shepherd dogs and golden retrievers
Extradural Intradural-Extramedullary Intramedullary
(<3 years of age) are predisposed to nephroblastoma. 142,143 Boxer
Osteosarcoma Meningioma Astrocytoma dogs were overrepresented in one study of intraspinal meningio-
mas, and both boxers and other brachycephalic breeds are predis-
Chondrosarcoma Peripheral nerve sheath Ependymoma posed to tumors of glial origin. 131,134
tumor
Fibrosarcoma Nephroblastoma Oligodendroglioma
Pathophysiology, History, and Clinical Signs
Plasmacytoma Histiocytic sarcoma Gliomatosis cerebri
Dogs and cats with SC tumors commonly present for progres-
Multiple myeloma Lymphoma Hemangiosarcoma sive myelopathic signs reflecting the neuroanatomic location of
Lymphoma Transitional cell the tumor with or without evidence of pain. Tumors in ED or
carcinoma ID-EM locations cause clinical signs of neurologic dysfunction,
mainly by compression of the spinal cord or nerve roots by the
Hemangiosarcoma Lymphmoma
neoplasm (see Fig. 31.6). IM tumors may cause signs of spinal
Various carcinomas cord disease by compression, invasion, or destruction of the SC
parenchyma, as well as by obstructing CSF flow and inducing

A B G

C D E F H
• Fig. 31.5 Imaging features of extradural vertebral tumors. Lytic and sclerotic lesion in the C2 spinous
process (A, arrow) and corresponding postcontrast MRI (B) illustrating spinal cord compression from a
plasmacytoma. Radiographic lysis in the L4 lamina and pedicle (C), and corresponding sagittal MRI (D)
demonstrating chondrosarcoma. Normal lumbar spinal radiograph (E) in dog with multifocal hyperintense
foci of lymphoma in the vertebral bodies on MRI (F). MRI (G) and CT-guided needle biopsy (H) of T3 osteo-
sarcoma.