Page 302 - Canine Lameness

274 17 Neoplastic Conditions of the Thoracic Limb

malignant due to osteosarcoma. Other tumor types include chondrosarcoma, fibrosarcoma, soft
tissue sarcoma, hemangiosarcoma, and histiocytic sarcoma. In fact, the shoulder is one of the three
most common joints to develop periarticular histiocytic sarcoma. Villonodular synovitis of the
shoulder has also been described in four dogs. Although an infrequent cause of lameness, lipomas
in the axillary area can become large enough to interfere with normal range of motion.
Palpation of this region must include the proximal humerus and scapula, which can reveal a
mass effect or pain in the presence of a tumor. The axillary region needs to be carefully palpated,
by sliding a hand in between the body wall and scapula from caudal to the scapula. Deep palpation
of the area may reveal a mass effect or pain, which is suggestive of tumors of the brachial plexus
(Section 17.2.5).
Compared to lesions of the distal radius, subtle lesions of the bones of the shoulder region can
be more easily missed on radiographs (Figure 17.2). This is due to the larger muscles surrounding
the area and greater difficulty positioning the dog to take radiographs, which often leads to super-
imposition of the shoulder region over the chest. As such, sedation to allow for appropriate posi-
tioning or advanced imaging such as CT should be considered if osseous neoplasia is a differential
diagnosis. Similarly, if a mass (suspected primary bone tumor) cannot be confidently palpated,
FNAs of the bone may require ultrasound guidance to direct the needle through the large muscle
coverage into the bone. Minimally invasive biopsy procedures of the bone performed with a
Jamshidi needle are best performed with image guidance via fluoroscopy, radiographs, or CT.
Given the proximal location, osseous neoplasia of the region is most frequently treated with
either radiation therapy or full limb amputation. Scapulectomy is a treatment option for scapular
tumors (Montinaro et al. 2013).

17.2.5 Nervous System
Tumors affecting the nervous system can be divided into those affecting the intracranial nervous
tissues, the spinal cord, or peripheral nerves. The latter two may cause unilateral symptoms and
are therefore important differential diagnoses for patients with lameness.

17.2.5.1 Spinal Cord Tumors
Spinal tumors are uncommon in dogs (McEntee and Dewey 2013). The clinical signs can be insidious,
chronic, and progressive (e.g. slow growing tumors), but can also be acute (e.g. acute hemorrhage of a
chronic tumor). The neurologic signs vary according to the location of the tumor and their severity
depends on the degree of compression, neural tissue destruction, edema, and hemorrhage, as well as
the degree of compensation of the spinal cord. Similarly, neurologic signs attributed to the presence of
spinal neoplasia can be unilateral, bilateral symmetrical, or asymmetrical. Spinal hyperesthesia is
common in instances where the tumor is found in the extradural or intradural‐extramedullary loca-
tion (see below) and may be the only abnormal finding. Animals with intramedullary tumors may not
have spinal hyperesthesia as there are no nociceptors within the spinal parenchyma. If the mass
expands to the point of stretching the meninges, or nerve roots, focal spinal hyperesthesia may result.
Advanced imaging (most frequently MRI) is generally required to detect tumors affecting the
function of the spinal cord. The only exception is tumors that cause significant lytic or proliferative
changes to the vertebrae, which can be seen on radiographs. FNAs and biopsies can be challenging
to acquire depending on the location of the lesion with respect to the nervous tissue. Cerebrospinal
fluid (CSF) analysis is typically abnormal (e.g. increased protein concentration, with or without
elevated cell count) but usually does not provide specific information about the tumor type since
neoplastic cells are rarely found unless the tumor is intradural or involves the meninges. Lymphoma