Page 127 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

106 PART I The Biology and Pathogenesis of Cancer

Renal Manifestations of Cancer Peripheral Neuropathy

VetBooks.ir Glomerular Disorders Paraneoplastic peripheral nerve lesions are relatively common.
When peroneal and ulnar nerve fibers were analyzed from dogs
A variety of paraneoplastic glomerular disorders have been
with a wide variety of cancers, paranodal/segmental demyelin-
reported in people. Membranous nephropathy is reported most ation and remyelination were seen most commonly, followed by
commonly and is associated with a variety of solid tumors. 1,188 axonal degeneration manifested by myelin ovoids and myelin
It is hypothesized that tumor antigens are deposited in the glom- globules. 205,206 These lesions are also reported in normal dogs with
eruli, and antibodies then bind to form immune complexes that increasing age, but 16 of 21 dogs had a significantly greater num-
1
activate complement. Paraneoplastic glomerular disorders likely ber of lesions compared with age-matched controls. 205 Tumors
are underreported in veterinary cancer patients with only two case associated with the highest percentages of abnormalities were
reports, one in a dog with primary erythrocytosis and one in a dog bronchogenic carcinoma, mammary adenocarcinoma, melanoma,
with lymphocytic leukemia. 189,190 insulinoma, and osteosarcoma. Interestingly, though, none of the
dogs in that study showed clinical signs consistent with a diffuse
Miscellaneous Syndromes or localized neuropathy. Clinical paraneoplastic polyneuropathies,
usually characterized by diffuse lower motor neuron signs, are
Paraneoplastic nephrogenic diabetes insipidus was reported much less common. They have been reported in dogs with insuli-
in a dog with intestinal leiomyosarcoma. 191 In addition, PU noma, multiple myeloma, lymphoma, fibrosarcoma, leiomyosar-
and PD and renal damage are commonly reported in dogs with coma, anaplastic sarcoma, pancreatic adenocarcinoma, prostatic
paraneoplastic hypercalcemia, and occasionally in cats (see ear- adenocarcinoma, combined mixed mammary gland adenoma and
lier). PU and PD also were reported in the rare cases of ectopic pulmonary adenoma, and combined pulmonary carcinoma and
adrenocortoctropic hormone syndrome identified in dogs (see metastatic HSA, and in a cat with renal lymphoma. 207–213
earlier).
Miscellaneous Manifestations of Cancer
Neurologic Manifestations of Cancer
Hypertrophic Osteopathy
Myasthenia Gravis
Hypertrophic osteopathy (HO) is a generalized osteo productive
Paraneoplastic myasthenia gravis (MG) is reported most com- disorder of the periosteum that affects the long bones of the
monly in dogs and cats with thymoma, 192–200 but it also has been extremities, typically beginning on the digits and then progressing
reported in dogs with osteosarcoma, cholangiocellular carcinoma, proximally. Lesions typically are bilaterally symmetric and involve
oral sarcoma, and nonepitheliotropic cutaneous lymphoma. 201–204 all four limbs. 214 Paraneoplastic HO is most commonly associ-
As with all forms of acquired MG, this is an immune-mediated ated with primary lung tumors or tumors that have metastasized
disease where antibodies are formed against nicotinic acetylcho- to the lungs. Two studies both reported that the majority of dogs
line (ACh) receptors on the postsynaptic sarcolemmal surface with paraneoplastic HO presented with pulmonary metastasis,
within the neuromuscular junction. Interestingly, patients with and the most common tumor type was osteosarcoma. 214,215 Para-
thymomas have been diagnosed with a variety of other immune- neoplastic HO without evidence of pulmonary involvement has
mediated diseases as well: exfoliative dermatitis and pemphigus been reported in dogs with renal transitional cell carcinoma and
vulgaris in cats; 185,200 polyarthritis, masticatory muscle myositis, nephroblastoma, urinary bladder botryoid rhabdomyosarcoma,
perianal fistula, immune-mediated thrombocytopenia, and hypo- hepatocellular carcinoma, esophageal adenocarcinoma, prostatic
thyroidism in dogs. 192 carcinoma, and malignant schwannoma derived from the vagus
Generalized MG is associated with appendicular muscle weak- nerve, 132,216–221 and in cats with adrenocortical carcinoma and
ness that is often but not always exercise induced. Concurrent renal adenoma. 222,223 Nonneoplastic diseases associated with
weakness involving the muscles of the esophagus (megaesopha- HO include infectious/inflammatory lung disease, Dirofilaria
gus), face, pharynx, and/or larynx can be present as well. Focal immitis infection, bacterial endocarditis, patent ductus arteriosus
myasthenia gravis most commonly involves these latter muscle with right-to-left shunting, Spirocera lupi esophageal granulomas,
groups. The definitive diagnosis for acquired MG usually is made esophageal foreign body, and congenital megaesophagus. 214 Idio-
by demonstrating circulating antibodies against ACh receptors, pathic HO has been reported in cats. 224,225 Cats with primary
although a small percentage of patients are seronegative. A posi- lung tumors can also develop digital metastasis, which can have a
tive edrophonium chloride challenge test is also helpful in dogs similar clinical presentation to HO. 226
with generalized MG. Affected patients most commonly present with swelling and/
Surgical removal of the thymoma and/or RT is recommended to or edema of the distal limbs and lameness or difficulty ambulat-
help reduce anti-ACh receptor antibody levels and improve clinical ing. Limbs are often painful on palpation and/or warm to the
signs of MG, but response is inconsistent. 195–198 In recent studies, touch. 214,215 One study also reported a high incidence of con-
neither MG nor megaesophagus affected prognosis in dogs or cats current bilateral serous to mucopurulent ocular discharge and
with thymoma. 192,198,199 However, patients with megaesophagus episcleral injection. 214 Fewer than half of affected patients have
have a high risk of aspiration pneumonia, and this is a common respiratory signs at the time of initial presentation. 214 When
cause of perioperative morbidity and mortality. 192,193,198 Therefore, radiographs are taken of the distal extremities, symmetric peri-
whenever possible, it is recommended that clinical signs of MG osteal new bone formation appears nodular or speculated, classi-
be controlled before anesthesia and surgery. Consultation with a cally radiating 90 degrees from the long axis of the affected bones
neurologist regarding anticholinesterase therapy (pyridostigmine (Fig. 5.3). There also is often evidence of adjacent soft tissue
bromide) and immunosuppressive therapy is recommended. swelling and edema.