Page 1506 - Clinical Small Animal Internal Medicine

1444 Section 12 Skin and Ear Diseases

to the lungs, lymph nodes, and abdominal viscera has and prednisone has also been reported to induce a tem-
VetBooks.ir been reported in up to 91% of cases. Affected dogs are porary response.
usually presented for lameness or a soft tissue swelling.
In dogs with disseminated HS, the clinical signs are
In general, the prognosis is poor. Dogs with localized
vague and include anorexia, lethargy, and weight loss. Prognosis
Pulmonary involvement is common and dogs may show HS receiving aggressive localized treatment and sys-
evidence of dyspnea at the time of initial presentation. temic chemotherapy may have a better prognosis with
Neurologic abnormalities, including ataxia and parapa- a median survival time of 568 days. The median sur-
resis, are also common. Other organs often affected vival time for dogs with disseminated HS receiving
include the liver and spleen. Although clinicopathologic chemotherapy is 106 days. The presence of distant
findings are nonspecific, anemia, thrombocytopenia, metastasis or disseminated disease worsens the prog-
and hypoalbuminemia were consistently reported in nosis. Many dogs are euthanized at the time of diag-
cases of hemophagocytic HS. Diffuse splenomegaly nosis because of poor clinical condition and poor
with ill‐defined masses was also consistently present in prognosis.
these cases.

Diagnosis Sterile Nodular Panniculitis
The diagnosis is based on clinical signs, signalment, and
cytologic and histopathologic findings. The main clini- Panniculitis refers to inflammation of the subcutane-
cal differential diagnoses are other neoplasias and sys- ous fat and it may be associated with a variety of con-
temic histiocytosis. Both localized and disseminated HS ditions. Sterile nodular panniculitis (SNP) refers to
have the potential for highly aggressive behavior so sterile inflammation of the subcutaneous fat tissue of
complete staging to determine disease extent is recom- unknown origin. Clinical signs include single or mul-
mended to determine possible treatments and progno- tiple subcutaneous nodules, intermittent fever, and
sis. Cytologic finding include large round cells with anorexia.
foamy cytoplasm and multinucleated giant cells admixed Concurrent inflammation of the fat in other organs
with spindle‐shaped cells. Histopathologically, the tumors can be seen in cases of SNP. Skin lesions can be solitary
are poorly demarcated and the neoplastic infiltrate con- or multiple and multiple lesions can be associated with
sists of pleomorphic mononuclear cells and multinucleated systemic signs including fever, lethargy, and anorexia.
giant cells. Phagocytosis of neutrophils and erythro-
cytes is not uncommon. Marked anisokaryosis and
anisocytosis with high mitotic rate are also present. The Pathogenesis
histopathologic findings and the use of immunohisto-
chemical staining help differentiate these tumors from Sterile nodular panniculitis has been documented in
other round cell tumors. association with systemic lupus erythematosus, pancrea-
Recently, a screening program has been proposed for titis and pancreatic tumors, rheumatoid arthritis, and
early detection of disseminated HS in Bernese mountain lymphoplasmacytic colitis. In people, a deficiency of
dogs. The program suggests screening of Bernese moun- alpha‐1‐antitrypsin, a protease inhibitor, has been sug-
tain dogs over 4 years of age every six months, including gested to be a predisposing factor. In dogs, this associa-
diagnostic imaging and measurement of ferritin as a tion has not been made with certainty. In one dog with
blood‐borne marker of the disease. panniculitis in which alpha‐1‐antitrypsin was found to
be low, a Bartonella infection was present, making it dif-
Therapy ficult to determine the cause. In one retrospective study,
For cases of localized HS, improved outcome has been 37% (16/43) of the patients had prior surgery with lesions
reported with the use of localized therapy, including sur- developing at the surgery site.
gery and radiation therapy. Unfortunately, the rate of
metastasis is very high (up to 91%) so the use of adjuvant Signalment
systemic therapy may be beneficial. The disseminated
form of the disease usually has poor sensitivity to chem- A large retrospective study did not identify any age,
otherapy. Lomustine, doxorubicin, and vincristine have breed or sex predilection; however, others suggest 3–5
been used with variable success. The use of bisphospho- years as the most common age of onset and dachshunds,
nates has been proposed to increase the effectiveness of miniature poodles, and collies as the breeds at increased
chemotherapy against HS cells. The use of a multiple risk for SNP. In two studies, the most affected dogs were
drug protocol including cyclophosphamide, vincristine, neutered, suggesting no gender predilection.