Page 966 - Cote clinical veterinary advisor dogs and cats 4th

474 Histiocytic Diseases

GENETICS, BREED PREDISPOSITION PHYSICAL EXAM FINDINGS Initial Database
• Bernese mountain dogs (BMDs) are predis- • Histiocytomas occur most often as raised, • CBC, serum chemistry profile, and urinalysis;
VetBooks.ir BMDs, heritability is oligogenic and almost monly found on the extremities and head histiocytic diseases, except hemophagocytic
no characteristic or specific findings with
hairless, erythematous masses and are com-
posed to many types of histiocytic disease. In
(especially the pinnae).
certainly not autosomal or sex-linked.
syndrome results in Coombs-negative anemia
• Other breeds overrepresented in histiocytic
diseases include golden retrievers, flat-coated • Focal lesions typically involve a pal- and thrombocytopenia. Hypoalbuminemia
may be present.
pable mass, often on the extremities. If
retrievers (FCRs [44% of all tumors]), the mass is subarticular, lameness may • Fine-needle aspiration of accessible masses
rottweilers (especially periarticular HS), and be prominent, especially with bone and lymph nodes for cytologic exam (look
Doberman pinschers. involvement. for multinucleated giant cells and erythro-
• Abnormalities in tumor suppressor genes • Splenomegaly may be present with dis- phagocytosis by macrophages)
(e.g., RB1 [retinoblastoma], PTEN) have seminated HS, is common with hemophago- • Biopsy of affected tissue with immunohis-
been implicated in HS in BMDs and FCRs. cytic HS, and can correlate with a worse tochemistry (see Pearls & Considerations
• Shar-peis were overrepresented in LCH cases. prognosis. below)
• Retrievers and Pembroke Welsh corgis may • Dogs with disseminated HS often have • Radiography of affected area if bony
be overrepresented in central nervous system significant pulmonary involvement and may involvement is suspected typically reveals
(CNS) HS. be dyspneic with advanced disease. Cough a lesion that is permeative, punctate, or
• Irish wolfhounds may have a genetic pre- is a common presenting complaint. moth-eaten.
disposition for SH. • With systemic histiocytosis, skin lesions may • Thoracic radiography to evaluate pulmonary
• No breed predisposition has been reported be seen on the nasal planum, muzzle, flank, parenchyma for nodules (often large) and
in cats. scrotum, as well as the periocular tissues. lymphadenopathy (especially sternal or
Skin lesions in CH and SH are typically tracheobronchial)
RISK FACTORS nodular to plaque-like. • Abdominal ultrasound to screen for visceral
In a study of affected and unaffected BMDs, • Generalized lymphadenopathy may be involvement
dogs with orthopedic disease were at greater appreciated with systemic histiocytosis and • Bone marrow aspiration and cytology
risk for developing HS (OR = 2.5), and dogs disseminated HS. may be indicated if systemic disease is
treated with prescription anti-inflammatory suspected and more than one cell line
medications had a lower risk (OR = 0.42). Etiology and Pathophysiology is abnormal (especially low) on CBC
• Largely unknown in dogs, although oligo- (p. 1068).
GEOGRAPHY AND SEASONALITY genic inheritance has been shown in BMDs,
Initially, histiocytosis in BMD primarily affected and 25% of BMDs are affected by clinical Advanced or Confirmatory Testing
dogs from Switzerland, where the breed origi- histiocytic sarcoma. Association with prior • CT scan of affected area if focal and consider-
nated. Many cases have now been reported in joint disease (e.g., arthritis) has been shown ing resection
dogs born in the United States and the United in this breed. • Immunohistochemistry on biopsy tissue (see
Kingdom (especially FCRs). • Hemophagocytic histiocytic sarcoma is of Pearls & Considerations below)
macrophage origin and originates in the
Clinical Presentation splenic red pulp or bone marrow.
DISEASE FORMS/SUBTYPES TREATMENT
• As detailed above, histiocytic diseases are DIAGNOSIS Treatment Overview
either local or diffuse, and are reactive, For benign/reactive disease, immunosuppres-
benign, or malignant. They can occur Diagnostic Overview sion may suppress disease, but lesions are often
anywhere in the body, including the CNS Histiocytic diseases in dogs and cats can resistant to treatment. These lesions can wax
or lungs as a primary site. be distinguished from each other based on and wane, making it difficult to assess response
• A hemophagocytic variant that occurs in dogs clinicopathologic findings, including site(s) to treatment. For malignant disease, if only
and cats leads to anemia and thrombocyto- of involvement. Diagnosis is based on cytol- local involvement is present, surgical removal
penia. This variant is very aggressive. ogy and histopathology, and the latter often should be followed by adjuvant CCNU-
requires immunohistochemistry to define based chemotherapy. For disseminated disease,
HISTORY, CHIEF COMPLAINT ontogeny. After biopsy confirmation, staging CCNU-based chemotherapy and palliative
• Most dogs are presented for signs refer- should include general assessment to establish care may extend survival time, but long-term
able to the primary tumor (presence of a the health of the animal and a thorough prognosis is poor. Dogs with anemia, thrombo-
mass). evaluation of regional lymph nodes with cytopenia, and hypoalbuminemia often survive
• Dogs with CH and SH are typically presented cytology. Abdominal ultrasound is advised less than 1 month, even with CCNU therapy.
for evaluation of skin lesions. because visceral involvement is common with Histiocytomas often spontaneously regress
+
• SH can have ocular involvement, and patients some forms. Thoracic radiographs are very through actions of CD8 T lymphocytes but
may be presented for evaluation of ocular important because pulmonary metastasis often can be bothersome enough to warrant surgical
signs. occurs. excision with an excellent prognosis.
• Dogs with periarticular HS are usually
presented for evaluation of a soft-tissue mass Differential Diagnosis Acute General Treatment
or lameness. • Granulomatous disease • Patients with malignant histiocytosis and
• Disseminated HS is a much more insidious • Lymphoma significant erythrophagocytosis may require
disease because masses are primarily visceral • Poorly differentiated mast cell tumor red blood cell transfusion (p. 1169), ideally
(spleen, liver, bone marrow, lymph nodes, • Anaplastic sarcoma or carcinoma in conjunction with initiation of therapy to
lungs). Cutaneous and subcutaneous masses • Synovial sarcoma (joint tumors) abort red cell loss.
are uncommon. • Other soft-tissue or bone sarcomas (for local • Dyspneic patients with malignant histiocy-
• Affected dogs and cats are often presented disease) tosis may benefit temporarily from oxygen
for evaluation of nonspecific systemic • Immune-mediated hemolytic anemia and therapy, but the prognosis is grave when the
signs such as lethargy and anorexia/weight immune thrombocytopenia (hemophagocytic disease has reached the point of producing
loss. form) respiratory compromise.

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