Page 174 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Mesenchymal Tumours and Other Neoplasms
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Other canine histiocytic disorders
VetBooks.ir Cutaneous Langerhans cell histiocytosis (LCH) and (reactive) cutaneous histiocytosis (CH).

Clinical features
• Canine cutaneous Langerhans cell histiocytosis (LCH):
• Largely benign tumour of histiocytic origin, deriving from Langherans cells
(LCs).
• Multiple lesions (up to several hundred) ranging from nodules to masses, which
may undergo spontaneous regression or may extend and ulcerate in approxi-
mately 50% of the cases.
• Involvement of lymph nodes and internal organs may occur. This is associated
with poor prognosis.
• Over-represented canine breed: Shar Pei.
• Canine cutaneous (reactive) histiocytosis (CH):
• Histiocytic inflammatory disease deriving from the interstitial dendritic cells and
causing, together with T-lymphocytes, a lympho-histiocytic vasculitis. When in-
volving lymph nodes and other organs, it is defined as systemic histiocytosis (SH).
• Multiple cutaneous and subcutaneous nodules, often ulcerated. Head, face,
trunk, scrotum, nose and extremities are considered preferred locations. New
lesions may appear at different sites.
• Spontaneous regression is common.

Cytological features
• Canine cutaneous Langerhans cell histiocytosis:
• Histiocytic cells are similar to those observed in histiocytoma.
• Anisokaryosis may be more prominent than in histiocytoma and multinucleation can be
present, especially in clinically aggressive cases. However, this is not a consistent feature.
• Canine cutaneous (reactive) histiocytosis:
• Aspirates yield a mixed cell population with prevalence of histiocytes and small
lymphocytes. Histiocytes lack cytological atypia.
• Variable percentages of neutrophils, plasma cells and eosinophils may also be observed.

Differential diagnoses
• Canine cutaneous Langerhans cell histiocytosis (LCH):
• Cutaneous histiocytoma (when multiple lesions are present)
• Canine cutaneous (reactive) histiocytosis:
• Mixed (chronic) inflammation
• Inflamed cutaneous lymphoma