Page 176 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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Mesenchymal Tumours and Other Neoplasms
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Table 9.1. Histiocytic diseases of dogs affecting the skin and subcutis.
VetBooks.ir Cell of origin Key clinical features Key cytological features Immunophenotype

Langerhans cells
• Solitary, dome-shaped,
Histiocytoma
• Small lymphocytes
CD18, E-cadherin,
exophytic, often red, • Histiocytes CD1a, CD11c/
cutaneous masses, (during the IBA1
often alopecic and/or regression phase)
ulcerated
• Benign clinical
behaviour, regression
often observed
Cutaneous Langerhans cells • Multiple cutaneous • Histiocytes CD1a, CD11c/
Langerhans nodules, which may • Morphology similar CD18, E-cadherin,
cell histiocyto- either regress or to histiocytoma. IBA1
sis (LCH) become coalescent Anisokaryosis
and ulcerate and anisocytosis
• Largely benign can be more
process, involvement pronounced and
of lymph nodes and multinucleation
internal organs is may be observed
uncommon and is
associated with poorer
prognosis
Cutaneous Interstitial • Multiple cutaneous • Mixed cell CD1a, CD4, CD11c/
(reactive) dendritic cells and subcutaneous population CD18, CD90, IBA1
histiocytosis nodules, often • Prevalence of
(CH) ulcerated. When histiocytes and
disseminated, it is small lymphocytes
referred to as systemic • Other
histiocytosis (SH) inflammatory
• Spontaneous cells may be
regression is common present
Histiocytic Interstitial • Solitary or multiple • Pleomorphic CD1a, CD11c/
sarcoma (HS) dendritic cells subcutaneous masses. population of CD18, IBA1
When involving distant discrete to slightly
sites it is referred to as spindloid cells with
disseminated variable features of
histiocytic sarcoma atypia
• Prognosis is poor
especially in the
disseminated form