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Canine Sterile Papular and Nodular Skin Diseases
Sandra Diaz, DVM, MS, DACVD

Department of Veterinary Clinical Sciences, Ohio State University, Columbus, OH, USA

This chapter will review the etiology, pathogenesis, antigen‐presenting cells, admixed with T lymphocytes
diagnosis, management, and prognosis of the most and neutrophils. The cellular phenotype has become the
common canine sterile papular and nodular derma- basis for definitive diagnosis (see diagnosis section below).
toses, including histiocytic disorders, sterile nodular
panniculitis, sterile granuloma/pyogranuloma syndrome, Epidemiology
and juvenile cellulitis. Age at the time of diagnosis ranges from 3 to 9 years and
males and females can both be affected, but one study
showed male predilection. Collies and Shetland sheep-
Canine Histiocytic Disorders dogs may be predisposed.

Canine histiocytic disorders include canine reactive his- Clinical Signs
tiocytosis (cutaneous and systemic) and histiocytic sar- Cutaneous histiocytosis is characterized by multiple
coma complex (localized and disseminated histiocytic hairless, erythematous dermal to subcutaneous nodules
sarcoma). localized predominantly to the face, neck, nasal mucosa,
perineum, scrotum, and feet (Figures 164.1 and 164.2).
The lesions are not pruritic or painful, but larger lesions
Canine Reactive Histiocytosis may become ulcerated and cause discomfort. The lesions
Canine reactive histiocytosis includes systemic histio- wax and wane, with older lesions spontaneously regress-
cytosis (SH) and cutaneous histiocytosis (CH). Both ing as new ones form. The disease is usually slowly pro-
forms are characterized by reactive proliferation of acti- gressive and, in some cases, may spontaneously resolve.
vated dermal dendritic cells. They affect mainly the
skin and subcutaneous tissue, but in the systemic form Diagnosis
other organ systems can be involved, including lymph The clinical differential diagnoses include other nodular
nodes, eyelids, sclera, nasal cavity, lungs, spleen, and skin diseases such as neoplasia (e.g., multiple cutaneous
bone marrow. histiocytomas, mast cell tumors, cutaneous lymphoma),
infectious granulomas, sterile nodular panniculitis,
Cutaneous Histiocytosis and cutaneous sterile granuloma and pyogranuloma
Etiology/Pathophysiology syndrome.
The etiology and pathogenesis of CH are unknown. Since Diagnosis is based on the patient’s history, clinical
infectious agents have not been identified and the disease signs, cytologic findings, and primarily histopathologic
responds to immunosuppressive therapy, immune‐ findings. Immunohistochemistry may be required to
dysregulatory mechanisms are likely involved. This dis- confirm the diagnosis.
ease is characterized by specific morphologic and Cytologic examination shows large numbers of histio-
immunohistochemistry criteria. According to Affolter cytes with abundant cytoplasm; binucleated and multi-
and Moore, CH originates from CD1+, CD11c+, MHC nucleated cells can be seen. Variable numbers of other
II+, CD4+, and Thy‐1+ (CD90) activated dermal dendritic inflammatory cells can be present.

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical