JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1963156): Parakeet
HISTORY: Cutaneous mass from the wing.
HISTOPATHOLOGIC DESCRIPTION: Feathered skin (2 sections): Diffusely expanding the dermis and subcutis and widely separating feather follicles are multiple, coalescing lipid granulomas (xanthogranulomas). Granulomas are centered on aggregates of lipid, scant eosinophilic cellular debris and numerous linear, up to 300um, clear acicular clefts (cholesterol clefts). Cholesterol clefts are surrounded by numerous tightly packed epithelioid macrophages with abundant eosinophilic cytoplasm that contains many small, clear, discrete vacuoles (lipid). These are further surrounded by multinucleate giant cells with up to 40 nuclei that are arranged centrally (foreign body type), peripherally (Langhans type), or have a central area of dense eosinophilic cytoplasm bordered by multiple nuclei arranged in a circle that are surrounded by a peripheral rim of clear cytoplasm (Touton type). Multifocally there are low numbers of lymphocytes, heterophils and fewer plasma cells. There is mild epidermal hyperplasia with minimal orthokeratotic hyperkeratosis and mild intercellular edema.
MORPHOLOGIC DIAGNOSIS: Feathered skin: Lipid granulomas (xanthogranulomas), multiple, coalescing, with Touton type multinucleate giant cells, and acicular cholesterol clefts, parakeet, avian.
ETIOLOGIC DIAGNOSIS: Cutaneous xanthoma
SYNONYM: Xanthomatosis, xanthogranulomas
- Xanthoma means "yellow mass"
- Tumor-like swellings characterized by accumulations of lipid-laden macrophages, multinucleate giant cells, free cholesterol, and variable amounts of connective tissue
- Occurs in gallinaceous and psittacine birds, Siamese cats and rarely dogs
- Significant chicken flock problem in the 1960s, primarily affecting white leghorns
- An accumulation of excess lipids in the body due to disturbances of lipid metabolism and marked by formation of fatty masses
- Idiopathic in birds and Siamese cats; likely some type of disturbance in lipid metabolism
- Pathogenetic theories include high-lipid diets, fat-soluble toxins
- Trauma may predispose to formation
- Idiopathic lesions in chickens have been linked to diets with high levels of chlorinated hydrocarbons
- Abnormal plasma concentrations of cholesterol, triglycerides, or lipoproteins (dyslipoproteinemias)
- Dyslipoproteinemias can be inherited or acquired
- Acquired dyslipoproteinemias include diabetes mellitus and hyperadrenocorticism; lesions abate with resolution of primary disease
TYPICAL CLINICAL FINDINGS:
- Birds are bright and active with normal egg production and feed consumption
- Yellow, single to multiple, discrete subcutaneous nodules or diffuse skin thickening
- The skin may be featherless, ulcerated, or hemorrhagic
- No age, breed or sex predilection, except more frequently seen in female budgerigars
- Hypercholesterolemia and hyperlipidemia, occasionally
TYPICAL GROSS FINDINGS:
- Initially lesions are soft, fluctuant and contain a yellow transudate.
- Become firm with chalky white areas of cholesterol
- Nodules are interfollicular and occur anywhere on the skin; may overlie other neoplasms especially lipomas
- Found on the breast, abdomen, feathered portion of the leg or wattles, eyelid and third eyelid
- Infrequently are periarticular or involve the oral cavity
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Nodular to diffuse infiltration of foamy macrophages, acicular cholesterol clefts, and multinucleate giant cells (Touton type)
- Lipid lakes are prominent throughout the affected dermis
- Granulomatous inflammation and fibroplasia may occur
ADDITIONAL DIAGNOSTIC TESTS:
- Oil-red-O stained frozen sections have positive staining of lipid within macrophages, giant cells and in extracellular lakes
- Polarized frozen sections have birefringent rhombic crystals with typical "Maltese cross" of cholesterol esters
For gross findings:
- Infectious and noninfectious granulomas – differentiate on histology
- Gout - differentiate on histology; gouty tophi
- Atypical mycobacterial infection
- Neoplasms - especially histiocytic or fibrohistiocytic; Marek’s disease associated cutaneous lymphoma (usually affect feather follicles)
- Secondary to acquired or inherited dyslipoproteinemias in other animals
- Reported as secondary lesion in dogs and cats with diabetes mellitus, hypothyroidism, and hyperadrenocorticism
- Xanthomas occur on the thorax of horses with hyperadrenocorticism
- Watanabe heritable hyperlipidemic rabbits (WHHL) develop xanthomatosis secondary to hypercholesterolemia due to a single genetic defect for low-density-lipoprotein (LDL) receptors leading to decreased cell uptake and increased production of LDL
- High incidence in female geckos, per one report
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- Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. New York, NY: Elsevier; 2016:700.
- Goldschmidt MH, Hendrick MJ. Tumors of the skin and soft tissue. In: Meuten DJ ed. Tumors in Domestic Animals. 4th ed. Ames, IA: Iowa State Press; 2002: 111-112.
- Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Diseases of the dermis. In: Skin Diseases of the Dog and Cat. 2nd ed. Ames, IA: Blackwell Publishing; 2005: 330-333.
- Jones TC, Hunt RD, King NW. In: Veterinary Pathology. 6th ed. Baltimore, MD: Williams and Wilkins; 1997: 869-870.
- Schmidt RE, Reavill DR, Phalen DN. Pathology of Pet and Avian Birds. Ames, IA: Blackwell Publishing; 2003:145,194,198-9.
- Miller WH, Griffin CE, Campbell CL. Muller and Kirk’s Small Animal Dermatology. 7th ed. St. Louis, MO: Elsevier; 2013:542.
- Shivaprasad HL. Miscellaneous diseases. In: Boulianne M, ed. Avian Disease Manual. 7th Jacksonville, FL: American Association of Avian Pathologists; 2013; 224, 260, 291.