JPC SYSTEMIC PATHOLOGY
INTEGUMENTARY SYSTEM
August 2022
I-F08 (NP)

Signalment (JPC# 1665005):  Monkey

HISTORY:  None

HISTOPATHOLOGIC DESCRIPTION:  Slide A: Mucous membrane (site not specified):  Markedly expanding the submucosa are multifocal to coalescing nodular infiltrates predominately composed of macrophages admixed with moderate numbers of viable and necrotic neutrophils and fewer eosinophils, lymphocytes, plasma cells, and multinucleated giant cells (Langhans and foreign-body type) with variable amounts of eosinophilic cellular and karyorrhectic debris (necrosis), fibrin, hemorrhage, and edema. Occasionally these aggregates have central areas of necrosis bordered by macrophages and few neutrophils, further surrounded by fibroblasts and variably mature collagen (granulomas). Scattered throughout the inflammation and within multinucleated giant cells are numerous 4-8µm diameter round yeast with 1µm, thin, eosinophilic walls and clear centers that are surrounded by clear space that is up to 10µm thick (capsule and retraction artifact). Scattered similar inflammatory cells extend multifocally into the adjacent skeletal muscle, disrupting and separating myofibers. Myofibers are affected by one or more of the following: shrunken (atrophy), swollen with vacuolated cytoplasm and loss of cross striations (degeneration), or shrunken and hypereosinophilic with a pyknotic nucleus (necrosis). The superficial submucosa is expanded by fibrin, edema, few plasma cells, lymphocytes, and rare neutrophils.

Slide B:  Mucicarmine stain:  The yeast capsule is 3-8um thick and bright red (carminophilic). Yeast are 4-8um in diameter, occasionally clustered, and frequently exhibit narrow-based budding.  Yeast capsules are surrounded by a 10-15um thick, clear space (shrinkage artifact) with short, radiating, carminophilic spines extending from the capsule.

MORPHOLOGIC DIAGNOSIS:  Mucous membrane (site not specified):  Mucositis, pyogranulomatous, multifocal to coalescing, marked, with numerous yeast with thick carminophilic capsules, etiology consistent with Cryptococcus spp., monkey (species not specified), non-human primate.

ETIOLOGIC DIAGNOSIS:  Mucosal cryptococcosis

CAUSE:  Cryptococcus neoformans

SYNONYM:  European blastomycosis; torulosis

GENERAL DISCUSSION:

• Subacute or chronic mycotic infection in humans and a wide variety of animals with a predilection for the respiratory system (especially nasal region) and central nervous system; cutaneous and ocular lesions are seen less frequently
• Organism is dimorphic, saprophytic, fungus
• One of the few systemic mycoses that affects cats more commonly than dogs
• Pigeons are thought to be the most important vector; the pigeon’s high body temperature is thought to protect it from pathogenic infection
• Organism is not contagious and primarily infects animals that are immunocompromised, stressed, or treated for prolonged periods with corticosteroids
• Inflammation is mild compared to the number of organisms observed within lesions, but can be severe in cutaneous capsule-deficient strains

PATHOGENESIS:

• Opportunistic infection usually via inhalation
• Organisms are unencapsulated in the environment, increasing the chances of aerosolization; once in the respiratory system, they regain their capsule
• Can disseminate hematogenously or via lymphatics
• Can extend locally from the nasal cavity to the CNS
• Virulence factors
  • Polysaccharide capsule - prevents phagocytosis by macrophages, inhibits leukocyte migration, and inhibits recruitment of inflammatory cells
  • Melanin – antioxidant properties

TYPICAL CLINICAL FINDINGS:

• Majority of clinical signs are attributable to infection of the primary organ (i.e. lung, nasal cavity, skin, ocular, or CNS)

TYPICAL GROSS FINDINGS: (lesions in the skin)

• Well-circumscribed, firm small nodules which tend to ulcerate
• Draining tracts may be present which exude mucoid to serous exudate that contains organisms

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Yeast:
  • Foamy (“soap-bubble”) appearance due to unstained capsules of organisms
  • Pleomorphic, round or oval, thin‑walled cells (3.5-7um diameter) surrounded by a thick heteropolysaccharide capsule (1-30um diameter) that forms a clear or refractile halo
  • Reproduce by narrow-based budding
• Cutaneous lesions:
  • Inflammation is usually scant to absent in the skin
  • If present, inflammation consists of macrophages with engulfed organisms and variable numbers of neutrophils
  • Marked pyogranulomatous and eosinophilic dermatitis is associated with capsule-deficient neoformans

ULTRASTRUCTURAL FINDINGS:

• Capsule formed of filaments that anchor in the cell wall and radiate peripherally
• Microbody is found in cytoplasm – a modified peroxisome involved in metabolism of xanthine and urate; may underlie propensity to live in urate-rich bird feces

ADDITIONAL DIAGNOSTIC TESTS:

• Cytology of aspirate or direct smear: Negative staining of wide capsular zone by India ink
• Special/histochemical stains: Cell wall stains with mucicarmine, yeast bodies stain with PAS, GMS and Fontana-Masson; the clear halo that remains around the mucicarmine-stained organism is due to shrinkage of the capsule during fixation
• Culture: May take up to 6 weeks for positive culture
• Serologic tests: Latex agglutination procedure to identify capsular antigen

DIFFERENTIAL DIAGNOSIS:

• For microscopic findings, poorly encapsulated neoformans is difficult to differentiate from other unencapsulated fungi:
  • Blastomyces dermatitidis - lacks the wide capsule; has a distinct, double-contoured cell wall and exhibits broad-based budding
  • Histoplasma capsulatum var. capsulatum - smaller (2-5um); usually within macrophages
  • Coccidioides immitis - much larger (5-50um); reproduces by endosporulation rather than budding
  • Candida albicans - often forms yeast, hyphae, and pseudohyphae in tissue
  • Lacazia (Loboa) loboi – often forms chains of yeast in tissue
  • Sporothrix schenckii – smaller (3-8um); more pleomorphic, often cigar-shaped

COMPARATIVE PATHOLOGY:

• Most species acquire the respiratory or CNS form
• Cats:
  • Most common systemic fungal infection in the cat; Siamese cats may have an increased risk of infection
  • Upper nasal cavity is typically initial site of infection; also have CNS (extension through the cribriform plate), ocular, and cutaneous involvement; skin lesions occur in 40-50% of cases and are often on the face, pinnae, and paws
• Dogs:
  • Young, large breed dogs are overrepresented
  • Disseminated form more common
  • May occur in immunocompetent hosts
  • Skin lesions may occur on the nose, lips, tongue, and nail beds
  • One recent report of pyelonephritis
• Bovine: Associated with mastitis
• Goats: Rhinitis, meningitis, encephalitis and pneumonia. Rarely seen in sheep (Carmo PMSD et al, JDVI 2020)
• Llama: Report of infection in brain, spinal cord, lung, and kidney
• Elk: Report of meningoencephalitis and pneumonia
• Humans: Occurs in immunocompromised people, primarily CNS
• Cheetahs: Seen in both captive as well as free ranging cheetahs. The king cheetah subtype seems to have a predisposition suggesting there may be a genetic predisposing factor.  In all cheetahs certain behaviors (such as slapping the ground when threatened) is thought to predispose them more than other large cats.
• Koala: Due to the presence of Cryptococcus in a variety of eucalyptus species, this disease has been reported in both free ranging and captive koalas. Disease is usually localized to the nasal mucosa.  Environmental burden seems to be important. 
• Slender tailed cloud rats also seem to be a susceptible species.
• Cetacea: Occurs in Dolphins in porpoises. neoformans occurs worldwide while C. gattii is in tropical areas (especially associated with eucalyptus). Generally results in pneumonia and lymphadenitis.

REFERENCES:

1. Blauvelt M, Messick JB. The lymph nodes. In: Valenciano AC, Cowell RL, eds. Diagnostic Cytology and hematology of the dog and cat. 5th ed. St. Louis, MO: Elsevier; 2020: 176.
2. Boes KM. Body cavity fluids. In: Raskin RE, Meyer DJ, eds. Canine and Feline Cytopathology: A Color Atlas and Interpretation Guide. 4th ed. St. Louis, MO: Elsevier; 2023: 254.
3. Boes KM. Respiratory system. In: Raskin RE, Meyer DJ, eds. Canine and Feline Cytopathology: A Color Atlas and Interpretation Guide. 4th ed. St. Louis, MO: Elsevier; 2023: 189-191, 220-221.
4. Carmo PMSD, Uzal FA, Pedroso PMO, Riet-Correa F. Conidiobolomycosis, cryptococcosis, and aspergillosis in sheep and goats: a review. J Vet Diagn Invest. 2020 Nov;32(6):826-834.
5. Conrado FO. Fecal and rectal cytopathology. In: Raskin RE, Meyer DJ, eds. Canine and Feline Cytopathology: A Color Atlas and Interpretation Guide. 4th ed. St. Louis, MO: Elsevier; 2023: 394.
6. Craig LE, Dittmer KE, Thompson, KG. Bones and Joints.  In: Maxie MG Jubb, Kennedy,and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier; 2016:104.
7. Delaney MA. Treuting p.m.  Rothenberger JL.  In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 510-11.
8. Ewing PJ, Meinkoth JH, Cowell RL, Tyler RD. The kidneys. In: Valenciano AC, Cowell RL, eds. Diagnostic Cytology and hematology of the dog and cat. 5th ed. St. Louis, MO: Elsevier; 2020: 375.
9. Grimes CN, Fry MM, LeBlanc CJ, Hecht S. The lung and intrathoracic structures. In: Valenciano AC, Cowell RL, eds. Diagnostic Cytology and hematology of the dog and cat. 5th ed. St. Louis, MO: Elsevier; 2020: 277.
10. Gross TL, Ihrke PJ, Walder EJ, Affolter VK. In: Skin diseases of the dog and cat. 2nd ed. St Louis, MO: Blackwell publishing; 2005:291.
11. Higgins D. Rose K.  Spratt D.  Monotremes and Marsupials. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018:
12. Levine GJ, Cook JR. Cerebrospinal fluid and central nervous system cytology. In: Valenciano AC, Cowell RL, eds. Diagnostic Cytology and hematology of the dog and cat. 5th ed. St. Louis, MO: Elsevier; 2020: 216-217.
13. Miller, Jr. WH, Griffin CE, Campbell KL. In: Muller and Kirk’s Small Animal Dermatology. 7^th St. Louis, MO: Elsevier; 2013: 262-264.
14. Raskin RE, Conrado FO. Integumentary system. In: Raskin RE, Meyer DJ, eds. Canine and Feline Cytopathology: A Color Atlas and Interpretation Guide. 4th ed. St. Louis, MO: Elsevier; 2023: 52-53, 58.
15. Simmons J, Gibson S. Bacterial and mycotic diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T. Nonhuman Primates in Biomedical Research Volume 2: Diseases. 2nd ed. London, UK: Academic Press; 2012:156-157.
16. Leger J, Raverty S, Mena A. Cetacea. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 561.
17. Sykes JE, Malik R. In: Greene CE, ed. Infectious Diseases of the Dog and Cat. 4th ed. St. Louis, MO: Elsevier Saunders; 2012:621-634.
18. Terio KA. McAloose D. Mitchell E.  In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 278.
19. Young KM, Teixeira LBC. Eyes and associated structures. In: Valenciano AC, Cowell RL, eds. Diagnostic Cytology and hematology of the dog and cat. 5th ed. St. Louis, MO: Elsevier; 2020: 156.
20. Welle MM, Linder KE. The Integument. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:1178.

Click the slide to view.

---