2-year-old Domestic Short Hair – Intact

Species: FELINE
Breed: DSH
Age: 2y
Gender: MALE, INTACT

Source/History:                                                              

2-year-old intact male DSH cat in California, indoor/outdoor, and not vaccinated. Cat presented for severe URD unresponsive to antibiotics with pyrexia (103°F) and not eating. The submandibular lymph nodes are severely enlarged and aspirated thick yellow mucus from both; other lymph nodes WNL. URD panel declined. FeLV/FIV: Negative/negative; FCoV antibody by IFA: Positive @ 1:3200. No obvious retropharyngeal polyp seen.

The DVM submitted slides from left and right submandibular lymph nodes and all slides are similar.

20X
50X
100X
Click here for the IDEXX Pathology Report on this case.

Microscopic Description:

Slides are highly cellular and consist of inflammatory cells in a blue tissue fluid background with mild blood. Inflammatory cells consist predominantly of small to intermediate sized to occasionally large lymphocytes with moderately lesser numbers of variably vacuolated macrophages, few non-degenerate neutrophils and plasma cells. Macrophages are occasionally noted phagocytizing erythrocytes. Admixed are marked numbers of intra- and extracellular fungal yeast organisms. These organisms are variable sized, round to oval to fusiform, granular, and stain pink to blue with an occasional visible thin clear capsule. Narrow based budding is frequently noted. No overtly neoplastic cells are seen.

Cytologic Interpretation:

Pleomorphic lymphoid population with neutrophilic and histiocytic inflammation with marked numbers of fungal organisms consistent with Cryptococcus spp.

Comments/Pathogenesis:

The description of the lesion location and the presence of a lymphoid and plasma cell population on the submitted slides indicates lymph node involvement and; therefore, disseminated disease most likely from the upper respiratory infection. The morphology of the fungal organisms (round, variably sized, poorly capsulated, rare narrow based budding) is consistent with Cryptococcus spp.

Cryptococcus spp. infections are noted in humans and animals worldwide. These organisms are dimorphic fungi (typically yeast in vivo and hyphae in the environment). The two most common species include C. neoformans and C. gattii although 37 other species are known.

Cryptococcosis is a common fungal infection causing chronic upper respiratory tract disease in cats. Inhalation is the suspected route of infection and infectious particles have been isolated from pigeon guano and soil. Ocular, cutaneous and neurologic disease may be present concurrently with rhinitis via hematogenous or lymphatic spread. The prognosis is good to excellent for resolving early or mild cryptococcosis in immunocompetent patients with long term antifungal therapy; however, relapses may occur.

On cytology Cryptococcus spp. typically have a characteristic thick clear to pale staining mucopolysaccharide capsule and are readily identified. With some variants (including this case) there is a distinct lack of a thick capsule (i.e., poorly capsulated or “rough coated”) which may be more difficult to recognize and/or identify especially if there are few organisms present. Other diagnostic methods for identification include fungal culture, serology, PCR, and tissue biopsy with histopathology. PCR and fungal cultures may also be used for speciation.

100X Narrow-based budding highlighted
100X Reference image for comparison of Cryptococcus spp. with the more characteristic thick mucopolysaccharide capsule highlighted

Reference/Additional Information:

Sykes JE, Malik R. Cryptococcosis. In Greene CE, ed. Infectious diseases of the dog and cat. 4th ed. St. Louis: Elsevier, 2012: 621-634.

 

 

 

 

 

 

Leave a Reply