Mesenteric cryptococcal granuloma in a dog caused by Cryptococcus neoformans var. grubii

Abstract

Although cryptococcosis is usually associated with respiratory and neurologic signs in domestic species (such as sneeze, cough, nasal discharge, seizures, ataxia), clinical manifestations of the disease may be more subtle and nonspecific. A 3-year-old male castrated Boxer dog presented with a history of chronic vomiting, diarrhea, weight loss, and lethargy. At no time had respiratory or neurologic signs been noted by the owners or the primary care veterinarian. Palpation of an abdominal mass revealed an atypical lesion location: a large (16 × 9 × 7 cm) mass at the root of the mesentery. Diagnosis was achieved through cytology of this mass and a positive serologic Cryptococcus capsular antigen titer; polymerase chain reaction was utilized for speciation of the abdominal isolate as Cryptococcus neoformans variety grubii. The animal was euthanized due to poor prognosis. After necropsy and histopathologic analysis, the mesenteric mass and associated lymph nodes were identified as large fungal granulomas. This is a rare manifestation of cryptococcosis, involving several visceral organs, with no remaining evidence of the route of entry of the organism. As prompt diagnosis of mycotic illness is paramount to successful management, this case indicates that cryptococcal infection should be considered as a differential diagnosis in dogs with gastrointestinal signs and lymphadenopathy. The protean nature of cryptococcosis is discussed within the context of a brief review of emerging and unresolved issues in pathogenesis.

Keywords: Cryptococcus gattii; granuloma; lymphadenitis.

Figure 1

Fine-needle aspirate cytology of a cranial abdominal mass displaying numerous extracellular and intrahistiocytic Cryptococcus spp. yeasts with prominent nonstaining capsules, narrow-based budding (arrow), and occasional chains of organisms. Notes: Modified Wright’s stain (Diff-Quik^®). 60× objective. Bar = 20 μm.

Figure 2

Gross necropsy photograph of intestinal tract with large cryptococcal lesion (demarcated by arrows) adhered to the root of the mesentery.

Figure 3

Histologic section of mesenteric lymph node with histiocytic inflammation and extracellular cryptococcal yeast organisms (pink). Notes: Mucicarmine stain. Bar = 20 μm.