Cutaneous fungal granuloma in a cat

Fine needle aspirate from a nodular cutaneous mass on the nasal planum of a cat.

Figure 1. The predominant cell population consists of macrophages and multinucleated giant cells mixed with fewer neutrophils. Within the mixed inflammatory infiltrate are numerous fungal organisms characterised by septate hyphae (red arrow) with globose dilatations forming spore-like structures (black arrow).
Figure 2. Many of the fungal organisms (red arrows) have been phagocytosed by multinucleated giant cells (black arrow).


Granulomatous inflammation associated with fungal infection (fungal granuloma)


This is most likely a case of phaeohyphomycosis, an opportunistic fungal infection caused by ubiquitous saprophytes or plant pathogens. These fungi typically produce pigmented fungal hyphae in mammalian tissue, although the pigment is not evident in routinely prepared cytological specimens. The disease most commonly manifests as a primary cutaneous or subcutaneous infection and lesions are mostly found on the distal extremities, particularly the nasal planum of cats. Histopathology and fungal culture are required for definitive diagnosis. Treatment includes complete surgical excision (where possible) with/without systemic antifungal therapy.