PMC10141254_01
Right forelimb with a nodular lesion, 7 mm in diameter, cutaneous to subcutaneous,
pigmented, soft, haired, non-painful and non-productive
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The lesion was 7 mm in diameter, cutaneous to subcutaneous, pigmented, soft, haired, non-painful and non-productive (Figure 1).
Fine-needle aspire of the nodule. Damaged inflammatory cells suggestive of neutrophils
and multiple pigmented fungal elements (arrows point to May-Grunwald-Giemsa staining,
magnification x 1000)
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Cytological examination revealed damaged inflammatory cells suggestive of neutrophils and the presence of multiple pigmented fungal elements, leading to a diagnosis of phaeohyphomycosis without precise identification of the fungal species involved (Figure 2).
Plaque-like lesion located in the interorbital region
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On the day of the surgery, 1 month after the initial presentation, the nodule was slightly larger (approximately 1 cm in diameter), and a pigmented plaque-like lesion had appeared between the eyes (Figure 3).
Histopathological examination of the nodule removed from (a) the right forelimb and (b)
the biopsy of the plaque-like interorbital lesion, showing a nodular-to-diffuse
superficial and deep dermal dermatitis (haematoxylin and eosin staining,
magnification x 40, bars = 1000 mum [a] and 500 microm [b]). (c) The infiltrate was
histiocytic, lymphocytic and, to a lesser extent, neutrophilic, with numerous spherical
elements, 3-20 microm in diameter, often isolated or with narrow-based buds, pigmented,
surrounded by a basophilic capsule (black arrows, haematoxylin and eosin staining,
magnification x 400, bar = 10 mum). (d) Periodic acid-Schiff staining showed that the
elements were positive (magnification x 400, bar = 10 mum)
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Microscopic appearance was similar for both lesions and was characterised by diffuse, superficial and deep dermal (Figure 4a,b) histiocytic, lymphocytic and, to a lesser extent, neutrophilic infiltrate, with numerous spherical elements, measuring 3-20 microm in diameter, often isolated or with narrow-based buds, surrounded by a basophilic capsule (Figure 4c). Periodic acid-Schiff staining revealed that the elements were positive (Figure 4d).
(a) Appearance of the fungal colonies after incubation on Sabouraud dextrose agar for
11 days at 37 C. The colonies were black, slimy at the centre due to yeast-like growth
and smooth near the margin. (b) Microscope images (x 400 magnification) of the fungus.
Brownish septate hyphae and numerous conidia (some with annellated zones, representing
germinating cells) are visible
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The fungus was cultured on Sabouraud dextrose agar plates complemented with 0.5 g/l chloramphenicol for 11 days at 27 C and 37 C and yielded colonies of a black yeast-like fungus (Figure 5).