The role of histopathology in the diagnosis of dermatophytoses / Značaj patohistološkog nalaza u dijagnostici dermatofitoza

Histopathological analysis is not a routine procedure for diagnosing fungal skin infections. In the histopathological specimens, fungi are visible only when using special stain such as periodic acid-Schiff (PAS). However, histopathological analysis may not be performed in small laboratories. Histopathological characteristics of fungal skin infections are not specific. In all skin biopsy cases, obtained without clinical suspicion of fungal infection, the knowledge of certain, most frequent histopathological reaction patterns, as well as specific histopathological indicators (a diagnostic histopathological “clue”), of certain superficial mycoses e.g., dermatophytoses, may raise a suspicion of fungal infection and warrant a fungal-specific staining. A retrospective analysis of all PAS-stained sections was carried out. All PAS-positive biopsy specimens were assessed for clinical features, histopathological patterns of skin reactions, and presence of histopathological indicators. Our results have shown that out of the total of 361 PAS-stained sections, fungal hyphae were identified in 12 (3.3%) specimens. In 5 (1.4%) cases, the diagnosis of fungal infection was suspected on clinical grounds, while in 7 (1.9%) cases detection of fungi was an unexpected finding. The most frequent type of histopathological pattern was spongiotic, and the most frequent histopathological indicator was the presence of neutrophils within the epidermis. Our results confirm that dermatophytoses may present with clinical and histological non-specific findings. PAS staining represents a relatively cheap and simple fungal-specific staining. It has been suggested that it not only confirms that the selected material is actually invaded, but also reduces the number of false-negative direct reports, where fungi are cultured from a microscopically negative specimen. Apart from a small percentage of positive findings, our results justify the need for routine PAS staining of all clinically and histologically non-specific inflammatory skin conditions.