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Background: Dermatophytosis is sometimes difficult to definitively diagnose if it has atypical clinical characteristics or the mycological tests are negative. For these cases, skin biopsy will be helpful to diagnose a fungal infection. Objective: The purpose of the present study was to evaluate the clinical, histopathologic and mycologic characteristics of dermatophytosis patients who were initially diagnosed by skin biopsies. Methods: We performed a retrospective study of the clinical characteristics and the histopathologic and mycologic features of 16 patients with dermatophytosis and who were initially diagnosed by skin biopsy. Results: The final diagnosis of dermatophytic infections were tinea incognito (7 cases) and Majocchi’s granuloma (9 cases). The main symptoms were pruritus (4 cases) and pain (2 cases). The skin lesions of tinea incognito and Majocchi’s granuloma mimicked inflammatory skin disease, lupus vulgaris or deep mycosis. The most common site of involvement was the face. The possible predisposing factors causing tinea incognito and Majocchi’s granulomas appeared to be application of steroid ointment (6 cases), physical trauma (2 cases) and diabetes mellitus (1 case). The histopathologic features of tinea incognito revealed the sandwich sign (100%) and neutrophils in the epidermis (71.5%) and dermis (71.5%). Majocchi’s granuloma showed rupture of hair follicles (88.9%) and suppurative folliculitis (66.7%). With Periodic acid Schiff and methenamine silver staining, hyphae and spores could be identified on the horny layers, within the hair follicles and/or on the dermis in the biopsy specimens of all the cases. Culture of the causative organisms using dermal fragments and skin scales on Sabouraud media demonstrated Trichophyton rubrum (4 cases), T. mentagrophytes (3 cases) and Microsporum canis (3 cases). Systemic treatment with itraconazole or terbinafine for 2∼10 weeks was effective, except for two cases. Conclusion: We consider that the histopatholgic findings may be of great help to diagnose a dermatophytosis that has atypical clinical characteristics or negative mycological tests. Fungal culture is also important for making an accurate diagnosis of dermatophytosis.