Right Thumb Mycetoma: A Case Report and Review of the Literature.

Mycetoma, or maduromycosis, is a chronic granulomatous infection involving the skin, subcutaneous tissues, and bones, most commonly affecting the lower extremities. Hand involvement is rare and often leads to diagnostic delays due to its atypical presentation. Mycetoma is classified as actinomycetoma (bacterial) or eumycetoma (fungal), each requiring distinct management approaches. We report a rare case of actinomycetoma affecting the right thumb in an 81-year-old man, initially misdiagnosed as a giant cell tumor. Magnetic resonance imaging revealed a well-defined subcutaneous mass without bony involvement. Surgical excision was performed, and histopathology confirmed actinomycetoma, showing filamentous bacterial colonies with neutrophilic infiltrates. The patient was treated with a 3-month course of trimethoprim/sulfamethoxazole and remained recurrence-free at 12 months. This case highlights the importance of including infectious etiologies in the differential diagnosis of chronic hand masses, particularly in nonendemic regions. Early recognition, accurate microbiological classification, and tailored treatment are critical to preventing recurrence and preserving function.