Pseudotumorous Lesion of the Scalp Revealing Actinomycosis Mycetoma: Case Report with Review of the Literature

Introduction: Mycetoma is an inflammatory pseudotumor localized to the subcutaneous tissue, containing fungal granules of fungal origin, or actinomycosis due to filamentous bacteria. Although the gold standard diagnosis is mycology, it gives rise to a specific granulomatous inflammation. From this perspective, histopathology can predict whether it is a mycosis or an actinomycosis, based on the characteristics of the granules, particularly their color. It is mainly found on the foot. Although rare, extrapodal localisations have been reported. We present a case of incidental discovery during the histopathological study of a multifocal pseudotumoral lesion of the scalp, with a review of the literature. Case Report: A 16 years old woman presented with three fistulized nodules of the scalp evolving for approximately one year with febrile episodes. Biopsies performed in response to the pseudotumoural nature of the lesion revealed a granulomatous inflammatory infiltrate composed of epithelioid histiocytes, Langhans-like giant cells and foreign bodies surrounding areas of suppurative necrosis, centered by peripheral red, club-shaped granules containing numerous filaments, suggesting actinomycotic mycetoma. Conclusion: Although rare, extrapodal actinomycotic mycetoma is nevertheless observed. The case we reported involved the scalp and pseudotumoral lesions. It highlights the importance of histopathology in inflammatory pathology, particularly mycotic pathology, in a context where mycological examination is sometimes unavailable.