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Abstract

Adult xanthogranuloma, a variant of non-Langerhans Cell Histiocytosis, shares histopathological features with Juvenile Xanthogranuloma, characterized by the accumulation of foamy histiocytes and inflammatory cells within diverse tissue compartments. The head and neck region typically represent the most frequently reported site, whereas foot localization is notably uncommon. In this instance, we present an exceptional case of adult-onset Xanthogranuloma with localization to the foot with no accompanying systemic or other cutaneous lesions. 

A 43-year-old male presented with a progressively enlarging firm lesion on the medial aspect of the left foot over two years. Clinical examination revealed a non-tender circular pink nodule measuring 2.00 x 2.00 x 0.60 cm with a conspicuous vascular pattern. Histopathological assessment demonstrated epidermal attenuation with rete ridge loss, alongside a dense dermal infiltrate comprising foamy histiocytes, scattered Touton giant cells, lymphocytes, plasma cells, and occasional eosinophils. Immunohistochemical analysis revealed negativity for S100 and CD1a, consistent with a diagnosis of xanthogranuloma. 

While typically encountered in infancy, xanthogranuloma in adults is a rare occurrence, emerging in the third or fourth decade of life. Adult presentations often differ, with solitary lesions more commonly observed on the face, although multiple lesions, particularly in males, can also manifest. Distinguishing features from Erdheim-Chester disease include the lack of extracutaneous involvement. In some instances, multiple xanthogranulomas might indicate underlying hematological disorders. 

Treatment modalities encompass surgical excision, CO2 laser therapy, or systemic therapies. Due to the unpredictable nature of disease progression, vigilant monitoring is advisable.