Atypical Fibroxanthoma of the Thigh in a 12-Year-Old Adolescent: A Case Report / 대한피부과학회지

ABSTRACT

Atypical fibroxanthoma (AFX) is a rare fibrohistiocytic tumor usually observed on ultraviolet light-exposed areas of the body, such as the face or scalp in elderly individuals. Despite its clinically benign course, AFX presents with malignant features on histopathological evaluation. A 12-year-old male adolescent presented with a 3-month history of an asymptomatic, skin-colored, oval-shaped nodule on his right thigh. Histopathological examination showed a dermal tumor adjacent to the epidermis, without epidermal invasion. The tumor was composed of numerous pleomorphic spindle cells and large atypical histiocytes with abundant vacuolated cytoplasm and pleomorphic nuclei. Immunohistochemical analysis revealed tumor cells, which were immunopositive for vimentin, CD68, CD10 and immunonegative for desmin, pan-cytokeratin antibody (AE1/AE3), and S-100. Therefore, the patient was diagnosed with AFX. We report a rare case of AFX that occurred on the thigh (an unusual site) in an adolescent (an uncommon age group). Immunohistochemical analysis is important in patients with suspected AFX, regardless of the patient’s age and site of lesion, for accurate diagnosis to differentiate this condition from other diseases with a similar presentation.