Diagnostic challenge of aneurysmal dermatofibroma mimicking cutaneous metastasis in a patient with lung cancer: A case report.

While cutaneous metastasis from lung cancer is rare, its recognition is critical. Benign mimics like aneurysmal dermatofibroma (ADF) complicate diagnosis, particularly in patients with known malignancy. A 71-year-old man with non-small cell lung cancer presented with a chest wall nodule. Positron emission tomography-CT revealed hypermetabolic activity (maximum standardized uptake volume, 6.9), prompting excision. Histopathology showed spindle-like cells in storiform patterns, blood-filled spaces and CD34/human herpesvirus-8 negativity. Ki-67 (5%) confirmed ADF. This case illustrates the diagnostic challenge of distinguishing ADF from cutaneous metastasis in patients with known malignancy. Improper workup through imaging or clinical impression without pathologic confirmation may lead to unsuitable treatment. Histologic confirmation with immunohistochemical assessment is essential for accurate diagnosis. ADF as a potential mimic of metastatic disease is necessary to prevent upstaging. Histopathological confirmation should always be considered for ambiguous cutaneous lesions.