Malignant skin adnexal tumor of the finger with late metastases

Malignant cutaneous adnexal tumors (MCATs) are rare neoplasms with unpredictable metastatic behavior and limited radiologic characterization. We report a case of malignant spiradenocylindroma initially evaluated with ultrasound, which demonstrated a pear-shaped heterogeneous subcutaneous structure with slight peripheral hyperemia and a small fluid-filled component in the distal phalanx of the left third finger, interpreted as a possible post-traumatic hematoma or foreign-body reaction consistent with the clinical history. Three years later, magnetic resonance imaging (MRI) revealed an infiltrative, contrast-enhancing mass with adjacent bone destruction, confirming a malignant process. After amputation, the patient remained disease-free for 8 years before developing neurological symptoms. Brain MRI showed an unusual multilobulated cystic metastasis, and positron emission tomography combined with computed tomography (PET/CT) demonstrated metabolically active pulmonary metastases. The patient ultimately experienced a fatal outcome. This case highlights the diagnostic challenges in early presentation and underscores the potential for delayed distant metastases in MCATs while expanding the radiologic spectrum of intracranial involvement to include rare multilobulated cystic presentations.