Unseen Aggressor: A Case of Amelanotic Melanoma With Orbital Metastasis and Imaging-Pathology Correlation

Amelanotic melanoma represents an uncommon and aggressive variant of cutaneous melanoma. The characteristic absence of pigmentation poses significant diagnostic challenges, frequently leading to delayed clinical recognition and unfavorable prognosis compared to conventional pigmented melanomas. We report a 57-year-old Caucasian male patient with a medical history of amelanotic melanoma of the right foot surgically treated in 2010. The patient subsequently lost medical follow-up and presented 13 years later with nonspecific left upper quadrant abdominal pain. Comprehensive evaluation revealed extensive metastatic disease involving multiple organ systems. Chest computed tomography demonstrated bilateral pulmonary nodules with characteristic "cannonball" morphology, while brain magnetic resonance imaging revealed multiple intraparenchymal lesions with surrounding vasogenic edema. Physical examination disclosed multiple erythematous cutaneous nodules on the thorax and extremities, bilateral lymphadenopathy, and hepatosplenomegaly. Dermoscopic examination of cutaneous lesions revealed pathognomonic "milky-red areas" and polymorphous atypical vascular patterns, including irregular linear, dotted, and corkscrew vessels. Histopathological analysis of a cervical lymph node biopsy confirmed metastatic epithelioid amelanotic melanoma, with immunohistochemistry demonstrating positive staining for S100, Melan-A, and CDX10, while cytokeratin AE1/AE3 was negative. This case exemplifies the unpredictable biology of amelanotic melanoma, an uncommon and aggressive variant of cutaneous melanoma. Underscoring the critical importance of lifelong dermatological surveillance, advanced imaging techniques, and dermoscopic evaluation in managing this aggressive malignancy. Contemporary immunotherapy and targeted therapies offer significant therapeutic advances for patients with advanced metastatic disease, emphasizing the need for multidisciplinary management and sustained clinical vigilance in optimizing patient outcomes.