Metastatic Melanoma to the Orbit With Dedifferentiation: A Case Report.

We present the first documented case of metastatic melanoma to the orbit with dedifferentiation. A patient with a history of melanoma of the lip and other poorly differentiated carcinomas presented with both a sub-brow and an intraorbital mass. Radiographically and intraoperatively, the sub-brow mass communicated with the intraorbital mass via perineural spread along the supraorbital nerve. Histopathology confirmed the diagnosis of melanoma based on the melanocytic markers, SOX-10 and Melan-A; dedifferentiation was demonstrated within the orbital tumor. Two weeks following surgical debulking, the intraorbital mass returned to its full size. Local radiotherapy and immunotherapy were performed, which initially led to a dramatic improvement; however, the patient succumbed to his systemic metastases six months later. Dedifferentiation serves as a prognostic indicator and should be considered in patients when histopathology does not lead to a definitive diagnosis.