Neoadjuvant therapy with vemurafenib in Horner's syndrome as a very rare first diagnosis of a malignant melanoma of unknown primary

We report on a 54-year-old female patient who presented at our oncological outpatient department in 2012. The patient initially complained about ptosis of the right eye and severe right thoracic pain. A Horner's syndrome was suspected, although additional typical symptoms such as miosis and anhidrosis were missing. For further diagnostic imaging the patient underwent a chest MRI. MRI showed a tumor at the apical segment of the upper lobe of the right lung (Pancoast tumor) as well as enlarged right hilar and mediastinal lymph nodes (Figure 1). PET-CT and MRI of the brain revealed no evidence of metastases. A biopsy was performed to determine the characteristics of the tumor. The pathology result showed a metastasis of a malignant melanoma. No primary site was detected by clinical examination of the skin. The patient was diagnosed with stage IV M1b melanoma of unknown primary (CUP). Tissue-based analysis identified a V600E mutation. As the patient was initially inoperable, systemic treatment with the BRAF inhibitor vemurafenib was initiated. Combination with an MEK inhibitor was not yet approved in 2012. After twelve weeks of therapy, a partial response was detected and the decision for surgery was made (Figure 2). Due to remission with neoadjuvant treatment, the entire tumor mass could be resected (Figure 3). The postoperative course was uncomplicated. Adjuvant treatment was not given. No relapse occurred during six years of follow-up. Five Percent of newly diagnosed cases of malignant melanoma are classified as melanomas of unknown primary (CUP). In rare cases the primary lesion is located in the ear, eye, urethra or intestinal mucosa [1]. However, the most favored assumption is immune-mediated degradation of the primary site, while metastases are not affected [2]. DOI: 10.1111/ddg.13983 Neoadjuvant therapy with vemurafenib in Horner's syndrome as a very rare first diagnosis of a malignant melanoma of unknown primary Clinical Letter