Metastatic Melanoma of Unknown Primary Site

Rodrigo Arrangoiz MS, MD, FACS, FSSO
  • Approximately 1% to 8% of patients with melanoma:
    • Present with metastatic disease from melanoma of unknown primary (MUP) site
  • The most common presentation is:
    • In the axillary lymph node basin (> 50%):
      • Followed by the cervical lymph node basin
  • Various reasons have been proposed for the phenomenon of MUP site:
    • Anbari et al. suggested the following possibilities for primary lesions:
      • An unrecognized melanoma
      • A treated melanoma that had been initially misdiagnosed
      • A spontaneously regressed melanoma
      • Malignant transformation of a melanocyte that had traveled to a metastatic location
  • For metastatic melanoma to be classified as MUP site:
    • The histologic diagnosis must be confirmed
    • Previous biopsies and / or excisions, if any, should be evaluated for a possible diagnosis of melanoma
    • Less common primary sites for melanoma should be thoroughly evaluated
  • A thorough history may also identify prior lesion that was excised or destroyed:
    • But never pathologically examined
  • If the metastatic lesion is to a lymph node basin:
    • The drainage areas of that basin should be rigorously examined
    • Furthermore, patients should undergo staging evaluation with:
      • CT of the chest, abdomen, and pelvis (also including neck CT if anatomically appropriate), and MRI of the brain
      • PET / CT can also be considered, particularly in the setting of extremity soft tissue metastasis associated with unknown primary
  • Several studies have compared the survival of these patients to similar cohorts having equivalent nodal status and a known primary site:
    • Although patients with unknown primary tumors were historically believed to have worse prognoses:
      • Recent studies have contradicted earlier findings by demonstrating that patients with MUP have a natural history that is similar to (if not better than) the survival of many patients with stage III disease:
        • Given their survival profile, such patients with nodal disease should be staged as stage III and treated like stage III patients with a known primary melanoma, including consideration for stage III clinical trials
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Published by Rodrigo Arrangoiz MS, MD, FACS, FSSO

My name is Rodrigo Arrangoiz I am a breast surgeon/ thyroid surgeon / parathyroid surgeon / head and neck surgeon / surgical oncologist that works at Center for Advanced Surgical Oncology in Miami, Florida. I was trained as a surgeon at Michigan State University from (2005 to 2010) where I was a chief resident in 2010. My surgical oncology and head and neck training was performed at the Fox Chase Cancer Center in Philadelphia from 2010 to 2012. At the same time I underwent a masters in science (Clinical research for health professionals) at the University of Drexel. Through the International Federation of Head and Neck Societies / Memorial Sloan Kettering Cancer Center I performed a two year head and neck surgery and oncology / endocrine fellowship that ended in 2016. Mi nombre es Rodrigo Arrangoiz, soy cirujano oncólogo / cirujano de tumores de cabeza y cuello / cirujano endocrino que trabaja Center for Advanced Surgical Oncology en Miami, Florida. Fui entrenado como cirujano en Michigan State University (2005 a 2010 ) donde fui jefe de residentes en 2010. Mi formación en oncología quirúrgica y e n tumores de cabeza y cuello se realizó en el Fox Chase Cancer Center en Filadelfia de 2010 a 2012. Al mismo tiempo, me sometí a una maestría en ciencias (investigación clínica para profesionales de la salud) en la Universidad de Drexel. A través de la Federación Internacional de Sociedades de Cabeza y Cuello / Memorial Sloan Kettering Cancer Center realicé una sub especialidad en cirugía de cabeza y cuello / cirugia endocrina de dos años que terminó en 2016.

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