Merkel Cell Carcinoma, Skin



Merkel Cell Carcinoma, Skin


Nayela Keen, MD

Christine M. Glastonbury, MBBS









(Left) Clinical photograph demonstrates subtle, small lesion of midline face, just above the upper lip image, which at biopsy proved to be Merkel cell carcinoma. Also notice marked fullness of left lower cheek image. (Right) Axial CECT in same patient with skin marker demonstrates enlarged left facial node image without necrosis or calcifications. This corresponds to lower left cheek palpable and visible mass. Additional small bilateral submandibular nodes were also evident on this CECT.






(Left) Axial T2WI FS MR in same patient obtained almost 4 weeks after initial CT shows marked increase in size of left facial node image without necrosis. Case well illustrates the potential for rapid growth of Merkel cell carcinoma. (Right) Axial fused PET/CT obtained 1 week prior to MR shows avid FDG uptake in small left submandibular node image and large right IB node image. Larger left facial node shown on CT above and MR to left was also markedly FDG avid (SUV = 15).



TERMINOLOGY


Abbreviations



  • Merkel cell carcinoma (MCC)


Synonyms



  • Neuroendocrine carcinoma of skin


Definitions



  • Neuroendocrine skin malignancy derived from Merkel cells



    • Part of the mechanoreceptor complex in skin


    • Located at basal layer of epidermis


    • Probably derived from neural crest cells


IMAGING


General Features



  • Best diagnostic clue



    • Nodal mass within neck associated with possible focal skin thickening



      • Primary site may be subtle clinically as well as radiographically


  • Location



    • Most commonly arises on facial skin



      • 50% of cases occur in head and neck



        • Cheeks, nose, perioral, eyelids, periocular


      • 30% occur on extremities


      • 5-7% occur on trunk


      • < 15% unknown primary site


      • Even more rarely arises from mucosal surfaces


  • Size



    • Median diameter of primary at diagnosis = 1.1 cm


    • May present from adenopathy without discernible primary


  • Morphology



    • If primary visible, appears as exophytic subcutaneous nodule


CT Findings



  • CECT



    • Primary: Skin thickening or subcutaneous mass


    • Solid nodal disease, moderately enhancing


MR Findings



  • Primary site is typically small and may not be evident on imaging


  • If lesion seen, typically T2 hyperintense and moderately to markedly enhances with contrast


  • May see abnormal adjacent nodularity or hyperintensity of subcutaneous fat to suggest intralymphatic spread


  • Involved nodes of variable size, typically solid and moderately enhance with contrast


Nuclear Medicine Findings



  • PET/CT



    • Merkel cell carcinoma is highly FDG avid



      • Useful for staging, surveillance, restaging recurrent disease and distant metastasis


      • Even small nodes may show increased FDG uptake


  • Lymphoscintigraphy may be used to locate sentinel nodes



    • Increasingly important role in MCC treatment


Imaging Recommendations

Sep 20, 2016 | Posted by in HEAD & NECK IMAGING | Comments Off on Merkel Cell Carcinoma, Skin
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