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Updated: Sep 5, 2025
Merkel Cell Polyomavirus Infection and Detection
Published on: February 7, 2019
Merkel cell carcinoma of unknown primary: Clinical presentation and outcomes
Samuel E Broida1, Xiao T Chen1, Christian L Baum2
1Department of Orthopaedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
Background:
Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous malignancy that usually occurs in the head/neck or extremities. However, there are reports of MCC developing in the lymph nodes or parotid gland without evidence of a primary cutaneous lesion.
Methods:
We reviewed 415 patients with biopsy-proven MCC. Patients with MCC of unknown primary (n = 37, 9%, MCCUP) made up the study cohort. The primary endpoints of the study were rate of recurrence, disease-free survival, and overall survival.
Results:
Patients with MCCUP presented with tumors in lymph nodes (n = 34) or parotid gland (n = 3). Nodal disease was most commonly detected in the inguinal/external iliac (n = 15) or axillary (n = 14) regions. The mean age at diagnosis was 70 years and 24% were female. Patients presented with distant metastases in 24.3% of cases. Patients with stage IIIA disease treated with regional lymph node dissection (RLND) had a lower risk of disease recurrence (hazard ratio 0.26, p = 0.046). Recurrence-free survival was 59.3% at 5 years. Disease-specific survival was 63.3% at 5 years.
Conclusion:
Patients with MCCUP have a high risk of recurrence and mortality. The optimal treatment for MCCUP has yet to be elucidated, although therapeutic RLND appears beneficial for these patients.
