Baseline ultrasound and FDG-PET/CT imaging in Merkel cell carcinoma

December 28, 2022


Journal of Surgical Oncology

Publication Date

December 28, 2022


Lisanne P. Zijlker, Max Bakker, Bernies van der Hiel, Annemarie Bruining, W. Martin C. Klop, Charlotte L. Zuur, Michel W. J. M. Wouters, Alexander C. J. van Akkooi Summary

At the time of diagnosis, MCC is known to have spread from the primary site to other locations in over one third of cases. The best way to detect such spread is still debated, but major guidelines now suggest that a PET-CT scan is one preferred method. In this study, the authors analyzed 135 MCC patients from the Netherlands. They found that either PET-CT or ultrasound-guided biopsy detected spread to nearby lymph nodes frequently (~20%) in patients whose nodes were normal by physical examination. Among those with abnormal/enlarged lymph nodes, PET-CT found evidence of distant spread in the body in 16% of cases. This study supports the need for careful imaging of MCC patients to properly stage and initially manage their care.



Merkel cell carcinoma (MCC) is a cutaneous tumor with a high tendency to metastasize, and a significant proportion of patients have metastases at first presentation. This study aims to determine the value of baseline ultrasound (US) and 18fluorodeoxyglucose-positron emission tomography/computed tomography (18FDG-PET/CT) imaging in both patients with clinically localized MCC (Stage I/II) and patients who present with palpable lymph nodes (Stage III).


This retrospective cohort included 135 MCC patients who underwent baseline US (with fine needle aspiration cytology (FNAC)) and/or FDG-PET/CT imaging between 2015 and 2021.


Of the 104 patients with clinically localized disease, 48% were upstaged to Stage III and 3% to Stage IV by imaging or sentinel lymph node biopsy (SLNB). FDG-PET/CT imaging identified regional metastases in 23%, while US with FNAC identified regional metastases in 19%. SLNB was performed in 56 patients, of whom 57% were upstaged to Stage III. Of the 31 patients who presented with palpable lymph nodes, 16% were upstaged to Stage IV by FDG-PET/CT imaging.


Baseline imaging frequently upstages Stage I/II MCC patients to Stage III, both by US and FDG-PET/CT, Stage IV disease is rarely identified. Patients who present with palpable nodes are frequently upstaged to Stage IV by FDG-PET/CT imaging.

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