Original articleThe predictive value of imaging studies in evaluating regional lymph node involvement in Merkel cell carcinoma
Section snippets
Methods
Approval of the Mayo Clinic Institutional Review Board was obtained for a multicenter, retrospective review of a consecutive series of patients who received a diagnosis of known primary MCC between January 1981 and December 2008 at Mayo Clinic's 3 sites (Minnesota, Arizona, and Florida). Included in the study was the subset of patients who had histopathologic nodal evaluation with either SLNB or regional LND (elective or therapeutic), or both. Histopathologic confirmation of node-negative or
Results
We identified 240 patients with known primary MCC diagnosed between January 1981 and December 2008 (Fig 1). Among them, 120 patients had primary cutaneous MCC with histopathologic nodal evaluation with either SLNB or regional LND, or both. Of these 120 patients, 99 met the criteria of having diagnostic imaging (eg, CT, MRI, F-18-FDG–PET) at initial presentation with biopsy-proven cutaneous MCC and then went on to have histopathologic nodal evaluation within 4 weeks of the initial scan.
Discussion
The optimal imaging method for staging primary MCC continues to be unclear. Data are limited on the sensitivity of imaging using the gold standard of histopathologic confirmation. Previous studies by Gupta et al13 using this gold standard showed CT to have a sensitivity of about 20% for detecting MCC that had spread to the lymph node basin. Their study also showed a low specificity for distant disease, with only 4 of 21 “positive” scans confirmed for disease during 6 months of follow-up. The
Conclusion
This study was the largest to date of various imaging methods in the evaluation of regional lymph node basins in MCC with the gold standard histopathologic confirmation. Our data support the use of F-18-FDG–PET over standard CT and MRI alone when imaging the regional lymph nodal basin. Given previous studies showing the effectiveness of F-18-FDG–PET/CT and F-18-FDG–PET in evaluating distant metastatic disease, F-18-FDG–PET should be the radiologic test of choice when clinicians decide to pursue
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Funding sources: None.
Conflicts of interest: None declared.