Original article
The predictive value of imaging studies in evaluating regional lymph node involvement in Merkel cell carcinoma

Preliminary data in this manuscript were presented as a poster at the Annual Meeting of the American College of Mohs Surgery, New York, New York, May 1, 2010.
https://doi.org/10.1016/j.jaad.2012.03.018Get rights and content

Background

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine malignancy with high potential for nodal or distant metastatic spread. Little information exists on sensitivity and specificity of various imaging techniques when compared with the gold standard of histopathologic evaluation of the lymph node basin.

Objective

We sought to further understand the value of various imaging modalities in the staging and initial workup of patients with MCC.

Methods

Of 240 patients with primary MCC evaluated between 1981 and 2008, 99 had diagnostic imaging at initial presentation with biopsy-proven cutaneous MCC and had histopathologic nodal evaluation within 4 weeks of the initial scan. We conducted a retrospective chart review of these identified patients.

Results

Computed tomography (n = 69) demonstrated a sensitivity of 47%, specificity of 97%, positive predictive value of 94%, and negative predictive value of 68% in detecting nodal basin involvement. Fluorine-18-fluorodeoxyglucose positron emission tomography scan (n = 33) demonstrated a sensitivity of 83%, specificity of 95%, positive predictive value of 91%, and negative predictive value of 91% in detecting nodal basin involvement. Magnetic resonance imaging (n = 10) demonstrated a sensitivity of 0%, specificity of 86%, positive predictive value of 0%, and negative predictive value of 67% in detecting nodal basin involvement.

Limitations

This was a retrospective study with small sample size.

Conclusion

Use of fluorine-18-fluorodeoxyglucose positron emission tomography in the evaluation of a regional lymph node basin in primary MCC is significantly more sensitive and equally specific when compared with traditional computed tomography. Both fluorine-18-fluorodeoxyglucose positron emission tomography and computed tomography are more sensitive than clinical examination alone.

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

References (17)

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Funding sources: None.

Conflicts of interest: None declared.

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