Clinical benefit of baseline imaging in Merkel cell carcinoma: Analysis of 584 patients

J Am Acad Dermatol. 2021 Feb;84(2):330-339. doi: 10.1016/j.jaad.2020.07.065. Epub 2020 Jul 21.


Background: Merkel cell carcinoma (MCC) guidelines derive from melanoma and do not recommend baseline cross-sectional imaging for most patients. However, MCC is more likely to have metastasized at diagnosis than melanoma.

Objective: To determine how often baseline imaging identifies clinically occult MCC in patients with newly diagnosed disease with and without palpable nodal involvement.

Methods: Analysis of 584 patients with MCC with a cutaneous primary tumor, baseline imaging, no evident distant metastases, and sufficient staging data.

Results: Among 492 patients with clinically uninvolved regional nodes, 13.2% had disease upstaged by imaging (8.9% in regional nodes, 4.3% in distant sites). Among 92 patients with clinically involved regional nodes, 10.8% had disease upstaged to distant metastatic disease. Large (>4 cm) and small (<1 cm) primary tumors were both frequently upstaged (29.4% and 7.8%, respectively). Patients who underwent positron emission tomography-computed tomography more often had disease upstaged (16.8% of 352), than those with computed tomography alone (6.9% of 231; P = .0006).

Limitations: This was a retrospective study.

Conclusions: In patients with clinically node-negative disease, baseline imaging showed occult metastatic MCC at a higher rate than reported for melanoma (13.2% vs <1%). Although imaging is already recommended for patients with clinically node-positive MCC, these data suggest that baseline imaging is also indicated for patients with clinically node-negative MCC because upstaging is frequent and markedly alters management and prognosis.

Keywords: CT; MCC; Merkel cell carcinoma; PET-CT; SLNB; baseline imaging; clinical guidelines; distant metastasis; melanoma; nodal metastasis; nonmelanoma skin cancer; occult disease; scans; sentinel lymph node biopsy; skin cancer; staging.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Biopsy / statistics & numerical data
  • Carcinoma, Merkel Cell / diagnosis*
  • Carcinoma, Merkel Cell / secondary
  • Carcinoma, Merkel Cell / therapy
  • Child
  • Female
  • Humans
  • Lymph Nodes / diagnostic imaging*
  • Lymph Nodes / pathology
  • Lymphatic Metastasis / diagnosis*
  • Lymphatic Metastasis / therapy
  • Male
  • Middle Aged
  • Neoplasm Staging / standards
  • Neoplasm Staging / statistics & numerical data
  • Positron Emission Tomography Computed Tomography / standards
  • Positron Emission Tomography Computed Tomography / statistics & numerical data*
  • Practice Guidelines as Topic
  • Predictive Value of Tests
  • Prognosis
  • Retrospective Studies
  • SEER Program / statistics & numerical data
  • Skin Neoplasms / diagnosis*
  • Skin Neoplasms / pathology
  • Skin Neoplasms / therapy
  • Young Adult