Immunostaining for Cytokeratin 20 Improves Detection of Micrometastatic Merkel cell Carcinoma in Sentinel Lymph Nodes.


BACKGROUND: Sentinel lymph node biopsy (SLNBx) can identify Merkel cell carcinoma (MCC) micrometastasis.

OBJECTIVE: We attempted to examine the effectiveness of immunostaining and identify antibodies most appropriate for evaluation of SLNBxs for MCC.

METHODS: Histopathologic material from 10 patients with MCC who had SLNBx was reviewed.

RESULTS: Twenty-three SLNBxs from 10 patients appeared tumor-free in routine hematoxylin-eosin (H&E)-stained sections. However, tumor cells were detected in immunostained sections from 5 (22%) of 23 SLNBxs in 4 (40%) of 10 patients. Immunostains with pancytokeratin (panCK), cytokeratin-20 (CK-20), neurofilament protein, and chromogranin A were used for all primary and SLNBx specimens. All 5 (100%) micrometastatic foci stained strongly for CK-20 and panCK. Background normal lymph node tissue also stained for panCK but not for CK-20.

CONCLUSION: Examination of H&E sections alone is insufficient for excluding micrometastatic MCC in sentinel lymph nodes. We observed the greatest sensitivity and specificity with anti-CK-20 antibody in identifying micrometastatic MCC in sentinel lymph nodes.

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Journal of the American Academy of Dermatology

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