Application of immunocytochemistry and BRAF mutational analysis to direct smears of metastatic melanoma

BACKGROUND: The cytodiagnosis of melanoma in fine‐needle aspiration (FNA) specimens can be challenging, often requiring the use of immunocytochemistry. As constitutively activating mutations in the BRAF oncogene are present in at least 40% of melanomas, the use of FNA material to interrogate the BRA...

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Published in:Cancer cytopathology 2012-02, Vol.120 (1), p.52-61
Main Authors: Hookim, Kim, Roh, Michael H., Willman, Joseph, Placido, Jeremiah, Weigelin, Helmut C., Fields, Kristina L., Pang, Judy, Betz, Bryan L., Knoepp, Stewart M.
Format: Article
Language:English
Subjects:
Biological and medical sciences
BRAF
Cytodiagnosis - methods
cytology
Dermatology
direct smear
DNA Mutational Analysis
HMB‐45
Humans
immunocytochemistry
Immunohistochemistry
Mart‐1
Medical sciences
melanoma
Melanoma - diagnosis
Melanoma - genetics
Melanoma - pathology
Melanoma - secondary
Mutation
Proto-Oncogene Proteins B-raf - genetics
S‐100
Tumors of the skin and soft tissue. Premalignant lesions
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Summary:BACKGROUND: The cytodiagnosis of melanoma in fine‐needle aspiration (FNA) specimens can be challenging, often requiring the use of immunocytochemistry. As constitutively activating mutations in the BRAF oncogene are present in at least 40% of melanomas, the use of FNA material to interrogate the BRAF mutational status is likely to increase. Because cell blocks, traditionally used for these studies, can occasionally exhibit insufficient tumor cellularity, the authors investigated the utility of direct smears for immunocytochemistry and BRAF mutational analysis. METHODS: Immunocytochemistry for S‐100, HMB‐45, and Mart‐1 was prospectively performed on direct smears in 17 FNAs of metastatic melanoma. Next, BRAF sequencing was performed using DNA isolated from archived Diff‐Quik–stained direct smears for 15 cases. In parallel, sequencing was performed using DNA obtained from corresponding cell blocks. RESULTS: S‐100 positivity in the tumor cells was observed in all 17 cases. HMB‐45 and Mart‐1 positivity was noted in 81% and 88% of cases, respectively. All 3 markers were positive in 76% of cases. Next, of the 15 archived melanoma FNAs tested, BRAF mutations were observed in 8 (53%); 5 and 3 melanomas harbored the V600E and V600K mutation, respectively. Corresponding cell blocks were also tested for all 15 cases, yielding concordant BRAF results in 14 (93%); 1 cell block yielded a false‐negative result. CONCLUSIONS: Cytologic direct smears represent a robust and valuable source of cellular material for immunocytochemistry and molecular studies, especially in instances in which inadequate cell block cellularity is anticipated or encountered. Cancer (Cancer Cytopathol) 2012. © 2011 American Cancer Society. This study demonstrates that direct smears represent a robust and valuable source of cellular material for ancillary studies used in the cytologic diagnosis of melanoma. Direct smears can be effectively used for confirmatory immunocytochemical studies and molecular assays designed to interrogate the BRAF mutational status of melanoma, especially in scenarios in which inadequate cell block cellularity is anticipated or encountered.
ISSN:1934-662X
1934-6638
DOI:10.1002/cncy.20180