The First Report of BRAF V600E Mutation in Paratesticular Mesothelioma.
Ting Zhao, Yin P Hung, Adam S Fisch et al.
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Case in brief
A 44-year-old man with a history of asbestos exposure presented with painless right testicular swelling. Orchiectomy showed a 1.5-cm biphasic paratesticular mesothelioma, predominantly sarcomatoid (80%) with an epithelioid component (20%). The tumor expressed mesothelial markers, with BAP1, MTAP, and Merlin expression intact. Next-generation sequencing identified BRAF V600E, confirmed by immunohistochemistry. After adjuvant chemotherapy, he remained free of disease at 11 months of follow-up.
What made this case unusual
The tumor harbored BRAF V600E, a mutation described as exceptionally rare in mesothelioma; this was the first reported paratesticular mesothelioma with this alteration.
Diagnostic / clinical pearl
BRAF V600E can occur in paratesticular mesothelioma, including a biphasic tumor with intact BAP1, MTAP, and Merlin expression; molecular testing and confirmatory immunohistochemistry identified the alteration in this case.
Why it matters
The finding adds a molecular feature to the limited clinicopathologic characterization of paratesticular mesothelioma.