Castle Biosciences' shares fell 19.9% post-earnings, driven by investor disappointment likely tied to cautious 2026 revenue guidance given strong reported test volume growth, suggesting market skepticism about sustainability or margin pressures.

• Q1 revenue reached $83.7 million, supported by 36% year-over-year growth in core test report volumes.
• DecisionDx-Melanoma test reports grew 16% year-over-year, with March hitting a record month.
• TissueCypher volumes surged 58% year-over-year, also achieving an all-time monthly high in March.
• The company raised 2026 revenue guidance to $345-$355 million, a modest increase from prior guidance, reflecting cautious outlook despite strong volume gains.
• New clinical data published and presented reinforce product differentiation but have not translated into more aggressive growth assumptions.