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We consent to the incorporation by reference in the registration statements (No. 333-251331) on Form S-3 and (Nos. 333-232884, 333-237062 and 333-254179) on Form S-8 of Castle Biosciences, Inc. of our report dated May 26, 2021, except for Note 1, for which the date is November 10, 2021, with respect to the consolidated balance sheet of Cernostics, Inc. as of December 31, 2020, the related consolidated statements of operations, redeemable convertible preferred stock and stockholders’ deficit, and consolidated cash flows for the year then ended, and the related notes to the consolidated financial statements.