cstl-20260730 0001447362 FALSE 0001447362 2026-07-30 2026-07-30 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 30, 2026 Castle Biosciences, Inc. (Exact name of registrant as specified in its charter) Delaware 001-38984 77-0701774 (state or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.) 1500 W. Parkwood Ave , Suite 400 Friendswood , Texas 77546 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: ( 866 ) 788-9007 (Former name or former address, if changed since last report.) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions: ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, $0.001 par value per share CSTL The Nasdaq Global Market Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b–2 of the Securities Exchange Act of 1934 (§ 240.12b–2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Item 2.02    Results of Operations and Financial Condition. On July 30, 2026, Castle Biosciences, Inc. (the “Company”) issued a press release announcing its financial results for the second quarter ended June 30, 2026. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information contained or incorporated in this Current Report on Form 8-K, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any filing under the Exchange Act or the Securities Act of 1933, as amended (the “Securities Act”), except as expressly set forth by specific reference in such filing to this Current Report on Form 8-K. Item 7.01    Regulation FD Disclosure. On July 30, 2026, the Company made available the slide presentation attached hereto as Exhibit 99.2. Information from this slide presentation may also be used by the management of the Company in future meetings regarding the Company. The information contained or incorporated in this Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.2, shall not be deemed “filed” for purposes of Section 18 of the Exchange Act or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any filing under the Exchange Act or the Securities Act except as expressly set forth by specific reference in such filing to this Current Report on Form 8-K. Item 9.01    Financial Statements and Exhibits. (d) Exhibits. Exhibit Number Description 99.1 Press release issued July 30 , 2026. 99.2 Slide presentation. 104 Inline XBRL for the cover page of this Current Report on Form 8-K. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has caused this report to be signed on its behalf by the undersigned hereunto duly authorized. CASTLE BIOSCIENCES, INC. By: /s/ Frank Stokes Frank Stokes Chief Financial Officer Date: July 30, 2026

Castle Biosciences announced Q2 2026 financial results on July 30, 2026, providing stakeholders with key performance metrics and operational insights for the quarter ended June 30, 2026.

On July 30, 2026, Castle Biosciences, Inc. announced its financial results for the second quarter ended June 30, 2026. The release highlighted key financial metrics and performance indicators that are critical for stakeholders. This announcement is significant as it not only reflects the company's operational efficiency over the second quarter but also informs investors of its strategic direction moving forward. The information can be found in the attached press release (Exhibit 99.1), though this Form 8-K filing clarifies that it should not be considered as 'filed' for regulatory purposes.

Castle Biosciences, Inc.

AI Executive Summary

Key Takeaways

Raw Filing Content

Filing Overview

What This Means