144 0001239501 XXXXXXXX LIVE 0001447362 Castle Biosciences, Inc. 001-38984 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 1-866-788-9007 Derek Maetzold Officer Common Goldman Sachs & Co. LLC 200 West Street New York NY 10282 14008 269513.92 30329952 05/07/2026 NASD Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 2714 10/29/2007 None Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 2306 10/29/2007 None Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 556 10/29/2007 None Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 556 10/29/2007 None Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 556 10/29/2007 None Common 10/29/2007 Acquired as gift Derek Maetzold Y 10/29/2007 556 10/29/2007 None Common 11/12/2018 Acquired as compensation -- Stock Options Issuer N 6764 11/12/2018 Compensation -- Cashless exercise / same-day sale N The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 116 3046.66 The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 116 3046.66 Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 662 17328.25 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 5408 140070.44 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 3587 93891.88 The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 199 5208.94 Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 498 13079.62 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 5676 147027.7 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 2639 69311.49 The Maetzold Descendants 2020 Trust dtd 12/4/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 621 16310.13 The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 83 2179.94 The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 163 4266.62 The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 166 4345.15 The Maetzold Descendants 2020 Trust dtd 12/4/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 736 19265.24 The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 113 2967.87 The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/11/2026 163 4266.62 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/12/2026 23179 584548.88 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/13/2026 13204 335209.95 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/16/2026 17575 455350.68 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/17/2026 18650 482441.93 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/18/2026 650 16461.71 The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 278 7086.55 The Maetzold Descendants 2020 Trust dtd 12/4/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 1357 34591.56 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 550 14020.16 The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 278 7086.55 The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 278 7086.55 Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 1153 29391.35 The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 03/26/2026 278 7086.55 The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 278 6941.34 The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 278 6941.34 The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 278 6941.34 Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 1153 28789.12 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 6214 155156.64 The Maetzold Descendants 2020 Trust dtd 12/4/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 1357 33882.78 The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/06/2026 278 6941.34 The Maetzold Descendants 2020 Trust dtd 12/4/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 1357 33975.31 The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 278 6960.3 Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 1153 28867.75 The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 278 6960.3 Derek Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 550 13770.39 The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 278 6960.3 The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold 1500 W. Parkwood Ave Suite 400 Friendswood TX 77546 Common 04/21/2026 278 6960.3 The sales of shares set forth herein are made in connection with a selling plan dated 12/3/2025 that is intended to comply with Rule 10b5-1(c). Total number of shares to be sold includes: 6,764 shares by Derek Maetzold, 2306 shares by DM 2020 Irrev Tr, 2714 shares by Maetzold Descendants 2020 Tr, 556 shares by Hannah Maetzold Irrev. Trust, 556 shares by Peter Maetzold Irrev. Trust, 556 shares by Emily Maetzold Irrev. Trust, 556 shares by John Maetzold Irrev. Trust. 05/07/2026 12/03/2025 Goldman Sachs & Co. LLC on behalf of Derek Maetzold