Company Announcements

Data from 1,868 Surveillance, Epidemiology and End Results (SEER)-linked patients show DecisionDx-Melanoma significantly stratifies five-year melanoma-specific survival within American Joint Committee on Cancer (AJCC) stages and T categories, identifying patients whose mortality risk is substantially higher or lower than staging alone would predict

FRIENDSWOOD, Texas , March 27, 2026 /PRNewswire/ -- Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, will present new data at the 2026 American Academy of Dermatology (AAD) Annual Meeting, taking place March 27–31 in Denver, demonstrating that its DecisionDx-Melanoma test refines mortality risk within AJCC stages for patients with cutaneous melanoma (CM). The data show that DecisionDx-Melanoma identifies clinically meaningful differences in mortality risk among patients within the same stage, which may help clinicians more confidently escalate care for higher-risk patients while avoiding unnecessary interventions in those at lower risk of poor outcomes.

"The findings being presented at AAD reinforce that staging alone does not tell the whole story," said Harrison Nguyen M.D., MBA, MPH, lead study author and double board-certified dermatologist and fellowship-trained Mohs micrographic surgeon. "Incorporating DecisionDx-Melanoma into routine risk assessment provides physicians with biologic information that complements staging and supports more personalized management decisions, helping to identify patients who may warrant closer monitoring or earlier intervention, while also recognizing those who may be safely managed less intensively."

Detailed findings from this analysis will be presented in the following poster at AAD:

• ePoster: 76747 – The 31-GEP provides actionable risk stratification of 5-year melanoma specific survival rates within AJCC subgroups
• Lead Author: Harrison Nguyen M.D., MBA, MPH, Harrison Dermatology & Research Group, Missouri City, Texas

This poster from Castle's ongoing collaboration leveraging data from the National Cancer Institute's SEER Program registries evaluates risk stratification using the DecisionDx-Melanoma test in patients with CM across T categories and AJCC stages.

Traditional AJCC staging groups biologically distinct tumors based on clinicopathologic features alone, which can underestimate or overestimate a patient's true risk of poor outcomes. In this analysis, registry data from 22 SEER sites were linked to data from patients with stage I–III CM who were clinically tested with the DecisionDx-Melanoma test and had at least five years of follow up or death from their disease (n=1,868; 2013–2019). The test significantly stratified five-year melanoma-specific survival (MSS) within T categories and AJCC substages. In patients with T1 tumors, five-year MSS was 96.7% for those with low-risk (Class 1A) results versus 70.0% for high-risk (Class 2B) results, and among patients with Stage IIB–III disease, MSS was 87.4% for low-risk versus 48.5% for high-risk results (log-rank test; p<0.05).

Overall, the data show that DecisionDx-Melanoma can identify patients at higher or lower risk than predicted by AJCC staging alone, including high-risk T1 (thin) tumors with mortality risk approaching that of thicker melanomas, while also distinguishing lower-risk patients who may be appropriate for less intensive follow-up. These findings support integrating DecisionDx-Melanoma with staging to inform more precise, risk-aligned management decisions for patients with CM.

Full abstract content will be available in the AAD online viewing portal and onsite at the viewing stations beginning at the start of the meeting. They will also be published online via the Journal of the American Academy of Dermatology (JAAD) supplement in Fall 2026. For more information regarding Castle's posters and its participation at AAD, please visit booth #3345.

About DecisionDx-Melanoma
DecisionDx-Melanoma is a gene expression profile (GEP) test designed to analyze tumor biology to deliver a personalized risk assessment for patients with stage I–III cutaneous melanoma, enhancing risk stratification beyond American Joint Committee on Cancer (AJCC) staging alone. By combining molecular insights with select clinicopathologic features, the test provides two distinct outputs: a personalized risk of sentinel lymph node (SLN) positivity and a personalized risk of recurrence and/or metastasis. This clinically actionable information is designed to help guide risk-aligned patient management decisions, including SLN biopsy consideration, follow-up intensity, imaging and referrals.

DecisionDx-Melanoma is supported by more than 50 peer-reviewed publications, including prospective studies and meta-analyses, and was developed in collaboration with more than 100 leading U.S. institutions. The test has been clinically validated in more than 10,000 patient samples, ordered more than 220,000 times since launch, and has been shown to be associated with improved patient survival. Learn more at www.CastleBiosciences.com.

About Castle Biosciences
Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company improving health through innovative tests that guide patient care. With a primary focus in dermatologic and gastroenterological disease, we develop personalized, clinically actionable solutions that help improve disease management and patient outcomes.

We put people first—empowering patients and clinicians and informing care decisions through rigorous science and advanced molecular tests that support more confident treatment planning. To learn more, visit www.CastleBiosciences.com and connect with us on LinkedIn, Instagram, Facebook and X. 

DecisionDx-Melanoma, DecisionDx-CMSeq, i31-SLNB, i31-ROR, DecisionDx-SCC, MyPath Melanoma, AdvanceAD-Tx, TissueCypher, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are trademarks of Castle Biosciences, Inc.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are subject to the "safe harbor" created by those sections. These forward-looking statements include, but are not limited to, statements concerning: the ability of DecisionDx-Melanoma to (i) help clinicians more confidently escalate care for higher-risk patients while avoiding unnecessary interventions in those at lower risk of poor outcomes;(ii) identify patients at higher or lower risk than predicted by AJCC staging alone, including high-risk T1 (thin) tumors with mortality risk approaching that of thicker melanomas; and (iii) support more personalized management decisions by delivering a personalized risk assessment. The words "designed," "may", "can", and similar expressions are intended to identify forward intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements that we make. These forward looking statements involve risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements, including, without limitation: subsequent study or trial results and findings may contradict earlier study or trial results and findings or may not support the results obtained in these studies, including with respect to the discussion of our tests in this press release; actual application of our tests may not provide the aforementioned benefits to certain patients; and the risks set forth under the heading "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2025, and our subsequent Quarterly Reports on Form 10-Q, each as filed or to be filed with the SEC, and in our other filings with the SEC. The forward-looking statements are applicable only as of the date on which they are made, and we do not assume any obligation to update any forward-looking statements, except as may be required by law.

Investor Contact:
Camilla Zuckero
czuckero@castlebiosciences.com

Media Contact:
Allison Marshall
amarshall@castlebiosciences.com

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SOURCE Castle Biosciences, Inc.