Here are 1-3 brief analogies for Castle Biosciences (CSTL):

• Exact Sciences for advanced skin cancer diagnostics.
• The Genomic Health for skin cancer.

• DecisionDx-Melanoma: This gene expression profile (GEP) test identifies a patient's individual risk of melanoma recurrence and metastasis.
• DecisionDx-SCC: This gene expression profile (GEP) test assesses a patient's risk of squamous cell carcinoma metastasis.
• MyPath Melanoma: This diagnostic test aids in differentiating benign nevi from melanoma.
• DecisionDx-UM (Uveal Melanoma): This gene expression profile (GEP) test assesses the metastatic risk of uveal melanoma.

Castle Biosciences (CSTL) provides genomic diagnostic tests, primarily for skin cancers. While these services are rendered to individual patients, the company's revenue largely comes from third-party payers who reimburse for these tests. As such, Castle Biosciences primarily sells its services to other companies in the form of major commercial health insurance providers, as well as to government programs like Medicare and Medicaid.

Castle Biosciences contracts with a broad range of these payers. Although the company does not typically disclose specific revenue concentration from individual insurers, the following are some of the largest commercial health insurance companies in the U.S. that serve as major payers for the types of diagnostic tests provided by Castle Biosciences:

• UnitedHealth Group (Symbol: UNH)
• Elevance Health (Symbol: ELV)
• CVS Health (which owns Aetna) (Symbol: CVS)

In addition to these commercial companies, government programs such as Medicare and Medicaid are also significant payers for Castle Biosciences' services, although they are not "companies" in the traditional sense.

• Thermo Fisher Scientific Inc. (TMO)
• Integrated DNA Technologies (subsidiary of Danaher Corporation, DHR)

Derek Maetzold, Founder, President and Chief Executive Officer

Derek J. Maetzold founded Castle Biosciences in September 2007 and has served as its President, Chief Executive Officer, and as a member of its board of directors since inception. Prior to founding Castle Biosciences, he held leadership roles at Encysive Pharmaceuticals, Schering-Plough Corporation (now Merck), Integrated Communications, Amylin Pharmaceuticals, and Sandoz Pharmaceuticals (now a division of Novartis). Mr. Maetzold successfully led Castle Biosciences through several rounds of private financing, a successful IPO in July 2019, and two acquisitions in 2021. He is a co-inventor of a number of technologies at Castle Biosciences and Encysive Pharmaceuticals.

Frank Stokes, Chief Financial Officer

Frank Stokes has served as Chief Financial Officer of Castle Biosciences since December 2017. Before joining Castle, he served as Chief Financial Officer for Hammock Pharmaceuticals. Mr. Stokes also held positions as a Managing Director at Leerink Swann (now SVB Leerink), Robert W. Baird & Co. Incorporated, and Wachovia Securities, LLC, where he led life sciences, tools, and diagnostics sector investment banking efforts and managed financings and mergers and acquisitions transactions. He was instrumental in Castle Biosciences' initial public offering in 2019 and the Company's acquisitions of Cernostics, Inc. in 2021 and AltheaDx, Inc. in 2022.

Kristen Oelschlager, Chief Operating Officer

Kristen Oelschlager has served as Chief Operating Officer of Castle Biosciences since April 2021. She joined the company as Executive Director of Operations in October 2008 as one of three initial employees. Her previous roles at Castle Biosciences include Chief Operations Officer (August 2020 to April 2021) and Senior Vice President, Clinical Operations (January 2018 to August 2020).

Toby Juvenal, Chief Commercial Officer

Toby Juvenal is a co-founder of Castle Biosciences, which commenced operations in late 2008. He currently holds the position of Chief Commercial Officer.

Matthew Goldberg, M.D., Senior Vice President, Medical

Dr. Matthew Goldberg has served as Senior Vice President, Medical, since May 2023. He joined Castle Biosciences in August 2020 as Medical Director. Prior to his time at Castle Biosciences, Dr. Goldberg was an Assistant Professor in Dermatology and Pathology at the Icahn School of Medicine at Mount Sinai in New York and maintains his affiliation as an Assistant Clinical Professor of Dermatology.

Castle Biosciences (CSTL) faces several key risks that could impact its business operations and financial performance. These risks primarily revolve around the company's ability to achieve profitability, navigate the complex healthcare reimbursement landscape, and manage regulatory challenges inherent in the diagnostics industry.

1. Challenges in Profitability and Operational Efficiency: Despite strong revenue growth, Castle Biosciences has demonstrated challenges in achieving profitability, evidenced by negative operating and net margins. The company reported a negative operating margin of -10.17% and a net margin of -3.56%. Additionally, a negative Earnings Per Share (EPS) of -0.44 and a return on equity of -2.70% indicate that the company is currently not generating profit from its equity base, posing significant financial hurdles.
2. Reimbursement Uncertainty and Intense Competitive Pressure: The company operates in a diagnostics market characterized by competitive pressures and lingering reimbursement uncertainty. These factors could potentially hinder the adoption of Castle Biosciences' tests, compress its margins, and challenge its projected growth expectations. Regulatory changes within the healthcare industry also contribute to these sector-specific risks.
3. Regulatory Changes and Potential FDA Disruptions: As a molecular diagnostics company, Castle Biosciences is highly susceptible to disruptions and changes originating from the U.S. Food and Drug Administration (FDA) and other government agencies. Issues such as layoffs, funding shortages, or broader global health concerns could impede the FDA's capacity to review clinical trials or approve new products. Such delays could adversely affect the company's operations and product pipeline. The unpredictability of government funding and political priorities further intensifies this risk.

Castle Biosciences (CSTL) focuses on diagnostic and prognostic tests for skin cancers and other conditions, with several key products addressing significant markets in the U.S.

• AdvanceAD-Tx: This test, designed to guide systemic treatment selection for patients with moderate to severe atopic dermatitis, has an estimated total addressable market opportunity of approximately $33 billion in the U.S. alone.
• TissueCypher Barrett's Esophagus: This spatial omics test, which predicts the future development of high-grade dysplasia and/or esophageal cancer in patients with Barrett's esophagus, adds an estimated $1 billion to the total U.S. addressable market.
• DecisionDx-Melanoma: This gene expression profile (GEP) test, which assesses the risk of metastasis for patients with cutaneous melanoma, has an estimated total addressable market of approximately $540 million in the U.S.
• MyPath Melanoma: Part of Castle Biosciences' diagnostic GEP offering for difficult-to-diagnose melanocytic lesions, the estimated U.S. total addressable market is approximately $600 million.
• DecisionDx-UM: This GEP test, which predicts the risk of metastasis for patients with uveal melanoma, has an estimated total addressable market of approximately $10 million in the U.S.
• DecisionDx-SCC: This GEP test predicts the risk of metastasis for patients with cutaneous squamous cell carcinoma (SCC) who have one or more risk factors. While a specific dollar amount for the addressable market was not found, the annual U.S. incidence for squamous cell carcinoma is estimated at 1,000,000, with the addressable market limited to carcinomas with one or more high-risk features.
• IDgenetix: This pharmacogenomic (PGx) test, which guided personalized mental health medication selection, had an estimated U.S. total addressable market of approximately $5 billion. However, the Company discontinued its IDgenetix test offering effective May 2025.

• Increased Adoption of Core Dermatologic Tests: The company anticipates continued strong adoption of its core dermatologic tests, DecisionDx®-Melanoma and DecisionDx®-SCC. Both tests have demonstrated significant year-over-year growth in test reports, with DecisionDx-Melanoma reports increasing by 12% year-over-year in Q3 2025 and DecisionDx-SCC showing a 49% increase in Q3 2024. This growth is further supported by expanded clinical evidence for their use, reinforcing their position as key revenue drivers.
• Growth of TissueCypher® Barrett's Esophagus Test: Castle Biosciences projects sustained growth from its TissueCypher® Barrett's Esophagus test, which achieved over 10,000 test reports in a single quarter for the first time in Q3 2025, marking a 75% year-over-year growth. This test is a significant contributor to the company's non-dermatologic revenue and is expected to continue its upward trajectory as a core revenue driver.
• Launch and Expansion of New Products, including AdvanceAD-Tx™: The recent launch of AdvanceAD-Tx™, a test designed to guide systemic treatment selection for patients with moderate-to-severe atopic dermatitis, represents a significant new product innovation. While its revenue impact is expected to be minimal in 2026, it opens a new market with high clinical need and offers future growth potential. Castle Biosciences also has active research and development programs for other tests in dermatology, gastroenterology, and other high-need diseases.
• Strategic Initiatives and Enhanced Market Penetration: The company's focus on strategic initiatives, disciplined capital allocation, and continuous evolution is expected to contribute to revenue growth. These efforts include ongoing investments in growth plans, such as the acquisition of Previse to expand the gastrointestinal portfolio, and improving market penetration through physician education and a maturing sales force.
• Improved Reimbursement Opportunities: Castle Biosciences is actively pursuing FDA approval for its tests, which is expected to enhance future reimbursement opportunities. Advances in reimbursement are anticipated to improve pricing and margins, thereby supporting revenue growth.

Share Issuance

• Castle Biosciences commenced a proposed underwritten public offering to issue and sell $125,000,000 of common stock in December 2020.
• The number of outstanding common shares increased from 27,449,983 as of February 21, 2024, to 29,008,281 as of July 28, 2025, indicating further share issuances, likely related to employee benefit plans.

Outbound Investments

• In the second quarter of 2025, Castle Biosciences closed the Previse tuck-in acquisition.
• During Q2 2025, the company also announced a collaboration and license agreement with SciBase.

Capital Expenditures

• Capital expenditures are increasing, with $14 million in capex during the first half of 2025, contributing to property and equipment growing to $74.1 million.
• The primary focus of capital expenditures is on automating and expanding laboratories to reduce per-test costs and handle increased volumes.
• The company utilizes financing activities to fund capital expenditures and business expansion campaigns.