Castle Biosciences, Inc.
- Open
- 24.09
- Day high
- 24.34
- Day low
- 23.59
- Prev close
- 24.23
- Volume
- 239K
- Mkt cap
- $733M
- P/E (TTM)
- —
- EPS (TTM)
- —
- P/B
- 1.6
- P/S
- 2.2
- Yield
- —
- Per share
- —
- ▼Insiders net selling -$1.1M over the last 3 months (0 open-market buys, 35 sales)
- 🏛Institutions mixed (13F)
Castle Biosciences, Inc. (CSTL) is a Healthcare company listed on NASDAQ. The stock is up 46% over the past year. Over the trailing 3 months, insiders filed 0 open-market buys and 35 sales (SEC Form 4).
Castle Biosciences, Inc. (CSTL) financials & analyst ratings
Fundamentals (TTM)
Analyst consensus · 4 analysts
Source: exchange market data + company filings. Figures are trailing-twelve-month or as most recently reported. For informational purposes only — not investment advice.
CSTL earnings date, history & EPS estimates
| Report date | EPS est | EPS actual | Surprise | Revenue | Rev. surprise |
|---|---|---|---|---|---|
| May 6, 2026 | $-0.49 | $-0.49 | +0.0% | $84M | +6.3% |
| Feb 27, 2025 | $-0.04 | $0.32 | +900.0% | $86M | +2.9% |
| May 2, 2024 | $-0.37 | $-0.09 | +75.7% | $73M | +10.2% |
| Feb 28, 2024 | $-0.84 | $-0.10 | +88.1% | $66M | +17.5% |
| Nov 2, 2023 | $-0.92 | $-0.26 | +71.7% | $61M | +21.3% |
| Aug 2, 2023 | $-1.01 | $-0.70 | +30.7% | $50M | +13.5% |
| May 3, 2023 | $-0.80 | $-1.10 | -37.5% | $42M | -1.2% |
| Feb 28, 2023 | $-0.91 | $-0.78 | +14.3% | $38M | +3.3% |
| Nov 2, 2022 | $-0.70 | $-0.77 | -10.0% | $37M | +6.5% |
| Feb 28, 2022 | $-0.43 | $-0.25 | +41.9% | $25M | +5.5% |
| Mar 8, 2021 | $-0.11 | $-0.16 | -45.5% | $17M | — |
| Mar 10, 2020 | $-0.20 | $0.11 | +155.0% | $18M | -45.0% |
CSTL insider trading activity (SEC Form 4)
| Date | Insider | Type | Shares | Price |
|---|---|---|---|---|
| Jul 16, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 550 | $2.39 |
| Jul 16, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 278 | $22.92 |
| Jul 16, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,153 | $22.92 |
| Jul 16, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 550 | $22.92 |
| Jul 16, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,357 | $22.92 |
| Jul 6, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 400 | $24.78 |
| Jul 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 278 | $24.29 |
| Jul 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,357 | $24.29 |
| Jul 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 6,214 | $2.39 |
| Jul 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,153 | $24.29 |
| Jul 6, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 8,186 | $24.40 |
| Jul 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 6,214 | $24.29 |
| Jun 18, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 8,587 | $20.71 |
| Jun 17, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 550 | $2.39 |
| Jun 17, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,153 | $20.66 |
Source: CSTL SEC Form 4 filings, latest Jul 16, 2026. For informational purposes only — not investment advice.
See the full CSTL insider & 13F page →Castle Biosciences, Inc. company profile
Overview
Castle Biosciences, Inc. (NASDAQ:CSTL) is a commercial-stage diagnostics company founded in 2007 and headquartered in Friendswood, Texas. The company went public in July 2019 and has established itself as a leading provider of gene expression profile (GEP) tests for various medical conditions, with a primary focus on dermatological cancers. Castle has evolved from a single-product company focused on melanoma testing to a diversified diagnostics platform serving dermatology, gastroenterology, and mental health markets through both organic growth and strategic acquisitions.
Business
Castle Biosciences operates in the molecular diagnostics industry, which uses genetic testing to help physicians make treatment decisions for patients with various diseases. The company's core business revolves around gene expression profile (GEP) testing, a sophisticated form of genetic analysis that examines how genes are expressed in tumor tissue to predict disease progression and treatment outcomes. The company's flagship product is DecisionDx-Melanoma, a multi-gene expression profile test that analyzes tumor samples from patients diagnosed with invasive cutaneous melanoma to predict their risk of metastasis (cancer spreading to other parts of the body). Melanoma is the most dangerous form of skin cancer, and determining which patients are at high risk of metastasis helps doctors decide on appropriate treatment intensity and monitoring schedules. Castle's product portfolio spans three main business segments: 1. **Dermatology Franchise** (approximately 60-65% of revenue): This includes DecisionDx-Melanoma for melanoma risk assessment, DecisionDx-SCC for squamous cell carcinoma metastasis risk, and diagnostic tests like DecisionDx DiffDx-Melanoma and myPath Melanoma that help distinguish between benign and malignant skin lesions. 2. **Gastroenterology Franchise** (approximately 20-25% of revenue): Features TissueCypher, a test for patients with Barrett's esophagus (a precancerous condition) that predicts progression to esophageal cancer. This helps doctors determine which patients need more intensive surveillance. 3. **Mental Health Franchise** (approximately 10-15% of revenue): Includes IDgenetix, a pharmacogenomic test that analyzes how patients metabolize psychiatric medications, though the company announced discontinuation of this product line in 2025 due to challenging reimbursement conditions. The molecular diagnostics industry serves as a bridge between basic genetic research and clinical medicine, helping physicians move from a "one-size-fits-all" approach to personalized medicine based on individual patient biology.
Revenue model
Castle Biosciences generates revenue primarily through fee-for-service testing, where healthcare providers order tests for their patients and Castle performs the analysis in its laboratories. The company bills insurance companies, Medicare, or patients directly for each test performed, with pricing varying significantly based on the payer and reimbursement status. The company's revenue model depends heavily on reimbursement coverage from insurance providers. Tests with established reimbursement coverage, like DecisionDx-Melanoma, command higher prices (typically $3,000-$6,000 per test) and generate predictable revenue streams. Tests without coverage often require patients to pay out-of-pocket or are offered at reduced rates, significantly impacting margins. **Key Revenue Drivers and Margin Factors:** **Positive Margin Factors:** Established clinical evidence supporting test utility increases reimbursement likelihood and pricing power. Scale economies in laboratory operations reduce per-test costs as volumes grow. The company's proprietary technology and intellectual property provide pricing protection from competitors. **Negative Margin Factors:** Reimbursement denials or coverage losses can dramatically reduce test pricing and volumes, as seen with DecisionDx-SCC losing Medicare coverage in 2025. Increasing competition in molecular diagnostics puts pressure on pricing. Regulatory changes in healthcare reimbursement policies can impact coverage decisions. The business model is particularly sensitive to Medicare and commercial payer coverage decisions, as these determinations can shift a test from profitable to break-even or loss-making virtually overnight. The company invests heavily in clinical studies and health economics research to demonstrate test value and secure favorable coverage decisions. Customer acquisition occurs primarily through direct sales teams that educate physicians about test benefits and clinical utility. The company targets specialists like dermatologists, gastroenterologists, and psychiatrists who treat the relevant patient populations.
Competitive moat
Castle Biosciences possesses a moderate competitive moat built primarily on scientific expertise, clinical evidence, and regulatory advantages, though the strength varies significantly across its product portfolio. The company's strongest moat exists in its dermatology franchise, particularly DecisionDx-Melanoma, which benefits from **first-mover advantage** and extensive clinical validation. With over 200,000 tests performed and more than 50 peer-reviewed publications supporting its clinical utility, the test has achieved approximately 30% market penetration among eligible patients. This clinical evidence creates switching costs for physicians who have integrated the test into their practice patterns and builds trust with payers for reimbursement decisions. **Intellectual property** provides some protection, as Castle holds patents on its gene expression signatures and testing methodologies. The company's **regulatory expertise** in navigating complex reimbursement processes also creates barriers for potential competitors, as establishing coverage with Medicare and commercial payers requires substantial clinical evidence and can take years. However, the moat faces several **significant vulnerabilities**. The molecular diagnostics space is highly competitive, with large players like Exact Sciences and smaller specialized companies developing competing tests. **Reimbursement risk** represents the most critical threat, as coverage decisions can eliminate competitive advantages overnight, demonstrated by DecisionDx-SCC losing Medicare coverage despite strong clinical evidence. **Technology disruption** poses a long-term threat, as advances in artificial intelligence, liquid biopsies (blood-based tests), and other diagnostic modalities could make tissue-based gene expression testing obsolete. Additionally, **customer concentration risk** exists, as the company depends on relatively small numbers of specialist physicians in each therapeutic area. The company's newer products in gastroenterology and mental health have weaker moats due to less established clinical evidence and more challenging reimbursement environments. Overall, while Castle has built meaningful competitive advantages in its core dermatology business, the moat is not particularly wide and requires continuous investment in clinical evidence and market development to maintain.
Risks & safety
**Overall Assessment:** Castle Biosciences maintains a strong financial position with adequate liquidity and manageable debt levels, though profitability remains inconsistent and valuation appears elevated relative to current fundamentals. **Liquidity and Solvency:** - Strong cash position: $89.7 million in cash and short-term investments as of Q1 2025 - Excellent current ratio of 9.37, indicating strong short-term liquidity - Low debt-to-equity ratio of 0.059, minimal solvency risk - Recent negative free cash flow of -$10.8 million in Q1 2025, but positive $36.5 million for full year 2024 - Company guidance suggests positive cash flow for full year 2025 **Valuation Metrics:** - Trading at negative P/E ratio of -5.54 due to recent quarterly loss - Price-to-book ratio of 1.30, reasonable for a growth company - EV/EBITDA not meaningful due to inconsistent EBITDA generation - Graham Net-Net value of 9.07 suggests potential undervaluation from asset perspective **Other Considerations:** - Revenue growth remains strong at 21% year-over-year in Q1 2025 - Reimbursement headwinds create earnings volatility and uncertainty - Market cap of approximately $508 million appears reasonable given revenue run rate of ~$350 million annually - Business model scalability should improve margins as volumes grow, assuming stable reimbursement environment
Recent development
Castle Biosciences has undergone significant strategic evolution over the past few years, transforming from a single-product melanoma testing company into a diversified molecular diagnostics platform through both organic growth and strategic acquisitions. **Portfolio Diversification:** The company's most significant strategic pivot involved expanding beyond its core DecisionDx-Melanoma test through acquisitions. The 2021 acquisition of Cernostics brought TissueCypher for Barrett's esophagus testing, while the AltheaDx acquisition added IDgenetix pharmacogenomic testing for mental health. This diversification strategy aimed to reduce dependence on a single product and access new market opportunities. **Commercial Expansion:** Castle has substantially increased its sales force across all business lines, growing from a focused dermatology team to approximately 60-70 representatives covering dermatology, gastroenterology, and mental health markets. The TissueCypher team alone expanded to 65 representatives by 2025, reflecting the company's commitment to capturing market share in the gastroenterology space. **Pipeline Development:** The company has invested heavily in developing new tests, particularly an inflammatory skin disease test (likely for atopic dermatitis) that could launch by the end of 2025. This represents a potential $1.9 billion total addressable market expansion and demonstrates Castle's commitment to organic innovation alongside acquisitions. **Strategic Refocusing:** Recognizing the challenges in mental health reimbursement, Castle announced the discontinuation of IDgenetix in May 2025, choosing to focus resources on higher-return opportunities. Simultaneously, the company signed a definitive agreement to acquire Previse, a gastrointestinal health company with complementary methylation technology, signaling a strategic focus on areas with stronger reimbursement prospects. **Reimbursement Challenges and Responses:** The loss of Medicare coverage for DecisionDx-SCC in 2025 prompted Castle to explore multiple reconsideration pathways while continuing to offer the test based on clinical value. This demonstrates the company's commitment to long-term market position despite short-term reimbursement setbacks.
CSTL company profile · for informational purposes only — not investment advice.
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