Castle Biosciences, Inc. (CSTL) Stock Analysis
Healthcare · Diagnostics & Research · NasdaqGM
Castle Biosciences, Inc. (CSTL) posted $344.23M in revenue for fiscal 2025 (up 3.7% year over year), with a net loss of $24.16M, and has compounded revenue about 40.6%/yr over five years, per its SEC filings.
Data last refreshed September 4, 2026 from SEC filings · how we compute this
The analyst's take on Castle Biosciences, Inc.
Castle Biosciences, Inc. has grown revenue from $22.79M to $344.23M over the last 8 fiscal years, compounding about 40.6% a year. The most recent year was up 3.7%, so growth has cooled from its longer-run pace.
Net margin sits at -7%, down 12.5 points year over year on a 79.4% gross margin. It carries about $10.06M of total debt.
At today's valuation the market is pricing in roughly 9.3% annual free-cash-flow growth — versus the 40.8% it actually delivered over the last five years, so the price is arguably undemanding against what it has already proven. It clears 3 of 7 deterministic health checks. The one thing worth a second look in the filings is inventory building faster than sales.
Synthesised from Castle Biosciences, Inc.'s SEC filings — descriptive, not advice. Ask the analyst your own question →
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Castle Biosciences, Inc. revenue & earnings — last 8 fiscal years
| Metric | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|---|---|
| Revenue | $22.79M | $51.87M | $62.65M | $94.08M | $137.04M | $219.79M | $332.07M | $344.23M |
| Gross profit | $17.49M | $44.55M | $52.96M | $78.26M | $105.03M | $174.81M | $271.86M | $273.20M |
| Net income | $-6.37M | $5.28M | $-10.28M | $-31.29M | $-67.14M | $-57.47M | $18.25M | $-24.16M |
| Net margin | -27.9% | 10.2% | -16.4% | -33.3% | -49.0% | -26.1% | 5.5% | -7.0% |
Source: Castle Biosciences, Inc. SEC filings (10-K).
Castle Biosciences, Inc. financial health: 3 of 7 checks passed
- ✓Revenue CAGR over 7 yrs (47.4%/yr)
- ✗Profitable every year (last 5)
- ✗Net margin above 10% (-7.0%)
- ✓More cash than total debt (cash 299.5M vs debt 10.5M)
- ✗Positive operating cash flow (last 5 yrs)
- ✓Free cash flow positive (latest yr) (28.3M)
- ✗Share count falling over 5 yrs (buybacks) (24.8M → 29.7M shares)
Checks computed deterministically from filed annual statements — no AI judgement.
Castle Biosciences, Inc.: 3 potential red flags in the filings
Patterns in the filed statements worth a second look — computed and cited, not AI guesswork, and not a signal to sell. The kind of thing that hides in a 10-K.
- Inventory building faster than salesInventory rose 26.0% versus revenue 3.7% — possible overproduction or softening demand.
- Share count rising (dilution)Shares outstanding grew 17.0% over 4 years (25.4M → 29.7M) — existing holders' stakes are being diluted.
- Currently unprofitableThe latest fiscal year was a net loss (net margin -7.0%).
What growth is priced into CSTL stock?
At today's market cap of $635.41M, Castle Biosciences, Inc. is priced for free-cash-flow growth of about 9.3% per year for 10 years (assuming a 10% discount rate and 2.5% terminal growth, base FCF $28.33M from the FY ending 2025-12-31). For comparison, free cash flow actually grew 40.8%/yr over the last five fiscal years and revenue 40.6%/yr, computed from its SEC filings. This is a reverse DCF — a translation of the price into a growth assumption you can judge, not a fair value and not advice. Change the assumptions yourself in the interactive view →
Explore 8 years of Castle Biosciences, Inc. financials — interactive
Full income statement, balance sheet and cash flow with CAGR and trend on every row, 48 quarters, valuation ratios, plain-English health checks, and Ask — our SEC-grounded research assistant.
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Castle Biosciences, Inc. financial history
About Castle Biosciences, Inc.
Castle Biosciences, Inc., a molecular diagnostics company, provides test solutions for the diagnosis and treatment of dermatologic cancers, Barrett's esophagus (BE), atopic dermatitis (AD), and uveal melanoma. The company offers DecisionDx-Melanoma, a risk stratification gene expression profile (GEP) test that predicts the likelihood of a positive sentinel lymph node and the risk of metastasis for patients with invasive cutaneous melanoma; TissueCypher, a risk stratification spatialomics test to predict future development of high-grade dysplasia and/or esophageal cancer in patients with non-dysplastic, indefinite dysplasia, and low-grade dysplasia BE; AdvanceAD-Tx, a non-invasive GEP test which is designed to guide systemic treatment selection for patients aged 12 years and older with moderateto-severe AD; DecisionDx-SCC, a GEP test for cutaneous squamous cell carcinoma; and MyPath Melanoma, a diagnostic GEP test for use in patients with difficult-to-diagnose melanocytic lesions. It also provides DecisionDx-UM, a risk stratification GEP test that predicts the risk of metastasis for patients with uveal melanoma. The company offers its products to dermatology and gastroenterology markets. The company was incorporated in 2007 and is headquartered in Friendswood, Texas.
Castle Biosciences, Inc. — frequently asked questions
What is Castle Biosciences, Inc.'s revenue?
Castle Biosciences, Inc. (CSTL) reported revenue of $344.23M for fiscal year 2025, up 3.7% from the prior year, according to its SEC filings.
Is Castle Biosciences, Inc. profitable?
No — CSTL reported a net loss of $-24.16M in fiscal 2025.
How fast is Castle Biosciences, Inc. growing?
CSTL's revenue grew at roughly 40.6% per year over the last five fiscal years (compound annual growth rate), computed from SEC-filed statements.
How much debt does Castle Biosciences, Inc. have?
As of fiscal year 2025, CSTL carried roughly $10.06M in total debt (short- plus long-term borrowings), per its filed balance sheet.
What is Castle Biosciences, Inc.'s gross margin?
CSTL's gross margin was 79.4% in fiscal 2025 — gross profit of $273.20M on revenue of $344.23M.
What is Castle Biosciences, Inc.'s market cap?
Castle Biosciences, Inc. (CSTL) has a market capitalization of about $635.41M, based on the latest data in our nightly-refreshed cache.
When does Castle Biosciences, Inc.'s fiscal year end?
CSTL's fiscal year ends in December. Its most recent annual filing covers the fiscal year ending 2025-12-31.
What growth is priced into CSTL stock?
At today's market cap of $635.41M, Castle Biosciences, Inc. is priced for free-cash-flow growth of about 9.3% per year for 10 years (assuming a 10% discount rate and 2.5% terminal growth, base FCF $28.33M from the FY ending 2025-12-31). For comparison, free cash flow actually grew 40.8%/yr over the last five fiscal years and revenue 40.6%/yr, computed from its SEC filings.
Where does this data come from?
All figures are computed from Castle Biosciences, Inc.'s official SEC filings (10-K and 10-Q), covering 8 years of history, refreshed nightly. stockportfolio.pro does not provide investment advice.