Castle Biosciences Balances Strong Growth With Margin Strain

Castle Biosciences ((CSTL)) has held its Q4 earnings call. Read on for the main highlights of the call.

Castle Biosciences’ latest earnings call painted a mixed but generally constructive picture, pairing robust test-volume growth and a strong balance sheet with sharply weaker profitability and mounting reimbursement and regulatory uncertainty. Management struck a confident tone on long-term adoption of its dermatology and gastroenterology franchises, even as near-term margin pressure and policy risks kept investor sentiment cautious.

Revenue Tops Expectations Despite Product Headwinds

Castle Biosciences reported Q4 2025 revenue of $87.0 million and full-year revenue of $344.2 million, both ahead of prior guidance and underscoring solid commercial execution. The beat came even as the company absorbed lost revenue from DecisionDx‑SCC, highlighting the resilience of its remaining portfolio and the growing contribution from newer assays.

Test Volumes Surge Across the Portfolio

Total test report volume reached 105,053 in 2025, up 37% from 2024, signaling strong demand despite reimbursement noise. For investors, this volume momentum matters because it underpins future revenue potential and suggests Castle is deepening its reach among dermatologists and gastroenterologists in core indications.

TissueCypher Emerges as a Key Growth Engine

TissueCypher stood out as a major growth driver, delivering 39,014 test reports in 2025 versus 20,956 in 2024, an 86% jump that pushed cumulative orders past roughly 80,000. New ordering clinicians climbed to 2,082 from 1,234, a near 69% increase, with patient penetration exiting 2025 at about 11%, leaving significant runway in the Barrett’s esophagus market.

DecisionDx-Melanoma Maintains Momentum and Depth of Evidence

DecisionDx‑Melanoma produced 39,083 test reports in 2025, a 9% year‑over‑year gain, with 1,795 clinicians ordering for the first time and lifetime ordering clinicians nearing 17,000. The test is supported by around 58 peer‑reviewed publications and reached roughly 31% patient penetration by year‑end, underscoring its entrenched position in melanoma risk stratification.

AdvanceAD-Tx Launch Shows Early Promise

The late‑November limited launch of AdvanceAD‑Tx into about 150 dermatology accounts generated encouraging early traction, with more than half of those accounts ordering within the first five weeks and roughly 500 orders by mid‑February. Management emphasized that revenue from this atopic dermatitis test will be immaterial in 2026, with more meaningful contributions expected from 2027–2028 as access and reimbursement develop.

M&A and Pipeline Investments Build Long-Term Optionality

Castle continued to deploy capital into innovation, acquiring Previse and its non‑endoscopic cell collection device, with a development study slated to begin enrollment in Q2 2026 and preliminary data targeted before year‑end. The company also advanced its collaboration with SciBase, planning an EIS PEN study in atopic dermatitis flares in Q2 2026, while reiterating that future deals must align with disciplined strategic and financial criteria.

Healthy Cash Pile and Positive Free Cash Flow

The balance sheet remains a key support for the investment case, with $299.5 million in cash, cash equivalents and marketable securities as of Dec. 31, 2025. Castle generated $28.3 million of free cash flow for the year, driven by $64.3 million in cash from operations against $36 million in capital expenditures, including $26.9 million of operating cash inflow in the fourth quarter alone.

Guidance Recasts Growth on a Core-Franchise Basis

For 2026, management guided to total revenue of $340 million to $350 million, which translates to mid‑ to high‑teens growth versus 2025 when excluding DecisionDx‑SCC and IDgenetix from both periods. The forecast assumes continued strength in DecisionDx‑Melanoma and TissueCypher, modest operating expense growth, lower capital spending than 2025, and minimal 2026 contribution from AdvanceAD‑Tx while reimbursement and coverage frameworks mature.

Profitability Under Pressure as Investments Ramp

Profitability deteriorated meaningfully in 2025, with a net loss of $24.2 million versus net income of $18.2 million in 2024, translating to a diluted loss per share of $0.83 against prior earnings of $0.62. Management framed the setback as the combined result of portfolio mix shifts, higher spending to support growth and pipeline development, and specific one‑time charges.

Adjusted EBITDA Slips on Margin Compression

Adjusted EBITDA fell to $11.5 million in Q4 2025 from $21.3 million a year earlier, and to $44 million for the full year compared with $75 million in 2024, a decline of roughly 41%. This drop underscores how higher operating costs and weaker gross margins are weighing on near‑term earnings power even as volumes climb.

Gross Margin Hit by Mix and One-Off Charges

GAAP gross margin contracted to 69.2% for 2025 from 78.5% in 2024, pressured by the loss of higher‑margin DecisionDx‑SCC revenue and a one‑time accelerated amortization charge of about $20.1 million. The margin reset raises the bar for future profitability, making sustained volume growth and operating leverage more important to restoring earnings traction.

Operating Expenses Continue Their Upward March

Total operating expenses, including cost of sales, rose 19.7% to $387 million in 2025 from $323.4 million in 2024, reflecting Castle’s decision to invest through the cycle. Sales and marketing spending climbed to $138.1 million from $123.5 million, while G&A increased to $91.2 million from $76.6 million, driven mainly by expanded headcount and higher compensation and IT costs.

Non-Operating and Stock-Based Costs Remain Meaningful

Interest income ticked down to $11.8 million in 2025 from $12.9 million in 2024, offering slightly less offset to operating losses despite the robust cash balance. Non‑cash stock‑based compensation remained substantial at $45.9 million, albeit improved from $50.3 million, and continues to be a factor for shareholders tracking dilution and underlying earnings quality.

Guideline and Reimbursement Risks Cloud Adoption

On the policy front, Castle flagged headwinds after an NCCN guideline update omitted a large portion of DecisionDx‑Melanoma’s evidence base, citing only 11 of 58 studies, while the MERLIN_001 study failed to meet a key threshold. The company also continues to feel the impact of prior coverage loss for DecisionDx‑SCC, creating uncertainty around guideline‑driven adoption and future margin recovery.

Limited Near-Term Payoff From New Launches

Despite positive early physician interest in AdvanceAD‑Tx, management expects revenue from the test to be immaterial in 2026 as it awaits clearer reimbursement signals, anticipated in the second half of the year. This timing gap underscores a broader commercialization risk where clinical uptake may outpace payment infrastructure, delaying revenue realization from innovation.

FDA Review Timeline Adds Another Layer of Uncertainty

Castle is preparing a de novo 510(k) submission for DecisionDx‑Melanoma, but the timeline to clearance remains uncertain, with management only suggesting a potential decision around late this year or early next year. Until that process is resolved, the company cannot fully unlock potential benefits from state biomarker laws and broader reimbursement improvements tied to formal regulatory status.

Guidance Points to Continued Growth With Measured Spending

Looking ahead, the company’s 2026 outlook implies steady core‑franchise expansion, anchored by growing melanoma and TissueCypher penetration, while operating expenses are expected to rise only moderately and capex trends lower from 2025’s $36 million. With no DecisionDx‑SCC revenue assumed and only minimal AdvanceAD‑Tx contribution this year, upside could emerge if reimbursement or regulatory milestones arrive earlier or stronger than anticipated.

Castle Biosciences’ earnings call framed a business in transition, trading near‑term profitability and margin strength for continued investment in growth platforms and pipeline assets. For investors, the story hinges on whether the company can convert its rising test volumes, deepening clinician adoption and sizable cash reserves into durable earnings once reimbursement, guideline and FDA uncertainties begin to clear.