Castle Biosciences Inc. Common Stock (CSTL)

FairStock Score: 39/100 — MIXED

Key Financials

AI Analysis

AI-generated, general educational analysis — not personal investment advice.

I approach Castle Biosciences as a small molecular diagnostics business, where the product matters but the numbers must eventually cooperate. The top line is moving: in the quarter ended 2026-06-30, revenue was $103.5 million, up from $86.2 million in the quarter ended 2025-06-30. Yet the bottom line remains unreliable. For fiscal 2025, ended 2025-12-31, revenue was $344.2 million and net income was -$24.2 million, or -$0.83 per diluted share. That came after fiscal 2024, ended 2024-12-31, when revenue was $332.1 million and net income was $18.2 million, or $0.62 per diluted share. So revenue has grown, but profits have swung sharply. The most recent quarter, ended 2026-06-30, still showed a net loss of $2.1 million, though it narrowed from the fiscal Q1 2026 loss of $14.5 million in the quarter ended 2026-03-31. The balance sheet is conservative: debt-to-equity of 0.08 and FairStock's Altman Z-Score of 6.79 suggest low financial distress. But trailing free cash flow is about -$489,000, and ROE is -4.20% on a FairStock calculation. At the close on 2026-10-13, the price was $32.88, market cap $1.0 billion, P/B 2.13, and the P/E is negative because the company is loss-making; fiscal 2025 diluted EPS was -$0.83 in the year ended 2025-12-31. FairStock Score is 39/100. The Lynch category is TURNAROUND—loss in the latest year after earlier profits. I cannot confirm a durable competitive advantage from these figures alone; diagnostics can be reimbursement-sensitive and competitive. Until earnings and cash flow are consistently positive, the stock looks more speculative than clearly undervalued.

In plain English: Castle Biosciences sells lab tests that help doctors make treatment decisions for certain cancers and skin conditions. Sales are growing, but the company lost money in its latest full year and in the most recent quarter, so profits have been uneven. At the latest close, the price does not look clearly cheap compared with those weak current profits.

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Data as of 2026-10-13 close · note generated 2026-10-15 · model deepseek-flash

Sources (SEC EDGAR): fiscal Q2 2026 10-Q (period ended 2026-06-30) · fiscal Q1 2026 10-Q (period ended 2026-03-31) · fiscal Q3 2025 10-Q (period ended 2025-09-30) · fiscal Q2 2025 10-Q (period ended 2025-06-30) · FY2025 10-K (period ended 2025-12-31) · FY2024 10-K (period ended 2024-12-31) · FY2023 10-K (period ended 2023-12-31)

Fundamentals from company filings and market-data providers; prices are end-of-day, not real-time. AI-generated analysis is general and educational — not personal investment advice. Scoring methodology · Score test · Disclaimer