Castle Biosciences (NASDAQ: CSTL) is a molecular diagnostics company that develops and commercializes proprietary gene expression profile tests to aid clinicians in diagnosing and treating cancers and precancerous conditions across dermatology, gastroenterology, and ophthalmology. Revenue comes from per-test fees billed primarily to third-party payors, including Medicare and commercial insurers. Medicare accounted for 44% of total revenue and a single commercial payor accounted for 16% of total revenue for the year ended December 31, 2025, reflecting material payer concentration. The commercial portfolio includes DecisionDx-Melanoma, DecisionDx-SCC, TissueCypher (Barrett's esophagus), DecisionDx-UM (uveal melanoma), MyPath Melanoma, and the newly launched AdvanceAD-Tx test for moderate-to-severe atopic dermatitis, which entered limited access launch in November 2025. Sales and marketing efforts focus on the U.S. dermatology and gastroenterology markets through a direct sales force. The company is headquartered in the United States and operates its own laboratory testing infrastructure, supported by approximately 158 peer-reviewed publications validating its test portfolio as of the FY2025 10-K filed February 26, 2026.

Revenue model

Per-test fee model billed to third-party payors. Medicare represented 44% of total revenue and one commercial payor represented 16% of total revenue for the year ended December 31, 2025. Revenue is transactional, tied to test report volume across the commercial portfolio.

Products and services

DecisionDx-Melanoma (risk stratification GEP test for cutaneous melanoma), DecisionDx-SCC (GEP test for high-risk cutaneous squamous cell carcinoma, estimated U.S. TAM $820 million), TissueCypher (risk stratification test for Barrett's esophagus), DecisionDx-UM (uveal melanoma), MyPath Melanoma (acquired with Myriad MyPath Laboratory in May 2021), AdvanceAD-Tx (487-gene GEP test for moderate-to-severe atopic dermatitis, limited launch November 2025, estimated U.S. TAM $33 billion). Esopredict methylation-based test acquired via Previse acquisition in May 2025, planned as supplemental offering beginning Q1 2026.

Customers and end markets

Clinicians in U.S. dermatology, gastroenterology, and ophthalmology. Reimbursement paid by Medicare (44% of FY2025 revenue) and commercial payors (one payor at 16% of FY2025 revenue). End patients include those with cutaneous melanoma, squamous cell carcinoma, Barrett's esophagus, uveal melanoma, and moderate-to-severe atopic dermatitis.

Value-chain role

Molecular diagnostic test developer and laboratory service provider. Receives tissue samples from third-party collectors, processes tests in its own laboratory, and delivers test reports to ordering clinicians. Develops proprietary algorithms and GEP assays internally.

Geographic exposure

Primarily United States. Sales and marketing focused on U.S. dermatology and gastroenterology markets as of FY2025 10-K.

Source: SEC 10-K, filed 2026-02-26

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