CSTL · CIK 0001447362
What Castle Biosciences, Inc. told the SEC could break it.
Castle Biosciences' revenue is concentrated in a few payors, with reimbursement policy the dominant lever: Medicare was 44% of total revenue in 2025, so its diagnostic tests' fortunes hinge on Medicare Administrative Contractors, local coverage determinations, ADLT status and the PAMA-driven Clinical Laboratory Fee Schedule. Beyond Medicare, a single commercial payor accounted for about 16% of patient revenue, so a coverage cut there would also materially hurt results. On the supply side it depends on sole suppliers — ThermoFisher, Promega and Qiagen — for certain reagents, equipment and chips, some unique to those vendors, so despite alternate-sourcing efforts an interruption could disrupt testing.
3 self-disclosed vulnerabilities, pulled from its own filings, each in the company’s words, with the source. This is the risk register almost nobody reads.
In its own words
What could break it.
Regulatory & policy
- Medicare reimbursement (MAC/LCD/PAMA-CLFS)high
Medicare accounted for 44% of Castle Biosciences' total revenue in 2025; its diagnostic-test reimbursement depends on Medicare Administrative Contractors (Palmetto/Noridian, Novitas), local coverage determinations, ADLT status, and the PAMA-driven Clinical Laboratory Fee Schedule — so coverage or rate changes would materially affect revenue.
“We receive a substantial portion of our revenue from a small number of third-party payors. Our revenue from patients covered by Medicare as a percentage of total revenue, was 44% for the year ended December 31, 2025.”
Customer concentration
- single commercial payor (~16% of revenue)medium
Beyond Medicare, one commercial payor accounted for approximately 16% of Castle Biosciences' patient revenue in 2025 (unnamed); loss or coverage reduction by this payor would materially affect revenue.
“Additionally, there was a commercial payor from which 16% of our revenue from patients was derived for the year ended December 31, 2025.”
SEC filing →As of 2026
Sole-source dependency
- sole/unique-source diagnostic reagents, equipment and chipsmedium
Castle Biosciences procures certain reagents, equipment and chips/cards used to perform its tests from sole suppliers (ThermoFisher, Promega, Qiagen), some items being unique to those vendors; despite alternate-sourcing strategies, an inability to source could disrupt testing.
“We procure certain reagents, equipment, chips/cards and other materials used to perform our tests from sole suppliers such as ThermoFisher Scientific, Inc., Promega and Qiagen, Inc. Some of these items are unique to these suppliers and vendors.”
SEC filing →As of 2026
The hidden graph
Who it depends on, and who depends on it.
Relationships surfaced from filings, including ones disclosed by the other side, which is how the non-obvious ones come to light.
Its suppliers
“We procure certain reagents, equipment, chips/cards and other materials used to perform our tests from sole suppliers such as ThermoFisher Scientific, Inc., Promega and Qiagen, Inc. Some of these items are unique to these suppliers and vendors.”
Cited →Promega Corporation
“We procure certain reagents, equipment, chips/cards and other materials used to perform our tests from sole suppliers such as ThermoFisher Scientific, Inc., Promega and Qiagen, Inc. Some of these items are unique to these suppliers and vendors.”
Cited →Thermo Fisher Scientific, Inc.
“We procure certain reagents, equipment, chips/cards and other materials used to perform our tests from sole suppliers such as ThermoFisher Scientific, Inc., Promega and Qiagen, Inc. Some of these items are unique to these suppliers and vendors.”
Cited →
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