What is the 13F Pro Quality Score for CSTL?

13F Pro ranks CASTLE BIOSCIENCES INC (CSTL) on the 13F Pro Quality Score, a 0–100 composite of 32 fundamental signals including return on invested capital, free cash flow consistency, balance-sheet strength, earnings quality, growth durability, and valuation discipline. The score refreshes after each 10-K and 10-Q filing on SEC EDGAR. View CSTL's current score at https://13fpro.ai/research/CSTL (free sign-up required for the full ranking).

Which hedge funds own the most CSTL stock?

Based on the most recent Form 13F-HR filings on SEC EDGAR, the largest reported institutional holders of CSTL include BlackRock,, RTW INVESTMENTS,, PRINCIPAL FINANCIAL GROUP. Holdings are reported quarterly within 45 days of quarter-end and updated on https://13fpro.ai/research/CSTL as soon as new 13F filings post.

Where does 13F Pro source CSTL data?

All CASTLE BIOSCIENCES INC fundamentals and ownership data come directly from SEC EDGAR. CASTLE BIOSCIENCES INC files with the SEC under CIK 1447362. 13F Pro ingests XBRL financial facts from 10-K and 10-Q filings, Form 13F-HR institutional holdings, and Form 4 insider transactions, with no third-party rewrites or estimates.

What sector is CSTL in?

CASTLE BIOSCIENCES INC (CSTL) is classified in the Healthcare sector. 13F Pro publishes sector-level fund flow analysis and quality leaders at https://13fpro.ai/research/sector/healthcare.

How often is CSTL research updated on 13F Pro?

CSTL's fundamentals refresh within hours of each new 10-K or 10-Q filing on SEC EDGAR. Institutional ownership updates after each quarterly 13F filing window. Insider transactions update after each Form 4 filing. The 13F Pro Quality Score recalculates after every fundamentals refresh.

CASTLE BIOSCIENCES INC(CSTL)Stock Analysis

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13F Pro Quality Score

37.7/100

Rank #2,042 of 2,879 stocks

View Healthcare peers →

Rankings refresh quarterly once 80% of peers have filed (~45 days after quarter-end). Next update: ~Aug 14, 2026.

Revenue Growth

93.4/100

Profitability

18.5/100

Balance Sheet

22.1/100

Earnings Quality

30.0/100

Free Cash Flow

20.9/100

Institutional Flow

39.5/100

Revenue Scale

31.5/100

Dilution Risk

13.7/100

CSTL Stock Analysis & AI Quality Score

AI stock analysis and institutional research for CASTLE BIOSCIENCES INC (CSTL), a Healthcare sector company. 13F Pro's AI-powered ranking engine scores CSTL at 37.7/100 on a 32-signal composite quality model, placing it at rank #2,042 of 2,879 stocks — the bottom half of the AI-ranked universe. CSTL scores in the top quartile across revenue growth (93.4). Areas of concern include profitability (18.5) and free cash flow (20.9), which score below median versus the broader universe. Shareholder dilution risk is elevated at 13.7/100, reflecting ongoing share issuance or stock-based compensation. Based on the latest XBRL financial filings (Q1 2026), CASTLE BIOSCIENCES INC reports quarterly revenue of $83.7M, net income of $-14.5M, free cash flow of $-34.6M. Top institutional holders of CSTL by reported 13-F value include BlackRock,, RTW INVESTMENTS,, PRINCIPAL FINANCIAL GROUP, based on the most recent SEC filings. CSTL trades on the Nasdaq exchange and files with the SEC under CIK 1447362. 13F Pro's AI research platform runs 10 specialized AI analysts — value, growth, momentum, macro, and activist specialists — that debate CSTL daily and publish AI-generated analysis with cited SEC sources. The platform aggregates historical XBRL financial facts, 10-Q and 10-K filings, insider Form 4 transactions, and institutional 13-F holdings for CASTLE BIOSCIENCES INC directly from SEC EDGAR. CASTLE BIOSCIENCES INC's 13F Pro composite quality score has ranged between 8 and 86 since 2021, currently 37.7 — a declining long-term trajectory across 56 quarterly and live scoring snapshots.

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Fun facts about CASTLE BIOSCIENCES INC

Quirks, history, and lore behind CSTL — the kind of stuff that makes a stock memorable.

1
The Basics
U.S. healthcare company · small-cap · listed on Nasdaq · headquartered in Texas.
2
The Numbers
Annual revenue in the range of roughly $100 million, serving a niche but growing corner of molecular diagnostics — tiny company, outsized clinical ambitions.
3
The History
Founded in the 2010s, it went public around 2019 and built its business around the idea that a single skin biopsy could tell you far more than a pathologist's eye alone.
4
The Secret
Its core products use gene expression profiling to help doctors decide how aggressively to treat melanoma and other skin cancers — sparing some patients from brutal therapies they don't need.
5
The Lore
It has expanded beyond skin cancer into uveal melanoma and Barrett's esophagus testing, turning a dermatology niche into a broader precision oncology platform.
6
The Giveaway
Its flagship test, DecisionDx-Melanoma, is practically synonymous with the company — a biosciences firm named after a fortified structure that's storming the genomic skin-cancer testing market.

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Revenue

Q1 2026

$83.7M

Net Income

Q1 2026

$-14.5M

Free Cash Flow

Q1 2026

$-34.6M

ROIC

Q1 2026

-3.9%

D/E Ratio

Q1 2026

0.03

Revenue & Net Income

Earnings Per Share

Key Financials Over Time

Export Financial Table · Pro+

Revenue

+3.7% YoY

$344.2MFY 2025

FY21 $94.1MFY22 $137.0MFY24 $332.1MFY25 $344.2M

Net Income

-232.4% YoY

$-24.2MFY 2025

FY21 $-31.3MFY22 $-67.1MFY24 $18.2MFY25 $-24.2M

Operating Income

-593.8% YoY

$-42.8MFY 2025

FY21 $-40.1MFY22 $-72.9MFY24 $8.7MFY25 $-42.8M

EPS (Diluted)

-233.9% YoY

$-0.83FY 2025

FY21 $-1.24FY22 $-2.58FY24 $0.62FY25 $-0.83

Total Assets

+8.9% YoY

$578.6MFY 2025

FY21 $462.6MFY22 $447.3MFY24 $531.2MFY25 $578.6M

Total Debt

+1.7% YoY

$10.5MFY 2025

FY21 —FY22 —FY24 $10.3MFY25 $10.5M

Op. Cash Flow

-0.8% YoY

$64.3MFY 2025

FY21 $-19.0MFY22 $-41.7MFY24 $64.9MFY25 $64.3M

Metric	FY 2025	FY 2024	FY 2022	FY 2021	FY 2020	FY 2018
Revenue	$344.2M +3.7%	$332.1M +142.3%	$137.0M +45.7%	$94.1M +50.2%	$62.6M +174.9%	$22.8M
Net Income	$-24.2M -232.4%	$18.2M +127.2%	$-67.1M -114.6%	$-31.3M -204.3%	$-10.3M -61.5%	$-6.4M
Operating Income	$-42.8M -593.8%	$8.7M +111.9%	$-72.9M -81.8%	$-40.1M -512.6%	$-6.5M -70.5%	$-3.8M
EPS (Diluted)	$-0.83 -233.9%	$0.62 +124.0%	$-2.58 -108.1%	$-1.24 -129.6%	$-0.54 +89.9%	$-5.33
Total Assets	$578.6M +8.9%	$531.2M +18.8%	$447.3M -3.3%	$462.6M +5.3%	$439.3M +1860.8%	$22.4M
Total Debt	$10.5M +1.7%	$10.3M	—	—	$0.00 -100.0%	$24.5M
Operating Cash Flow	$64.3M -0.8%	$64.9M +255.7%	$-41.7M -119.4%	$-19.0M -292.4%	$9.9M +180.2%	$-12.3M

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Available Research

13F Pro tracks comprehensive data for CASTLE BIOSCIENCES INC including:

SEC EDGAR filings (10-K, 10-Q, 8-K)

XBRL financial facts (revenue, EPS, margins)

Insider transactions (Form 4)

Institutional 13F holdings

Quality rankings (32 signals)

AI analyst debates & daily meetings

Historical financial trends

Peer comparison & sector analysis

Top Institutional Holders of CSTL

BlackRock, Inc.
$73.2M2,982,946 sh
RTW INVESTMENTS, LP
$67.7M2,758,335 sh
PRINCIPAL FINANCIAL GROUP INC
$43.5M1,769,877 sh
Portolan Capital Management, LLC
$33.1M1,350,283 sh
VANGUARD CAPITAL MANAGEMENT LLC
$28.9M1,177,522 sh
DIMENSIONAL FUND ADVISORS LP
$25.5M1,039,761 sh
SUMMIT PARTNERS PUBLIC ASSET MANAGEMENT, LLC
$23.1M940,685 sh
VANGUARD PORTFOLIO MANAGEMENT LLC
$21.2M861,771 sh
Allianz Asset Management GmbH
$19.9M811,324 sh
STATE STREET CORP
$18.9M769,079 sh

Fund	Value	Shares
BlackRock, Inc.	$73.2M	2,982,946
RTW INVESTMENTS, LP	$67.7M	2,758,335
PRINCIPAL FINANCIAL GROUP INC	$43.5M	1,769,877
Portolan Capital Management, LLC	$33.1M	1,350,283
VANGUARD CAPITAL MANAGEMENT LLC	$28.9M	1,177,522
DIMENSIONAL FUND ADVISORS LP	$25.5M	1,039,761
SUMMIT PARTNERS PUBLIC ASSET MANAGEMENT, LLC	$23.1M	940,685
VANGUARD PORTFOLIO MANAGEMENT LLC	$21.2M	861,771
Allianz Asset Management GmbH	$19.9M	811,324
STATE STREET CORP	$18.9M	769,079

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Is CSTL a good stock to buy?

13F Pro's AI-powered analysis of CASTLE BIOSCIENCES INC (CSTL) draws on SEC EDGAR-sourced fundamentals, institutional 13F holdings, and insider Form 4 transactions in the Healthcare sector (listed on Nasdaq). The 32-signal AI Quality Score, current rank, and full bull/bear verdict for CSTL are available on the CSTL stock profile dashboard — with the same data, AI insights, ratios, and institutional activity refreshed after every 10-K, 10-Q, 13F, and Form 4 filing.

Which hedge funds own CSTL?

Institutional investors are required to disclose their holdings quarterly via SEC Form 13F. 13F Pro aggregates these filings to show which hedge funds, mutual funds, and asset managers are buying or selling CSTL. Combined with insider transaction data from Form 4 filings and AI-powered analysis from 10 specialized research agents, 13F Pro provides a comprehensive view of CASTLE BIOSCIENCES INC's investment landscape.