Castle Biosciences, Inc.
Castle Biosciences, Inc. (CSTL) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · CSTL · as of Mar 31, 2025
Ownership Breakdown
182
Institutional Holders
▼ 25 vs Q4
$516.29M
Total Inst. Value
▼ $190.12M vs Q4
30.33M
Shares Outstanding
freeFloat 88.25%
25.87M
13F Shares Held
▼ 635,412 vs Q4
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
CSTL largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
BLACKROCK, INC. services-medical laboratories | 2.98M | 10.43% | 10.43% | $59.73B | May 2, 2025 | ▲ 62.2K |
VANGUARD GROUP INC services-medical laboratories | 2.05M | 7.16% | 7.16% | $40.99B | May 9, 2025 | ▲ 215.0K |
PRINCIPAL FINANCIAL GROUP INC services-medical laboratories | 1.47M | 5.13% | 5.13% | $29.39B | Apr 28, 2025 | ▲ 32.2K |
PORTOLAN CAPITAL MANAGEMENT, LLC services-medical laboratories | 1.27M | 4.42% | 4.42% | $25.33B | May 15, 2025 | ▲ 488.6K |
DIMENSIONAL FUND ADVISORS LP services-medical laboratories | 1.20M | 4.20% | 4.20% | $24.03B | May 13, 2025 | ▲ 200.8K |
WASATCH ADVISORS LP services-medical laboratories | 998.5K | 3.49% | 3.49% | $19.99B | May 15, 2025 | ▼ 797.6K |
WELLINGTON MANAGEMENT GROUP LLP services-medical laboratories | 828.5K | 2.90% | 2.90% | $16.59B | May 13, 2025 | ▲ 106.4K |
STATE STREET CORP services-medical laboratories | 715.0K | 2.50% | 2.50% | $14.31B | May 15, 2025 | ▲ 4.8K |
RENAISSANCE TECHNOLOGIES LLC services-medical laboratories | 701.2K | 2.45% | 2.45% | $14.04B | May 14, 2025 | ▲ 16.2K |
ACADIAN ASSET MANAGEMENT LLC services-medical laboratories | 676.1K | 2.36% | 2.36% | $13.53B | May 21, 2025 | ▲ 267.4K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
30
Increased
+3.22M shares3
New Positions
first time holders16
Decreased
−2.98M shares0
Sold Out
fully exitedNet shares change (top 50)
+233.5K
+3.22M / −2.98M
Net new holders
+17
3 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
CSTL insider trading · insider activity
Source: SEC Form 4
5
Buy transactions
29
Sell transactions
0.17
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Olson Tiffany director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Goldberg Ellen director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Harrison Miles director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Cotton Rodney director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Caple Kim director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
BRADBURY DANIEL director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Cole G Bradley director | May 28, 2026 | Award | 11,766 | — | — | 11.8K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Castle Biosciences, Inc. (CSTL) is primarily owned by institutional investors, who hold approximately 85.3% of total shares outstanding. Company insiders own approximately 11.75%, while retail and public investors account for the remaining 2.95%.
The largest institutional shareholder of Castle Biosciences, Inc. is BLACKROCK, INC., holding approximately 2.98 million shares — equal to 10.43% of outstanding shares — as of March 31, 2025.
A total of 182 institutional investors currently hold CSTL stock, with a combined institutional value of approximately $516,286,662 as of the most recent 13F filing period.
Frequently asked questions
CSTL ownershipCastle Biosciences, Inc. (CSTL) is primarily owned by institutional investors, who hold approximately 85.3% of shares. The largest shareholder is BLACKROCK, INC. with a 10.43% stake. Company insiders hold 11.75%. Data sourced from SEC Form 13F as of March 31, 2025.