Director at Castle Biosciences (CSTL) settles 13,667 RSUs into common stock

Rhea-AI Filing Summary

CASTLE BIOSCIENCES director Tiffany Olson exercised previously granted equity awards rather than trading shares on the market. On May 22, 2026, she converted 13,667 Restricted Stock Units (RSUs) into the same number of Common Stock shares at a price of $0.00 per share, reflecting compensation rather than a cash investment.

Following this RSU settlement, Olson directly holds 39,573 shares of Castle Biosciences Common Stock. The filing shows no open-market purchases or sales and no shares withheld for taxes, indicating a straightforward vesting and settlement of RSUs, each of which represents the right to receive one share of Common Stock.

Insider Trade Summary

13,667 shares exercised/converted

Mixed 2 txns

Insider Olson Tiffany

Role null

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	13,667	$0.00	--
Exercise	Common Stock	13,667	$0.00	--

Holdings After Transaction: Restricted Stock Units — 0 shares (Direct, null); Common Stock — 39,573 shares (Direct, null)

Footnotes (1)

1. Each Restricted Stock Unit ("RSU") represents the right to receive one share of the Issuer's Common Stock. The RSUs vest in full on the earlier of the (a) one-year anniversary of the date on May 22, 2026, or (b) the day immediately preceding the next Annual Meeting of Stockholders following the date of the grant.

Key Figures

RSUs exercised: 13,667 shares Post-transaction holdings: 39,573 shares Exercise price per share: $0.00/share +1 more

4 metrics

RSUs exercised 13,667 shares Restricted Stock Units converted to Common Stock on May 22, 2026

Post-transaction holdings 39,573 shares Common Stock directly owned after RSU settlement

Exercise price per share $0.00/share RSUs settled into Common Stock without cash payment

Derivative RSU position after transaction 0 units Restricted Stock Units from this grant remaining after exercise

Key Terms

Restricted Stock Units, derivative security, Common Stock

3 terms

Restricted Stock Units financial

"Each Restricted Stock Unit ("RSU") represents the right to receive one share"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

derivative security financial

"transaction code description: Exercise or conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

Common Stock financial

"Each Restricted Stock Unit ("RSU") represents the right to receive one share of the Issuer's Common Stock"

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Olson Tiffany

(Last) (First) (Middle)

C/O CASTLE BIOSCIENCES, INC.

1500 W. PARKWOOD AVE SUITE 400

(Street)

FRIENDSWOOD TEXAS 77546

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
CASTLE BIOSCIENCES INC [ CSTL ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/22/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/22/2026		M		13,667	A	(1)	39,573	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Units	(1)	05/22/2026		M			13,667	(2)	(2)	Common Stock	13,667	$0	0	D

Explanation of Responses:

1. Each Restricted Stock Unit ("RSU") represents the right to receive one share of the Issuer's Common Stock.

2. The RSUs vest in full on the earlier of the (a) one-year anniversary of the date on May 22, 2026, or (b) the day immediately preceding the next Annual Meeting of Stockholders following the date of the grant.

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	05/27/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What did Castle Biosciences (CSTL) director Tiffany Olson report in this Form 4?

Director Tiffany Olson reported the settlement of equity awards, not an open-market trade. She exercised 13,667 Restricted Stock Units into 13,667 shares of Common Stock at $0.00 per share, reflecting compensation-based share delivery rather than buying or selling in the market.

How many Castle Biosciences (CSTL) shares did Tiffany Olson acquire and what are her holdings now?

Tiffany Olson acquired 13,667 shares of Castle Biosciences Common Stock through RSU settlement. After this transaction, she directly holds 39,573 shares. The change results from converting Restricted Stock Units into common shares, with no accompanying sale or tax-withholding disposition reported.

Was Tiffany Olson’s Castle Biosciences (CSTL) Form 4 a market purchase or sale of stock?

The Form 4 does not show a market purchase or sale. Instead, it records the exercise of 13,667 Restricted Stock Units into Common Stock at $0.00 per share, a compensation-related event where previously granted RSUs converted into shares without a cash transaction on an exchange.

What are Restricted Stock Units (RSUs) in the context of Castle Biosciences (CSTL)?

Restricted Stock Units are equity awards that convert into shares once vesting conditions are met. The filing notes each RSU represents the right to receive one share of Castle Biosciences Common Stock, meaning vesting and settlement increase share ownership without a market purchase.

Did Tiffany Olson retain any derivative positions after this Castle Biosciences (CSTL) RSU exercise?

The data provided shows no remaining derivative positions tied to this RSU grant after settlement. The RSU position for 13,667 units moved to zero, while her direct Common Stock holdings increased to 39,573 shares, indicating these particular RSUs were fully settled into stock.