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Portolan Capital Management’s Castle Biosciences CSTL Stock Holding History

Portolan Capital Management’s Portfolio CSTL Stock Details CSTL Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$33.1M Sell
1,350,283
-379,180
-22% -$12.4M 1.76% 15
2025
Q4 		$67.3M Buy
1,729,463
+214,352
+14% +$6.91M 3.6% 3
2025
Q3 		$34.5M Buy
1,515,111
+25,539
+2% +$519K 1.87% 15
2025
Q2 		$30.4M Buy
1,489,572
+224,349
+18% +$4.15M 1.91% 12
2025
Q1 		$25.3M Buy
1,265,223
+488,644
+63% +$12.1M 1.93% 11
2024
Q4 		$20.7M Sell
776,579
-479,049
-38% -$14.6M 1.39% 20
2024
Q3 		$35.8M Buy
1,255,628
+44,676
+4% +$1.14M 2.6% 6
2024
Q2 		$26.4M Buy
1,210,952
+167,542
+16% +$3.73M 2.17% 10
2024
Q1 		$23.1M Buy
1,043,410
+314,757
+43% +$6.85M 1.76% 14
2023
Q4 		$15.7M Buy
728,653
+475,625
+188% +$8.37M 1.37% 17
2023
Q3 		$4.27M Sell
253,028
-178,446
-41% -$3.12M 0.4% 77
2023
Q2 		$5.92M Buy
431,474
+174,825
+68% +$3.54M 0.52% 58
2023
Q1 		$5.83M Sell
256,649
-327,067
-56% -$7.99M 0.56% 63
2022
Q4 		$13.7M Buy
583,716
+283,126
+94% +$6.56M 1.36% 24
2022
Q3 		$7.84M Buy
300,590
+145,622
+94% +$4.08M 0.83% 41
2022
Q2 		$3.4M Buy
+154,968
New +$3.6M 0.34% 93
2021
Q3 		– Sell
-9,127
Closed -$669K – 136
2021
Q2 		$669K Buy
+9,127
New +$603K 0.05% 125
2021
Q1 		– Sell
-16,573
Closed -$1.11M – 162
2020
Q4 		$1.11M Sell
16,573
-11,059
-40% -$599K 0.1% 133
2020
Q3 		$1.42M Sell
27,632
-44,202
-62% -$1.97M 0.16% 125
2020
Q2 		$2.71M Sell
71,834
-63,820
-47% -$2.18M 0.31% 101
2020
Q1 		$4.04M Sell
135,654
-169,924
-56% -$5.13M 0.61% 53
2019
Q4 		$10.5M Buy
305,578
+180,647
+145% +$4.42M 1.06% 37
2019
Q3 		$2.26M Buy
+124,931
New +$2.77M 0.25% 77

Other funds holding CSTL

BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
RI
RTW Investments New York $10B AUM 135.35% 1-Year Est. Return
Principal Financial Group
Principal Financial Group Des Moines, Iowa $187B AUM 18.48% 1-Year Est. Return
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
Dimensional Fund Advisors
Dimensional Fund Advisors Austin, Texas $481B AUM 30.42% 1-Year Est. Return
SPPAM
Summit Partners Public Asset Management Boston, Massachusetts $3.72B AUM 162.29% 1-Year Est. Return
VPM
Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM
Allianz Asset Management
Allianz Asset Management Munich, Germany $95.4B AUM 38.74% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $2.9T AUM 29.55% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return

Portolan Capital Management's CSTL Position: Q1 2026 in Review

Portolan Capital Management reduced its Castle Biosciences (CSTL) stake by 22% in Q1 2026, selling an estimated $12.4M and leaving 1,350,283 shares worth $33.1M. The position accounts for 1.76% of the portfolio, ranked #15.

Portolan Capital Management first reported a position in CSTL in Q3 2019 and has held it in 23 quarters since. The position peaked at $67.3M in Q4 2025. 186 funds tracked by Wall St. Rank hold CSTL as of Q1 2026.

  • Portolan Capital Management held 1,350,283 shares of Castle Biosciences worth $33.1M as of Q1 2026.
  • Portolan Capital Management sold 379,180 Castle Biosciences shares in Q1 2026, an estimated $12.4M.
  • Castle Biosciences made up 1.76% of Portolan Capital Management's portfolio in Q1 2026, its #15 holding.
  • Portolan Capital Management first reported a position in Castle Biosciences in Q3 2019 and has held it in 23 quarters since.
  • Portolan Capital Management's Castle Biosciences position peaked at $67.3M in Q4 2025.
  • 186 funds tracked by Wall St. Rank held Castle Biosciences as of Q1 2026.

Based on Portolan Capital Management's 13F filing for Q1 2026, filed 15 May 2026.