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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
Q2 		$7.84M Sell
328,818
-1,021,465
-76% -$22.8M 0.29% 95
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 $6.73T AUM 46.02% 1-Year Est. Return
RI
RTW Investments New York $11.7B AUM 174.13% 1-Year Est. Return
Principal Financial Group
Principal Financial Group Des Moines, Iowa $204B AUM 27.99% 1-Year Est. Return
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Acadian Asset Management
Acadian Asset Management Boston, Massachusetts $84.2B AUM 55.88% 1-Year Est. Return
Allianz Asset Management
Allianz Asset Management Munich, Germany $123B AUM 45.23% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
SPPAM
Summit Partners Public Asset Management Boston, Massachusetts $5.69B AUM 259.25% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $3.37T AUM 44.26% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.88T AUM 44.46% 1-Year Est. Return

Portolan Capital Management's CSTL Position: Q2 2026 in Review

Portolan Capital Management reduced its Castle Biosciences (CSTL) stake by 76% in Q2 2026, selling an estimated $22.8M and leaving 328,818 shares worth $7.84M. The position accounts for 0.29% of the portfolio, ranked #95.

Portolan Capital Management first reported a position in CSTL in Q3 2019 and has held it in 24 quarters since. The position peaked at $67.3M in Q4 2025. 177 funds tracked by Wall St. Rank hold CSTL as of Q2 2026.

  • Portolan Capital Management held 328,818 shares of Castle Biosciences worth $7.84M as of Q2 2026.
  • Portolan Capital Management sold 1,021,465 Castle Biosciences shares in Q2 2026, an estimated $22.8M.
  • Castle Biosciences made up 0.29% of Portolan Capital Management's portfolio in Q2 2026, its #95 holding.
  • Portolan Capital Management first reported a position in Castle Biosciences in Q3 2019 and has held it in 24 quarters since.
  • Portolan Capital Management's Castle Biosciences position peaked at $67.3M in Q4 2025.
  • 177 funds tracked by Wall St. Rank held Castle Biosciences as of Q2 2026.

Based on Portolan Capital Management's 13F filing for Q2 2026, filed 14 Aug 2026.