CTNNB1 Mutations in Ovarian Microcystic Stromal Tumors: Identification of a Novel Deletion Mutation and the Use of Pyrosequencing to Identify Reported Point Mutation

KIYONG NA; EUN KYUNG KIM; WONJUN JANG; HYUN-SOO KIM

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Figure 1.
Pathological (A to H) and immunohistochemical (I to L) findings. Case 1. The mass is relatively well-circumscribed and lobulated. The solid portion of the tumor is firm and tan-to-white. A few hemorrhagic areas are noted (A). Low-power view reveals round-to-ovoid nests of tumor cells containing variable-sized, irregular-shaped cysts and hyalinized stroma (B). Medium-power view displays microcysts, aggregates of benign-appearing tumor cells, and intervening hyalinized stroma (C). High-power view reveals round, small, bland nuclei and clear-to-eosinophilic cytoplasm (D). Case 2. Scanning view shows large areas of hemorrhage and fibrin deposition (lower third) (E). Tumor cells showing a solid growth pattern are admixed with hyalinizing stroma (F). Several areas exhibiting moderate-to-severe nuclear atypia (G) are located adjacent to intratumoral hemorrhage (H). Immunostaining results. Tumor cell nuclei show diffuse and strong β-catenin (I and J) and cyclin D1 (K) immunoreactivity. The Ki-67 labeling index is low (L).
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Figure 2.
Results of Mutation Analysis. Sequence chromatograms and pyrograms showing point mutations in CTNNB1. In Case 1, a heterozygous missense mutation is detected in CTNNB1 exon 3 of codon 41 (c.122C>T; p.T41I) (A). Consistent with this result, pyrosequencing reveals that thiamine was aberrantly increased up to 59% at codon 41 (B). Sequence chromatogram displaying a novel deletion mutation in CTNNB1. Case 2 exhibits a heterozygous deletion mutation (c.88_99delTACCTGGACTCT). This mutation leads to the loss of 4 consecutive amino acids (p.Y30_S33del) (C).