Lymphoid enhancer-binding factor 1 (LEF1) immunostaining as a surrogate for β-catenin (CTNNB1) mutations

Abstract

Aims: Mutations affecting exon 3 of the β-catenin (CTNNB1) gene result in constitutive activation of WNT signalling and are a diagnostic hallmark of several tumour entities including desmoid-type fibromatosis. They also define clinically relevant tumour subtypes within certain entities, such as endometrioid carcinoma. In diagnostics, β-catenin immunohistochemistry is widely used as a surrogate for CTNNB1 mutations. Yet, it is often difficult to assess in practice, given that the characteristic nuclear translocation may be focal or hard to distinguish from the spillover of the normal membranous staining.

Methods: We therefore examined lymphoid enhancer-binding factor 1 (LEF1) immunostaining, a nuclear marker of WNT activation that serves as a potential surrogate for CTNNB1 mutations.

Results: In a cohort of endometrial carcinomas with known mutation status (n=130) LEF1 was 85% accurate in predicting CTNNB1 mutation status (64% sensitivity, 90% specificity) while β-catenin was 76% accurate (72% sensitivity; 77% specificity). Across a variety of entities characterised by CTNNB1 mutations as putative drivers, we found diffuse and strong expression of LEF1 in 77% of cases. LEF1 immunostaining proved easier to interpret than β-catenin immunostaining in 54% of cases, more difficult in 1% of cases and comparable in the remaining cases.

Conclusion: We conclude that LEF1 immunostaining is a useful surrogate marker for CTNNB1 mutations. It favourably complements β-catenin immunohistochemistry and outperforms the latter as a single marker.

Keywords: CARCINOMA; ENDOMETRIUM; Genes, Neoplasm; IMMUNOHISTOCHEMISTRY.

Figure 1. LEF1 and β-catenin in endometrial carcinoma. (A) negativity of LEF1; (B) membranous positivity of β-catenin and partial nuclear positivity, rendering a classification difficult; (C) strong nuclear positivity of LEF1; (D) strong nuclear, cytoplasmic and membranous positivity of β-catenin. LEF1, lymphoid enhancer binding factor 1.

Figure 2. Survival curves LEF1 and β-catenin immunohistochemistry; (A) LEF1 relapse-free survival (RFS) (p<0.05); (B) β-catenin RFS (p<0.05); (C) LEF1 overall survival (OS) (p<0.05); (D) β-catenin OS (p<0.13). LEF1, lymphoid enhancer binding factor 1; IHC, immunohistochemistry.

Figure 3. Survival curves CTNNB1; (A) relapse-free survival (p<0.27); (B) overall survival (p<0.05).

Figure 4. Overall survival by CTNNB1 mutation status in the The Cancer Genome Atlas data set (p<0.05).

Figure 5. (A–C) Desmoid type fibromatosis: (A) H&E showing classic bland spindle cell morphology; (B) nuclear positivity of LEF1, (C) nuclear and cytoplasmic positivity of β-catenin. (D–F) Solid pseudopapillary tumour of the pancreas (SPN): (D) H&E staining, SPN on the right side, normal pancreas on the left; (E) nuclear positivity of LEF1 in SPN while normal pancreas is negative, (F) nuclear and cytoplasmic positivity of β-catenin in SPN as compared with membranous positivity in normal pancreatic tissue. (G–I) Intestinal adenocarcinoma: (G) intestinal differentiated adenocarcinoma; (H) infiltrative carcinoma is negative for LEF1; (I) strong nuclear and cytoplasmic positivity of the adenocarcinoma for β-catenin. LEF1, lymphoid enhancer binding factor 1.