Immunohistochemical staining of LEF-1 is a useful marker for distinguishing WNT-activated medulloblastomas

Diagnostic insights into solid pseudopapillary neoplasms of the pancreas: a decade of experience with pediatric representation

BACKGROUND

Solid pseudopapillary neoplasms (SPNs) of the pancreas are rare, low-grade malignancies that predominantly affect young females. Their diagnosis is often facilitated by a characteristic histomorphological pattern and immunohistochemical profile. However, diagnostic challenges persist, especially in pediatric and atypical presentations. Recent attention has focused on the diagnostic value of CD99 and LEF1 in distinguishing SPNs from other pancreatic neoplasms.

OBJECTIVE

To evaluate the diagnostic accuracy and utility of CD99 and LEF1 as immunohistochemical markers for SPNs.

METHODS

A retrospective analysis of 60 SPN cases diagnosed between 2015 and 2024 was performed. Histopathological features were systematically reviewed, and immunohistochemical staining for CD99, LEF1, β-catenin, Cyclin D1, PR, Ki-67 was evaluated. Immunohistochemical marker interpretation was standardized using internally validated thresholds informed by existing literature: CD99 was considered positive with ≥ 10% cytoplasmic staining exhibiting paranuclear accentuation; β-catenin positivity was defined by ≥ 5% nuclear localization; Cyclin D1 by ≥ 10% moderate-to-strong nuclear staining; and progesterone receptor (PR) expression by ≥ 1% nuclear positivity, consistent with hormone receptor evaluation guidelines. Marker expression was statistically analyzed for their associations.

RESULTS

SPNs exhibited a strong female predilection (F:M ratio ≈ 7:1), with a mean age of 32.5 years. Pediatric cases (n = 4) displayed higher mean expression of CD99 (73.8%) and LEF1 (86.5%) compared to adults. CD99 showed cytoplasmic positivity with paranuclear accentuation in 96.7% of cases, while LEF1 demonstrated nuclear staining in 91.7%. β-catenin nuclear localization was observed in 95% of tumors, reflecting Wnt/β-catenin pathway activation. Cyclin D1 and PR were expressed in 90% and 88.3% of cases, respectively. Co-expression of β-catenin, CD99, LEF1, Cyclin D1, and PR was observed in 73.3% of tumors. CD99 and LEF1 inversely correlated with tumor size and proliferative activity (Ki-67), whereas Cyclin D1 and Ki-67 positively correlated with tumor size and lymphovascular invasion (LVI). Pediatric tumors generally exhibited favorable profiles, with limited evidence of LVI.

CONCLUSION

SPNs present with distinctive immunohistochemical signatures that are critical for accurate diagnosis, particularly in morphologically ambiguous or pediatric cases. CD99 and LEF1 are highly sensitive markers that, in combination with β-catenin and Cyclin D1, enhance diagnostic precision. These findings emphasize the central role of Wnt/β-catenin signaling in SPN pathogenesis and underscore the importance of integrating clinicopathological and molecular data for comprehensive tumor assessment.

Wnt/β-catenin pathway activation is associated with glucocorticoid secretion in adrenocortical carcinoma, but not directly with immune cell infiltration

Background

In advanced adrenocortical carcinoma (ACC), the response rate to immune checkpoint inhibition (ICI) is only ~15%. Glucocorticoid (GC) secretion and the activation of the Wnt/β-catenin pathway have been suggested to contribute to low tumour immune cell infiltration. The transcription factor lymphoid enhancer factor 1 (LEF-1) transduces β-catenin (CTNNB1)-mediated transcriptional activation.

Objective

To understand the contribution of Wnt/β-catenin pathway activation and glucocorticoid receptor (GR) signalling to the immunologically cold ACC tumour microenvironment.

Methods

Semi-quantitative immunohistochemistry (IHC) of β-catenin (CTNNB1), LEF-1, GR and T cell markers CD3, CD4, CD8, Fox P3 in 59 ACC samples. Targeted RNA expression analysis of 354 immune-related genes in 58 additional ACC tissue specimens. Correlative analyses with clinical data.

Results

Nuclear LEF-1 and CTNNB1 protein expression were positively correlated in ACC tissue (Pearson R2 = 0.1283, p=0.0046). High, moderate and low protein expression was detected in 24.1%, 53.2% and 19.3% of samples for LEF-1, and 30.6%, 43.5% and 19.3% for CTNNB1, respectively. We found higher LEF-1 expression in GC-secreting tumours which did not differ from inactive tumours in terms of GR expression. T cell markers, as evaluated by IHC, were not associated with expression of Wnt/β-catenin pathway markers. At RNA level, tumours with high LEF-1 expression showed significant downregulation of 37 transcripts (including 8 involved in antigen presentation). High LEF-1 expression levels correlated with worse overall survival in this cohort. This was not the case for CTNNB1 and GR.

Conclusion

Lef-1 expression is useful as a biomarker of activated Wnt/β-catenin signalling in ACC. Wnt/β-catenin pathway activation was not associated with reduced immune cell markers in ACC but GC secretion and may be related to tumoural antigen presentation.

Diagnostic utility of LEF1 and β-catenin in WNT pathway tumors with CTNNB1 mutation

OBJECTIVE

This study aimed to compare the expression of lymphoid enhancer factor 1 (LEF1) and β-catenin in basal cell adenoma (BA), desmoid-type fibromatosis (DF), and pancreatic solid pseudopapillary neoplasm (SPN) to evaluate their diagnostic utility in tumors associated with the WNT/β-catenin signaling pathway harboring the mutation of CTNNB1 gene 3 exon.

METHODS

Eighty tumor patients, including 26 BAs, 30 DFs, and 24 SPNs, were analyzed. Immunohistochemical staining was identified positive (nuclear staining of LEF1 and β-catenin in > 50% of tumor cells). The diagnostic rate of LEF1 alone, β-catenin alone, and their combination were compared for each tumor type and all patients.

RESULTS

Compared to β-catenin, when LEF1 alone was used for diagnosis, the diagnostic rate increased by 46.16% for BA, 16.67% for SPN, and 11.25% for all patients, but decreased by 23.34% for DF. The combined use of β-catenin and LEF1 significantly increased the diagnostic ratio in BA (46.16%), SPN (16.67%), and all patients (21.25%), but only marginally in DF (3.33%). In terms of all WNT pathway tumors with CTNNB1 gene mutation encompassed by our study, statistical analysis revealed no significant difference between LEF1 alone and β-catenin alone. However, their combined application was highly significant (P = 0.001) .

CONCLUSION

While β-catenin is commonly used as a marker for WNT pathway tumors, its variable expression and localization can be challenging for diagnosis. Our study emphasizes the importance of LEF1 as a complementary marker to β-catenin in diagnosing BA, DF, SPN, and other WNT pathway tumors activated by exon 3 CTNNB1 gene mutation. The combined use of LEF1 and β-catenin enhances diagnostic accuracy and may help the identification of these tumor types.

Single-Cell RNA Sequencing Reveals LEF1-Driven Wnt Pathway Activation as a Shared Oncogenic Program in Hepatoblastoma and Medulloblastoma

(1) Background: Hepatoblastoma and medulloblastoma are two types of pediatric tumors with embryonic origins. Both tumor types can exhibit genetic alterations that affect the β-catenin and Wnt pathways; (2) Materials and Methods: This study used bioinformatics and integrative analysis of multi-omics data at both the tumor and single-cell levels to investigate two distinct pediatric tumors: medulloblastoma and hepatoblastoma; (3) Results: The cross-transcriptome analysis revealed a commonly regulated expression signature between hepatoblastoma and medulloblastoma tumors. Among the commonly upregulated genes, the transcription factor LEF1 was significantly expressed in both tumor types. In medulloblastoma, LEF1 upregulation is associated with the WNT-subtype. The analysis of LEF1 genome binding occupancy in H1 embryonic stem cells identified 141 LEF1 proximal targets activated in WNT medulloblastoma, 13 of which are involved in Wnt pathway regulation: RNF43, LEF1, NKD1, AXIN2, DKK4, DKK1, LGR6, FGFR2, NXN, TCF7L1, STK3, YAP1, and NFATC4. The ROC curve analysis of the combined expression of these 13 WNT-related LEF1 targets yielded an area under the curve (AUC) of 1.00, indicating 100% specificity and sensitivity for predicting the WNT subtype in the PBTA medulloblastoma cohort. An expression score based on these 13 WNT-LEF1 targets accurately predicted the WNT subtype in two independent medulloblastoma transcriptome cohorts. At the single-cell level, the WNT-LEF1 expression score was exclusively positive in WNT-medulloblastoma tumor cells. This WNT-LEF1-dependent signature was also confirmed as activated in the hepatoblastoma tumor transcriptome. At the single-cell level, the WNT-LEF1 expression score was higher in tumor cells from both human hepatoblastoma samples and a hepatoblastoma patient-derived xenotransplant model; (4) Discussion: This study uncovered a shared transcriptional activation of a LEF1-dependent embryonic program, which orchestrates the regulation of the Wnt signaling pathway in tumor cells from both hepatoblastoma and medulloblastoma.

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

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.