EIF1AX Mutation in a Patient with Hürthle Cell Carcinoma

EIF1AX mutation in thyroid nodules: a histopathologic analysis of 56 cases in the context of institutional practices

EIF1AX mutation has been identified as a driver mutation for papillary thyroid carcinoma (PTC) by The Cancer Genome Atlas (TCGA) study. Subsequent studies confirmed this mutation in PTC and Anaplastic Thyroid Carcinoma (ATC) but also reported EIF1AX mutation in Follicular nodular disease (FND) and benign thyroid nodules. In this study, we review thyroid nodules with EIF1AX mutation from two institutions: a tertiary care hospital (YNHH, n = 22) and a major cancer referral center (MSKCC, n = 34) and report the varying histomorphology in the context of additional genetic abnormalities and institutional practices. Pathology diagnoses were reviewed according to the WHO 5th edition and correlated with the type of EIF1AX mutation and additional concurrent molecular alterations, if any. Most cases were splice site type mutations. Cases consisted of 9 FND, 7 follicular (FA) or oncocytic adenomas (OA), 2 non-invasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) and 38 follicular-cell derived thyroid carcinomas. Of 8 cases with isolated EIF1AX mutation, 7 were FND, FA or OA (88%) and one was an oncocytic carcinoma (12%). Of 12 cases with EIF1AX and one additional molecular alteration, 9 (75%) were FND, FA or OA, 2 (17%) were NIFTPs and one (8%) was a poorly differentiated thyroid carcinoma. All 36 cases with EIF1AX mutation and ≥ 2 molecular alterations were malignant (100%) and included TP53 and TERT promoter mutations associated with ATC (n = 8) and high-grade follicular cell-derived non-anaplastic carcinoma (HGC, n = 2). Isolated EIF1AX mutation was noted only in thyroid nodules seen at YNHH and were predominantly encountered in benign thyroid nodules including FND. Accumulation of additional genetic abnormalities appears to be progressively associated with malignant tumors.

EIF1AX mutation in thyroid tumors: a retrospective analysis of cytology, histopathology and co-mutation profiles

Background

The EIF1AX mutation has been identified in various benign and malignant thyroid lesions, with a higher prevalence in poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma, especially when combined with RAS or TP53 mutation. However, data and clinical significance of EIF1AX mutations in thyroid nodules is still limited. We investigated the prevalence of EIF1AX mutations and co-mutations in cytologically indeterminate thyroid nodules at our institution.

Methods

A 5-year retrospective analysis was performed on surgically resected thyroid nodules with identified EIF1AX mutations on molecular testing with ThyroseqV3®. Mutation type and presence of co-mutations were correlated with histopathologic diagnosis and clinical characteristics. Histopathology diagnoses were subsequently categorized as benign, borderline, malignant or aggressive malignant (≥ 10% PDTC component). Chi-square test was used to compare the malignancy associations of the: 1) A113_splice mutation compared to non-A113_splice mutations 2) singular A113_splice mutations compared to singular non-A113_splice mutations. Fisher’s Exact Test was used to determine the association of A113_splice mutation with aggressive malignancies compared to non-A113_splice mutations. A p value of 0.05 or less was considered statistically significant.

Results

Out of 1583 patients who underwent FNA, 621 had further molecular testing. 31 cases (5%) harbored EIF1AX mutations. Of these cases, 12 (38.7%) were malignant, 2 (6.5%) were borderline, and 17 (55%) were benign. 4/31 cases (13%) were aggressive malignant (≥ 10% PDTC component). The most prevalent mutation was the A113_splice mutation at the junction of intron 5 and exon 6 (48%). All other mutations, except one, were located at the N-terminal in exon 2. 7/31 cases (22.6%) harbored ≥ 1 co-mutation(s), including 4 RAS, 3 TP53, 1 TERT and 1 PIK3CA, with 86% of them being malignant. All 4 nodules with RAS co-mutations were malignant including one PDTC.

Conclusion

Our study reports the largest cohort of EIF1AX mutations in Bethesda III/IV FNA samples with surgical follow-up to our knowledge. The presence of the EIF1AX mutation confers a 45.2% risk of malignancy (ROM) or borderline after surgery. However, the coexistence of EIF1AX mutations with other driver mutations such as RAS, TERT or TP53 conferred an 86% ROM. While 55% of thyroid nodules were benign at the time of surgery, the possible malignant transformation of these nodules, had they not been resected, is unknown. Finally, 13% of the nodules with EIF1AX mutations were aggressive with a significant PDTC component. These findings can further aid in clinical decisions for patients with thyroid nodules.

Graphic Abstract

Molecular alterations in Hürthle cell neoplasms of thyroid: A fine needle aspiration cytology study with cytology-histology correlation

BACKGROUND

Hürthle cell features are frequently observed on the fine-needle aspiration (FNA) cytology of thyroid nodules and often pose a diagnostic challenge because of a significant overlap between cytomorphologic features seen in benign and malignant lesions. Molecular alterations (MAs) associated with these lesions are not well described. The objective of the current study was to evaluate the molecular profile of Hürthle cell lesions classified as Hürthle cell neoplasm (HCN) on cytologic evaluation.

METHODS

The authors retrospectively reviewed their electronic database for cytologic diagnoses of HCN from January 1, 2017 to March 31, 2020.

RESULTS

In total, 279 cases from 275 patients who had a diagnosis of HCN were included in the study. Molecular testing results were available in 85 cases (51 with MAs and 34 without MAs) and, of those, 42 had histologic follow-up available. Eight of 10 malignant cases had MAs, whereas the remaining 2 cases were negative for MAs. The most frequently encountered predominant genetic alterations or classifier findings were chromosome copy number alterations (n = 15), followed by NRAS (n = 8), KRAS (n = 7), suspicious (n = 6), EIF1AX (n = 4), TSHR (n = 3), gene overexpression (n = 3), positive microRNA classifier (n = 2), and 1 each of BRAF K601E, TERT, and HRAS mutations. One hundred thirty-seven cases had histologic follow-up available; of those, 28 were classified as malignant, and 109 were classified as benign (neoplastic and nonneoplastic). The overall risk of malignancy associated with HCN was 20%, and the risk of HCN with MAs was 25%.

CONCLUSIONS

The cytologic diagnosis of HCN includes various MAs without any obvious trend, and most malignant cases (80%) have some type of MA.

EIF1AX c.338-2A>T splice site mutation in a patient with trabecular adenoma and cytological indeterminate lesion

The EIF1AX gene mutations have been recently associated with papillary thyroid carcinoma and anaplastic thyroid cancer. According with these reports, the gene as been considered as a drive gene for thyroid cancer development. However, the occurrence of these alterations in benign thyroid lesions is not known and is still under investigation. Some authors have already reported the presence of EIF1AX variants in follicular adenomas and hyperplastic nodules. Here, we describe for the first time a case of a man with the EIF1AX c.338-2A>T splice site mutation in an indeterminate FNA lesion with trabecular adenoma at final histology in the absence of other pathogenetic mutations, demonstrating that further studies are required to better understand EIF1AX role in the tumorigenesis of thyroid carcinoma.

Macrofollicular Variant of Follicular Thyroid Carcinoma: A Rare Underappreciated Pitfall in the Diagnosis of Thyroid Carcinoma

Background: Follicular-patterned thyroid nodules predominantly composed of macrofollicular structures without nuclear atypia are generally regarded as benign (i.e., hyperplastic nodules or follicular adenomas). In line with this concept, fine-needle aspiration cytology (FNAC) also assigns a benign connotation to the presence of macrofollicular structures, unless thyrocytes present papillary thyroid carcinoma (PTC)-related nuclear features that raise the possibility of a macrofollicular variant of PTC. However, cases showing macrofollicular architecture, capsular invasion, and no PTC features can also be observed. Methods: We describe the clinical, cytological, histological, and molecular genetic features of four cases of encapsulated follicular neoplasms that presented histologically with a predominant (>70%) macrofollicular architecture, but which also showed clear signs of capsular invasion, and thus were classified as macrofollicular variant of follicular thyroid carcinoma (MV-FTC). Results: Cytologically, macrofollicular structures were identified in all cases, leading to a benign FNAC diagnosis in three of the four cases. Due to increasing nodule size, thyroidectomy was performed in all cases. Histology showed focal and limited capsular invasion, without vascular invasion. Next-generation sequencing (custom 394 gene panel) of each tumor compared with matched normal DNA revealed a total of 7 somatic variants, including dual (likely biallelic) mutations in the DICER1 gene in 2 patients. The clinical outcome was excellent in all cases. Conclusions: Similar to the classical minimally invasive follicular thyroid carcinoma, MV-FTC appears to behave indolently. MV-FTC has a high rate of false-negative FNAC results, but MV-FTC is very rare (<0.05% of all thyroidectomies) and apparently has an indolent behavior. Further studies comprising larger series are necessary to better clarify the biology of this diagnostically challenging rare tumor.

Mutation profiles of follicular thyroid tumors by targeted sequencing

BACKGROUND

One of the major challenges remaining in the classification of thyroid tumor is the determination of whether a nodule is benign or malignant. We aimed to characterize the mutational profiles of follicular thyroid tumor and to identify markers with potential diagnostic and prognostic implications.

METHODS

Targeted sequencing with a panel of 18 thyroid cancer-related genes was performed on 48 tissue samples from follicular thyroid adenoma (FTA), 32 follicular tumors of uncertain malignant potential (FT-UMP), 17 well-differentiated tumors of uncertain malignant potential (WDT-UMP) and 53 samples from follicular thyroid carcinoma (FTC). The correlation of mutation profiles and clinicopathological features and prognosis were also analyzed.

RESULTS

We identified 95 nonsilent mutations spanning 14 genes. Specifically, TERT promoter (TERTp) mutations were exclusively detected in FTC. A total of 80% EIF1AX exon 2 mutations (4/5) and 75% TSHR mutations (3/4) occurred in FTA, whereas the rest of them occurred in FT-UMP. KRAS mutations and TP53 mutations were only presented in borderline or malignant tumors. H/N-RAS mutations were detected in all four subtypes, but were most commonly found in WDT-UMP (p = 0.031). All N-RAS mutations were located at codon 61. BRAF V600E and RET fusion were absent in the entire cohort. In FTC cases, EIF1AX mutations were all located at intron 5/exon 6 and correlated with advanced disease (p = 0.032). Both EIF1AX and TERTp mutations predicted shorter disease-free survival (p = 0.007, p = 0.024, respectively). Further analysis revealed that TERTp mutations were correlated with shorter disease-free survival in patients with minimally invasive /encapsulated angioinvasive FTC (p = 0.017), but not in those with widely invasive FTC (p = 0.297).

CONCLUSION

TERTp, EIF1AX, TSHR, H/N/K-RAS and TP53 mutations may have diagnostic or prognostic potential in follicular thyroid tumors. TERTp mutations may predict a poor outcome in patients with minimally invasive/encapsulated angioinvasive FTC.

The role of EIF1AX in thyroid cancer tumourigenesis and progression

PURPOSE

The EIF1AX gene was recently described as a new thyroid cancer-related gene. Its mutations were mainly reported in poorly differentiated (PDTC) and anaplastic thyroid cancers (ATC), but also in well-differentiated thyroid cancer (WDTC) and in benign thyroid lesions, although less frequently. Our aim was to address whether EIF1AX mutations are present in the different stages of thyroid tumourigenesis (from hyperplasia to well-differentiated and to poorly differentiated/undifferentiated lesions), and to clarify its role in this process.

METHODS

We analysed the EIF1AX gene in a series of 16 PDTC and ATC cases with coexistent well-differentiated regions and/or benign lesions. In EIF1AX mutant cases we also assessed the presence of RAS genes mutations.

RESULTS

We identified the mutation p.Ala113_splice in the EIF1AX gene in two PDTCs (neither present in the well-differentiated counterparts nor in the benign areas). One of these tumours also evidenced the mutation p.Glu61Arg in NRAS in both poorly and well-differentiated regions, further suggesting that the EIF1AX p.Ala113_splice mutation could be associated with tumoural progression. In another patient we did not find any EIF1AX alteration in the PDTC component, but we detected the EIF1AX p.Gly6_splice mutation in the PTC area (both regions were RAS wild-type). This mutation did not seem to be related with dedifferentiation.

CONCLUSIONS

According to our results, distinct mutations on EIF1AX may be related to different phenotypes/behaviours. Despite being a small series, which reflects the difficulty in retrieving PDTC and ATC surgical samples with well-differentiated and/or benign areas, our study may provide new insights into thyroid cancer tumourigenesis and dedifferentiation.