The enlightenments from ITMIG Consensus on WHO histological classification of thymoma and thymic carcinoma: refined definitions, histological criteria, and reporting

Machine learning for predicting the prognosis of patients with thymoma and thymic carcinoma

Background

Thymoma and thymic carcinoma are the most common tumors of the anterior mediastinum. However, there are little research on applying machine learning (ML) approaches to the prognostic prediction of thymoma and thymic carcinoma. The study aims to develop predictive models utilizing ML techniques to accurately forecast the 5-year survival of patients with thymoma and thymic carcinoma.

Methods

Patients with malignant thymic neoplasms were identified in the Surveillance, Epidemiology, and End Results (SEER) 17 database, and their demographic and clinicopathological characteristics were collected. ML classifiers, including elastic net regularized logistic regression, random forest (RF), non-linear support vector machine (SVM), extreme gradient boosting (XGBoost) machine, and categorical boosting (CatBoost) were trained. The hyper-parameter of the algorithms was optimized by a grid search with five repeats of 10-fold cross-validation. Ensemble models were built based on the three algorithms with the highest area under the receiver operator characteristic (ROC) curve (AUC) in the validation set. The best model among the single models and ensemble model was selected as the final model. Calibration curve and decision curve were adopted to evaluate the calibration performance and clinical utility. For comparison, we constructed a baseline model consisting of age and Masaoka stages using logistic regression.

Results

After data cleaning, 1,363 patients and 841 patients were included in the overall survival (OS) dataset and disease-specific survival (DSS) dataset, respectively. CatBoost [AUC: 0.755; 95% confidence interval (CI): 0.698-0.811] had the best performance in the OS prediction for the original dataset. The ensemble model achieved the highest prognostic efficiency for the original dataset, with an AUC of 0.833 (95% CI: 0.765-0.901). Calibration showed favorable goodness of fit and was further verified with the Hosmer-Lemeshow test (CatBoost: χ2=12.63, P=0.13; ensemble model: χ2=7.61, P=0.47). The decision curve showed that the final model provided a high net benefit. The model could significantly distinguish the prognosis of patients (all P values <0.001). Finally, World Health Organization (WHO) histological classification, Masaoka stage, and age were the variables that significantly contributed to the models' prediction of OS and DSS.

Conclusions

We trained ML-based predictive models that could accurately predict the 5-year OS and DSS of patients with thymoma and thymic carcinoma.

Thymic epithelial tumours in 51 dogs: Histopathologic and clinicopathologic findings

Canine thymic epithelial tumours (TET) are uncommon and little is known about their behaviour. Previous attempts at histologic classification have varied, and as such reliable prognostic information is unavailable. The aim of this retrospective multi-institutional study was to evaluate cases of canine TETs, irrespective of subtype, in order to identify useful histopathologic and clinicopathologic prognostic factors. Cases were included if the tumour arose from the cranial mediastinum and a diagnosis of TET was made on the basis of histopathology. Fifty-one dogs were included. In addition to clinicopathologic data, histology samples were reviewed for the following features: mitotic count, percentage of necrosis, presence of Hassall's corpuscles, lymphocytic infiltrate, cellular pleomorphism and vascular or capsular invasion. The median survival time for all dogs was 449 days. The 1- and 2-year survival rate was 52.6% and 26.3% respectively. On multivariable analysis surgical excision of the thymic tumour was associated with significantly prolonged survival; the presence of metastasis, myasthenia gravis and moderate or marked cellular pleomorphism were associated with significantly reduced survival. Additional studies are needed to further evaluate prognostic factors to aid treatment recommendations.

Characteristics and outcomes of thymomas in Latin America: Results from over 10 years of experience (CLICaP-LATimus)

BACKGROUND

Thymomas are a group of rare neoplasms of the anterior mediastinum. The objective of this study was to describe the demographics, clinical characteristics and treatment approaches in Latin America.

METHODS

This was a retrospective multicenter cohort study including patients with histologically proven thymomas diagnosed between 1997 and 2018. Demographics, clinicopathological characteristics and therapeutic outcomes were collected locally and analyzed in a centralized manner.

RESULTS

A total of 135 patients were included. Median age at diagnosis was 53 years old (19-84), 53.3% (n = 72) of patients were female and 87.4% had an ECOG performance score ranging from 0-1. A total of 47 patients (34.8%) had metastatic disease at diagnosis. Concurrent myasthenia gravis occurred in 21.5% of patients. Surgery was performed in 74 patients (54.8%), comprising 27 (20%) tumorectomies and 47 (34.8%) thymectomies. According to the Masaoka-Koga system, overall survival (OS) at five-years was 73.4%, 63.8% and 51%, at stages I-II, III-IVA and IVB, respectively (p = 0.005). Furthermore, patients with low lactate dehydrogenase (LDH) (≤373 IU/L) at baseline and myasthenia gravis concurrence showed significantly better OS (p = 0.001 and p = 0.008, respectively). In multivariate analysis, high LDH levels (HR 2.8 [95% confidence interval [CI]: 1.1-7.8]; p = 0.036) at baseline and not performing a surgical resection (HR 4.1 [95% CI: 1.3-12.7]; p = 0.016) were significantly associated with increased risk of death.

CONCLUSIONS

Our data provides the largest insight into the clinical characteristics and outcomes of patients with thymomas in Latin America. Survival in patients with thymomas continues to be very favorable, especially when subjected to adequate local control.

GOECP/SEOR radiotherapy guidelines for thymic epithelial tumours

Thymic epithelial tumours (TET) are rare, heterogeneous neoplasms that range from resectable indolent tumours to aggressive thymic carcinomas with a strong tendency to metastasize. The pathological diagnosis is complex, in part due to the existence of several different classification systems. The evidence base for the management of TETs is scant and mainly based on non-randomised studies and retrospective series. Consequently, the clinical management of TETs tends to be highly heterogenous, which makes it difficult to improve the evidence level. The role of technological advances in the field of radiotherapy and new systemic therapies in the treatment of TETs has received little attention to date. In the present clinical guidelines, developed by the GOECP/SEOR, we review recent developments in the diagnosis and classification of TETs. We also present a consensus-based therapeutic strategy for each disease stage that takes into consideration the best available evidence. These guidelines focus primarily on the role of radiotherapy, including recent advances, in the management of TETs. The main aim of this document is to promote the standardisation of clinical practice and lay the foundations for future studies to clarify the main unresolved questions related to the optimal management of TET.

[Thymoma and squamous thymic carcinoma diagnosis; experience from the RYTHMIC network]

The RYTHMIC network, supported by the French National Cancer Institute is dedicated to the management of patients with thymic epithelial tumors through regional and national multidisciplinary tumor boards. Tumor board decisions are based on the initial pathology diagnoses. However, following clinical inclusion in the network, a central pathology review is organized, implicating a panel of pathologists, for histotype and stage classification, which is different from a classical second opinion from pathologist to pathologist for a difficult case. Thanks to the participation of all French pathologists, more than 1000 cases have been reviewed by the panel. The aim of this review is to share with the French pathology community, the experience of the group. It underlines the importance of macroscopy and surgeon-pathologist involvement to allow a good central review, the main histopathological and immunophenotypical patterns of the most frequent thymomas and thymic carcinoma types, the differential diagnoses, as well as the difficulties for the panel to reproducibly assess on slides, stage, for some cases.

Perioperative risk factors for occurrence of myasthenia gravis after thymectomy in patients with thymoma

OBJECTIVES

The goal of this study was to identify the relationship between clinical characteristics and the occurrence of postoperative myasthenia gravis (PMG) in patients with thymomas and to further identify the relationship between PMG and prognosis.

METHODS

Thymoma patients who had surgery at the First Affiliated Hospital of Sun Yat-sen University between July 2004 and July 2016 were reviewed and those who had no previous symptoms of myasthenia gravis were selected for further investigation. In total, 229 patients were included in the study; their clinical characteristics were gathered and analysed.

RESULTS

Among the 229 patients, 19 (8.3%) had PMG. The time between the operation and the onset of myasthenia gravis was 134 days on average (range 2-730 days). Patients experiencing PMG showed a lower rate of complete thymoma resection (73.7% vs 91.4%; P = 0.014) and total thymectomy (63.2% vs 82.9%; P = 0.035) compared with those who did not. Univariable and multivariable logistic regression revealed that thymomectomy [odds ratio (OR) 2.81, 95% confidence interval (CI) 1.02-7.77; P = 0.047] and incomplete tumour resection (OR 3.79, 95% CI 1.20-11.98; P = 0.023) were associated with the occurrence of PMG. Multivariable Cox regression showed that the PMG was not related to overall survival (P = 0.087).

CONCLUSIONS

This study revealed that incomplete tumour resection and thymomectomy were independent risk factors for PMG in thymoma patients with no previous history of myasthenia gravis.

Deciphering tissue-based proteome signatures revealed novel subtyping and prognostic markers for thymic epithelial tumors

Thymic epithelial tumors (TETs) belong to a group of tumors that rarely occur, but have unresolved mechanisms and heterogeneous clinical behaviors. Current care of TET patients demands biomarkers of high sensitivity and specificity for accurate histological classification and prognosis management. In this study, 134 fresh‐frozen tissue samples (84 tumor, 40 tumor adjacent, and 10 normal thymus) were recruited to generate a quantitative and systematic view of proteomic landscape of TETs. Among them, 90 samples were analyzed by data‐independent acquisition mass spectrometry (DIA‐MS) leading to discovery of novel classifying molecules among different TET subtypes. The correlation between clinical outcome and the identified molecules was probed, and the prioritized proteins of interest were further validated on the remaining samples (n = 44) via parallel reaction monitoring (PRM) as well as immunohistochemical and confocal imaging analysis. In particular, two proteins, the cellular mRNA deadenylase CCR4 (carbon catabolite repressor 4)‐NOT (negative on TATA) complex subunit 2/9 (CNOT2/9) and the serine hydroxymethyltransferase that catalyzes the reversible interconversions of serine and glycine (SHMT1), were found at dramatic low levels in the thymic epithelia of more malignant subtype, thymic squamous cell carcinoma (TSCC). Interestingly, the mRNA levels of these two genes were shown to be closely correlated with prognosis of the TET patients. These results extended the existing human tissue proteome atlas and allowed us to identify several new protein classifiers for TET subtyping. Newly identified subtyping and prognosis markers, CNOT2/9 and SHMT1, will expand current diagnostic arsenal in terms of higher specificity and prognostic insights for TET diagnosis and management.

EWSR1 translocation in primary hyalinising clear cell carcinoma of the thymus

AIMS

In thymic carcinomas, focal clear cell change is a frequent finding. In addition to a prominent, diffuse clear cell morphology, some of these carcinomas show an exuberant hyalinised extracellular matrix, and therefore probably represent a separate entity. However, a characteristic genomic alteration remains elusive. We hypothesised that, analogous to hyalinising clear cell carcinomas of the salivary gland, hyalinising clear cell carcinomas of the thymus might also harbour EWSR1 translocations.

METHODS AND RESULTS

We identified nine archived cases of thymic carcinoma with focal clear cell features and two cases that showed remarkable hyalinised stroma and prominent, diffuse clear cell morphology. These two cases expressed p40 and were negative for Pax8, CD5, and CD117. Programmed death-ligand 1 was highly positive in one case (70%), and negative in the other one. EWSR1 translocation was identified in both cases of hyalinising clear cell carcinoma, and was absent in all nine carcinomas that showed clear cell features without substantial hyalinisation. In one of the EWSR1-translocated cases, a fusion between exon 13 and exon 6 of EWSR1 and ATF1, respectively was identified by next-generation sequencing.

CONCLUSIONS

These findings suggest that the EWSR1 translocation and possibly the EWSR1-ATF1 fusion might be unifying genomic alterations for thymic clear cell carcinomas with prominent hyalinised stroma, for which we propose the term 'hyalinising clear cell carcinoma of the thymus'. Because the immunophenotype is unspecific, testing for the EWSR1 translocation might be helpful in discriminating this entity from other thymic neoplasms or metastases, in particular those with clear cell change.

[Pure red cell aplasia of the bone marrow in combination with thymoma. A literature review and own data]

Eight patients were observed with a rare combination of thymoma and pure red cell aplasia of bone marrow (PRCA), of which seven women were between 44 to 68 years old. The diagnosis of PRCA was established before the detection of thymoma in 1 patient, simultaneously in 3, after - in 4. Seven patients underwent timomectomy. The weight of removed thymomas was from 200 to 780 grams. Morphological type A thymoma variant (spindle cell) was installed in 2 patients, type B1 - in 2, type B2 - in 2, type B3 - in 2. Complete remissions were obtained using cyclophosphamide and cyclosporin in 5 patients, lasting from 6 months to 7 years. The results of immunological studies with the identification of non - hemolytic antibodies to the proteolytic antigen (Pr1d) on the erythrocyte membrane in 4 patients are presented. Of these, two studied patients simultaneously detected antibodies to the Pr1d antigen and the interspecific antigen of mammalian erythroblasts (IAME). It is shown that the lifespan of red blood cells are not changed. The direct Coombs test was negative in 5 patients, but with the help of aggregate hemaglutination test and enzyme immunoassay, antibodies were detected on the surface of erythrocytes. The pathogenesis of this combination of diseases remains unclear and needs to be elucidated.

Pathological discrepancies in the diagnosis of thymic epithelial tumors: the Tallinn-Lyon experience

Background

Thymic epithelial tumors are rare thoracic tumors for which pathological diagnosis is challenging due to the definition of multiple subtypes, tumor heterogeneity, and variations in interobserver reproducibility. In this study, we aimed at analyzing the quality of pathological reporting in line with the consistency between initial diagnosis and final diagnosis after expert review through a collaboration between the largest thoracic oncology center in Estonia, and one expert center in France.

Methods

Hospital electronic database and pathology databases from the Tallinn North Estonia Medical Centre were searched for thymic and mediastinal tumors from 2010 to 2017. Pathology specimens were referred to the Pathology Department of the Lyon University hospital. Overall, 55 tissue specimens from 49 patients were included.

Results

From pathology reports, tumor size, diagnosis, and invasion had been mentioned in ≥80% of cases, while resection status and staging were assessed in only 48% and 17% of cases, respectively. The initial diagnosis was consistent with that of the review in 60% of cases. Diagnostic concordance for thymoma subtypes was low (Cohen's kappa 0.34, 95% CI: 0.16-0.52). Overall, a major change in the management of 8 (16%) patients had to be made after pathological review: 3 patients had a normal thymus according to the reference centre, while thymoma B1 or B2 had been diagnosed locally; 5 additional patients had a final diagnosis of non-thymic tumor.

Conclusions

Implementing structured pathology reports may help to decrease discrepancies in the diagnosis of thymic epithelial tumors. The development of expert networks is an opportunity to improve diagnosis and patient care, particularly in regard to rare cancers.

Extended resections of large thymomas: importance of en bloc thymectomy

Background

Primary tumors of the thymus are rare; the most common histologic type is thymoma. Most important prognostic factors are anatomical extent of tumor and completeness of surgical resection. Large size has not been directly associated with survival, but is strongly associated with advanced disease and high rates of incomplete resections.

Methods

A retrospective cohort of patients who underwent thymectomy for thymomas of 5 cm or larger at the National Cancer Institute (INCan) of México from January 2005 to December 2016 was analyzed. Primary end-points were rate of complete resection, morbidity and mortality of thymectomy. Secondary end-points were overall survival (OS) and disease-free survival (DFS).

Results

A total of 25 patients were identified and included in the final analysis. Mean age was 56.6 years (27-82 years). Median size of thymoma was 8.3 cm (5-14 cm). Transesternal approach was used in 72% of cases, most of cases (68%) required an extended resection to achieve negative margins. Complete resection was achieved on 23 cases (92%). A 90-day morbidity of 24% and mortality of 8% was found, with a median follow-up of 34.5 months (1-113 months). The only factor associated with OS was completeness of surgical resection (P<0.0001).

Conclusions

Size of thymomas should not be considered as a contraindication for surgical treatment. Our data suggest that extended surgery is feasible even in advanced cases and provides the best chance for cure. Complete resection remains as one of the most important prognostic factor in thymomas and is associated with prolonged DFS and OS.

Paraneoplastic Syndromes and Thymic Malignancies: An Examination of the International Thymic Malignancy Interest Group Retrospective Database

INTRODUCTION

Thymic epithelial tumors (TETs) are associated with paraneoplastic/autoimmune (PN/AI) syndromes. Myasthenia gravis is the most common PN/AI syndrome associated with TETs.

METHODS

The International Thymic Malignancy Interest Group retrospective database was examined to determine (1) baseline and treatment characteristics associated with PN/AI syndromes and (2) the prognostic role of PN/AI syndromes for patients with TETs. The competing risks model was used to estimate cumulative incidence of recurrence (CIR) and the Kaplan-Meier method was used to calculate overall survival (OS). A Cox proportional hazards model was used for multivariate analysis.

RESULTS

A total of 6670 patients with known PN/AI syndrome status from 1951 to 2012 were identified. PN/AI syndromes were associated with younger age, female sex, thymoma histologic type, earlier stage, and an increased rate of total thymectomy and complete resection status. There was a statistically significant lower CIR in the group with a PN/AI syndrome than in the group without a PN/AI syndrome (10-year CIR 17.3% versus 21.2%, respectively [p = 0.0003]). The OS was improved in the group with a PN/AI syndrome compared to the group without a PN/AI syndrome (median OS 21.6 years versus 17.0 years, respectively [hazard ratio = 0.63, 95% confidence interval: 0.54-0.74, p < 0.0001]). However, in the multivariate model for recurrence-free survival and OS, PN/AI syndrome was not an independent prognostic factor.

DISCUSSION

Previously, there have been mixed data regarding the prognostic role of PN/AI syndromes for patients with TETs. Here, using the largest data set in the world for TETs, PN/AI syndromes were associated with favorable features (i.e., earlier stage and complete resection status) but were not an independent prognostic factor for patients with TETs.

Diagnosis of thymic epithelial tumor subtypes by a quantitative proteomic approach

This study shows the first depth proteomic profiling of all TET subtypes and six candidate biomarkers were identified and validated.

Ectopic right parietal pleural thymic carcinoma: a rare case and review of the literature

Ectopic thymic carcinoma is extremely rare. We present a case of a 73-year-old male patient with ectopic right parietal pleural thymic carcinoma and performed a literature review. Computed tomography (CT) of the chest demonstrated a sharp-edged soft tissue mass with intense enhancement measuring 47 mm × 29 mm with a broader base adjacent to the right axillary chest wall at the level of the 5th rib. There was no hilar or mediastinal lymphadenopathy or evidence of a mediastinal tumor or pleural nodules. A totally extra-pleural tumor resection and partial right lung resection was performed. Histological examination demonstrated infiltrative growth typical of carcinoma cells with a nest-like distribution locally invading the surface of the lung tissue. Immunohistochemical examination confirmed the diagnosis of thymic squamous carcinoma positive for CD5. Mediastinal radical radiotherapy (60 Gy) was performed postoperatively. The patient was followed for 17 months without any evidence of recurrence or metastasis.

Clinical value of contrast-enhanced ultrasound in improving diagnostic accuracy rate of transthoracic biopsy of anterior-medial mediastinal lesions

OBJECTIVE

To evaluate the clinical value of contrast-enhanced ultrasound (CEUS) in transthoracic biopsy of anterior-medial mediastinal lesions.

METHODS

A total of 123 patients with anterior or middle mediastinum lesions required ultrasound guided transthoracic biopsy for pathological diagnosis. Among them, 72 patients received CEUS examinations before biopsy. After CEUS, 8 patients were excluded from biopsy and the rest 64 patients underwent biopsy (CEUS group). During the same period, 51 patients received biopsy without CEUS examination (US group). The ultrasonography characteristics, the number of biopsy puncture attempts, diagnostic accuracy rate and the incidence of complications were recorded and compared between the two groups.

RESULTS

A large portion of necrosis area or superficial large vessels was found in 8 patients, so the biopsy was cancelled. The internal necrosis was demonstrated in 43.8% of the lesions in CEUS group and in 11.8% of US group (P>0.001). For thymic carcinoma, CEUS increased the detection rate of internal necrosis and pericardial effusion than conventional ultrasound (62.5% vs. 18.8%, P=0.012; 56.3% vs. 12.5%, P=0.023). The average number of punctures in CEUS group and US group was 2.36±0.70 and 2.21±0.51 times, respectively (P>0.05). The diagnostic accuracy rate of biopsy in CEUS group (96.9%, 62/64) was significantly higher than that in US group (84.3%, 43/51) (P=0.022). In US group, 2 patients suffered from mediastinal bleeding (3.9%), while no major complications occurred in CEUS group.

CONCLUSIONS

CEUS examination provided important information before transthoracic mediastinum biopsy and improved diagnostic accuracy rate in biopsy of anterior and middle mediastinum lesions than conventional ultrasound.