Tumor location may affect the clinicopathological features and prognosis of thymomas

Thymoma: An Overview

Thymomas are considered one of the most prevalent types of mediastinal epithelial tumors, which frequently develop in the anterior mediastinum. Due to their rarity, these tumors' nomenclature, classification, and staging are likely to be the subject of debate and argument for most expert pathologists. Furthermore, the significance of thymoma histologic classifications have been debated over the past twenty years. While certain advocates argue that staging at the time of diagnosis is more significant, others believe that histologic subtyping has a significant impact on how patients behave clinically. In this review, we will focus on some of the challenges that diagnostic surgical pathologists may experience while evaluating the histopathology of thymomas and staging these tumors. We will additionally glance over the clinical characteristics of these distinct tumors and the current management strategy.

Prognostic factors for overall survival after surgical resection in patients with thymic epithelial tumors: A systematic review and meta-analysis

BACKGROUND

Thymic epithelial tumors (TETs) originate in the thymic epithelial cell, including thymoma and thymic carcinoma. Surgical resection is the first choice for most patients. However, some studies have shown that the factors affecting the prognosis of these patients are not consistent. To evaluate prognostic factors in patients with surgically resected thymic epithelial tumors, we performed a meta-analysis.

METHODS

We searched the Chinese biomedical literature database, Pubmed, Embase, Cochrane Library and other electronic databases. Studies including postoperative overall survival (OS) and predictors of TETs were included. We made a comprehensive analysis the hazard ratios (HRs) through a single proportional combination. HRs were combined using single proportion combinations.

RESULTS

The meta-analysis included 11,695 patients from 26 studies. The pooled OS was 84% at 5 years and 73% at 10 years after TETs operation. The age as continuous-year (HR 1.04, 95% confidence interval (CI) 1.02-1.04), incomplete resection (HR 4.41, 95% CI 3.32-5.85), WHO histologic classification (B2/B3 vs A/AB/B1 HR 2.76, 95% CI 1.25-6.21), Masaoka Stage (stage III/IV vs I/II HR 2.74, 95% CI 2.12-3.55,) were the poor prognostic factors.

CONCLUSIONS

For patients with TETs after surgical resection, advanced age, incomplete resection, WHO classification B2/B3, and higher Masaoka stage are risk factors for poor prognosis.

Thymectomy in ocular myasthenia gravis-prognosis and risk factors analysis

Background

Several retrospective studies have identified risk factors associated with ocular myasthenia gravis (OMG) generalization in non-surgical patients. However, the outcomes of OMG after thymectomy have not been investigated fully. This study aimed to explore the clinical predictors of post-thymectomy OMG prognosis.

Methods

We performed a retrospective review of OMG patients who underwent thymectomy at our institution from January 2012 to December 2021. Kaplan–Meier and Cox proportional hazard regression analyses were used to evaluate associations between clinical features and prognosis. The main outcome measures were OMG conversion, complete stable remission (CSR), and clinical improvement.

Results

Fifty-eight patients were identified for conversion analysis. Thirteen (22.4%) developed generalized myasthenia gravis (GMG) at a median time of 12.7 (3–37.3) months from symptom onset. Repetitive nerve stimulation (RNS)-positivity was associated with increased risk of conversion to GMG (P = 0.002). Patients with histotype B2/B3 thymoma showed a higher risk of conversion (P = 0.002) than did patients with hyperplasia and AB/B1 thymoma. Fifty-two patients fulfilled the criteria for CSR and improvement. Sixteen (30.8%) achieved CSR at a median time of 28.7 (15–54) months after thymectomy. Fifteen (28.8%) showed clinical improvement at last follow up. Patients who achieved CSR showed a younger age of onset (P = 0.022), lower percentage of acetylcholine receptor antibody-seropositivity (P = 0.029). Histologically, patients with thymic hyperplasia and stage I thymoma showed a higher chance of CSR (P = 0.010) than did patients with stage II/III thymoma. Multivariate analysis revealed that RNS-positivity (hazard ratio [HR] 6.007, P = 0.021) and histotype B2/B3 thymoma (HR 4.611, P = 0.048) were associated with OMG conversion. Thymic hyperplasia and stage I thymoma (HR 0.300, P = 0.026) were associated with OMG CSR after thymectomy.

Conclusion

For OMG patients after thymectomy, RNS-positivity and histotype B2/B3 thymoma are independent predictors of conversion to GMG. On the other hand, thymic hyperplasia and stage I thymoma independently predict CSR.

Prognostic Impact of Number of Organ Invasions in Patients with Surgically Resected Thymoma

PURPOSE

This study aimed to explore the clinical implications and prognostic value of the number of organ/structure invasions (NOI) in patients with thymoma after curative surgical resection.

METHODS

We retrospectively analyzed 306 consecutive Japanese patients with thymoma who underwent curative surgical resection. Tumor invasions of pericardium, mediastinal pleura, phrenic nerve, lung, and venous structures were examined histopathologically. Cases were classified into four subgroups according to NOI: group 0, no tumor invasion; group 1, tumor invasion into single organ/structure; group 2, tumor invasion of two organs/structures; group 3, invasion of three or more organs/structures. Associations with NOI and several clinical characteristics and their prognostic significance were analyzed.

RESULTS

Pleural invasion was found in 100 cases (32.7%), lung invasion in 48 cases (15.7%), pericardial invasion in 46 cases (15%), phrenic nerve invasion in 29 (9.5%), and venous invasion in 22 cases (7.2%). NOI was classed as group 0 in 201 cases (65.0%), group 1 in 42 cases (13.7%), group 2 in 20 cases (6.5%), and group 3 in 43 cases (14.1%). Cases with higher NOI showed significantly worse relapse-free survival (RFS) and overall survival (OS). Cox's proportional hazard model analysis also identified NOI as a prognostic factor affecting RFS and OS.

CONCLUSIONS

Cases with higher NOI of thymoma after radical surgical resection showed significantly worse recurrence rates and survival.

Pathological tumor long-to-short axis ratio as a prognostic factor in patients with thymic epithelial tumors

Background

Thymic epithelial tumors (TETs) exhibit irregular shapes reflective of the heterogeneity in tumor growth and invasive properties. We aimed to identify the prognostic value of the pathological tumor long‐to‐short axis (L/S) ratio in TETs.

Methods

A retrospective study was performed on patients with TETs who underwent extended thymectomy between January 1999 and December 2019 in our institute. Patients were divided into two groups according to the threshold of the L/S ratio. Overall survival (OS) and progression‐free survival (PFS) were evaluated by Kaplan‐Meier analysis. The independent prognostic factors of TETs were identified by multivariate analysis. The performance of prediction models for the above survival outcomes with and without the L/S ratio was evaluated using an integrated time‐dependent area under the curve (iAUC).

Results

Eligible patients were divided into two groups based on higher (n = 42) and lower (n = 94) L/S ratios according to a threshold value of 1.39. A significant difference was found between the two groups only in disease progression (p = 0.001). Poorer survival outcomes were found from Kaplan‐Meier curves in the higher L/S ratio group (p < 0.05). In the multivariable analysis, the L/S ratio showed significant effects on OS and PFS (p < 0.05). The performance of models with the L/S ratio was better than that without the L/S ratio in predicting survival outcomes.

Conclusions

The pathological tumor L/S ratio is an independent prognostic factor for OS and PFS in patients with TETs, and an L/S ratio >1.39 is associated with worse survival outcomes.

Thymoma Staging: An Analysis of the Different Schemas

Over the last years, a number of changes has taken place in the evaluation of thymomas. More recently, the introduction of a TNM staging system in the assessment of thymic epithelial tumors, in general, has been put forward. Important to highlight is that this TNM system is not based on tumor size, and because of that shortcoming, it was in need to borrow most if not all of the information from the experience derived from other schemas that over the years have been tested with larger series of cases. Also important to recognize is that this TNM system is nothing new as previous authors in the past had already attempted to provide a TNM system for thymomas without much success. Therefore, it becomes important that those involved with the staging of thymomas become familiar with previous schemas as the TNM system provides a slight different spin in the T component, while the M component truly represents advance stages of previous schemas. More importantly is to also highlight that despite the specific anatomic structures addressed in the T or M assessment, there is little information in the most important aspect of any staging system-clear definitions of invasion and metastasis and the gross assessment of these tumors to provide an accurate staging. Capsular integrity still remains paramount in such assessment. A critical assessment of TNM system compared with previously proposed staging systems and whether there is a real advancement in applying it is discussed as well as the gross assessment of these tumors to highlight the importance of the staging protocol.