Thymectomy or partial thymectomy, that is the question: surgical considerations for early-stage thymic epithelial tumors: a narrative review

Introduction

Thymic epithelial tumors (TETs) are relatively rare but clinically significant malignancies, relevant not only to thoracic surgeons but also to oncologists, radiologists, radiation oncologists, and pathologists. Surgical resection remains the cornerstone of treatment, with thymectomy regarded as the standard approach. Guidelines from the National Comprehensive Cancer Network^® (NCCN) (1), the European Society for Medical Oncology (ESMO) (2), and the Japanese Lung Cancer Society (3) all recommend thymectomy. Historically, median sternotomy enabled relatively safe resection for early-stage TETs without invasion of adjacent structures.

Rationale and knowledge gap

Most thymic tumors are thymomas, and the majority of comparative studies between thymectomy and partial thymectomy have focused on this subtype. Short-term outcomes are mixed: some studies report no difference (4,5), while others show lower complication rates or shorter hospitalization following partial thymectomy (6-8). Long-term outcomes, including recurrence and overall survival (OS), are generally comparable, though some reports suggest improved OS with total thymectomy in selected subgroups (5). With minimally invasive techniques such as video-assisted thoracoscopic surgery (VATS) and robot-assisted thoracic surgery (RATS) becoming increasingly popular, it is timely to reassess outcomes of thymectomy versus partial thymectomy.

Objective

This review compares postoperative outcomes of thymectomy and partial thymectomy for early-stage TETs, focusing on short-term outcomes immediately after surgery and long-term outcomes. Since thymectomy is frequently performed in patients with TETs complicated by myasthenia gravis (MG), this review primarily focuses on cases without MG. We present this article in accordance with the Narrative Review reporting checklist (available at https://med.amegroups.com/article/view/10.21037/med-2025-1-47/rc).

Methods

Literature search strategy

A literature search was conducted using the MEDLINE database accessed through PubMed to identify studies comparing thymectomy and partial thymectomy for early-stage TETs. The search included articles published between January 1, 1980 and July 31, 2025. The following keywords and their combinations were used: “thymectomy”, “partial thymectomy”, “thymomectomy”, “thymoma”, and “thymic epithelial tumor”. These terms were searched within titles and abstracts. In addition, the reference lists of relevant original articles and review papers were manually screened to identify potentially eligible studies that were not captured by the initial database search. Only studies published in English were included, considering feasibility and the need for accurate interpretation of surgical techniques and oncological outcomes. Given the heterogeneity of study designs, surgical definitions, and outcome measures, this review was designed as a narrative synthesis rather than a systematic review or meta-analysis. This review primarily focused on early-stage thymoma; studies exclusively addressing thymic carcinoma were not considered the main target of analysis, given the distinct oncologic behavior and surgical principles of this entity. Tumor stage was primarily reported according to the Masaoka or Masaoka-Koga classification, as most included studies predated the widespread adoption of the tumor-node-metastasis (TNM) staging system for TETs. The search strategy is summarized in Table 1.

Study selection and eligibility criteria

Studies were eligible for inclusion if they met all of the following criteria:

• Included patients with early-stage TETs, primarily Masaoka-Koga stage I–II;
• Directly compared thymectomy with partial thymectomy, including thymomectomy or other limited thymic resections preserving residual thymic tissue;
• Reported short-term surgical outcomes, long-term oncological outcomes, or both; and
• Clearly described the extent of surgical resection and outcomes of interest.

Studies focusing exclusively on patients with MG were excluded, as thymectomy is generally indicated in this population irrespective of tumor stage. Case reports, small case series, conference abstracts, non-comparative studies, and studies lacking sufficient outcome data were also excluded.

Given the rarity of TETs and the limited availability of high-quality comparative studies, this review focused on observational cohort studies including at least 30 patients per surgical group or studies employing propensity score-matched analyses.

Titles and abstracts were screened, followed by full-text review of potentially eligible articles. Ultimately, 11 observational cohort studies met the inclusion criteria and were included in the qualitative synthesis.

Definitions of surgical extent

In this review, the extent of surgical resection was defined according to the terminology used in the original studies.

• Thymectomy was defined as complete removal of the thymus gland, including both thymic lobes, regardless of surgical approach.
• Partial thymectomy was used as an umbrella term encompassing procedures in which residual thymic tissue was intentionally preserved. This category included thymomectomy, defined as resection of the tumor with or without a limited margin of surrounding thymic tissue, as well as other forms of limited thymic resection that did not involve complete thymic removal.

Because terminology varied across studies, procedures described as “thymomectomy”, “limited thymectomy”, or “tumor resection” were collectively categorized as partial thymectomy when residual thymic tissue was preserved. Studies in which the extent of resection could not be clearly classified based on the published description were excluded.

Data extraction and synthesis

Due to substantial clinical and methodological heterogeneity across studies, including differences in staging systems, surgical extent, and follow-up duration, a quantitative synthesis was not attempted, and findings were summarized narratively. From each included study, data were extracted regarding study design, geographic region, sample size, tumor stage and histology, definition of partial thymectomy, surgical approach, duration of follow-up, and reported surgical and oncological outcomes.

Given the heterogeneity in tumor stage, histology, surgical approach, and follow-up duration across studies, a quantitative synthesis was not performed. Instead, outcomes were evaluated using a structured narrative approach, with studies grouped by short-term surgical outcomes and long-term oncologic outcomes, and greater interpretative weight assigned to larger, multicenter studies and those employing methods to control for confounding, such as propensity score matching (PSM). The key characteristics and outcomes of the included studies are summarized in an at-a-glance format in Table 2. The process of study identification and selection is illustrated in Figure 1. When conflicting results were observed, interpretation was guided by study size, methodological rigor, and the use of confounding adjustment methods, such as PSM, rather than simple vote counting across studies.

Figure 1 Flow diagram of study selection. A PRISMA-style flow diagram illustrating the study selection process for this narrative review. Records were identified through a MEDLINE (PubMed) search, screened by title and abstract, and assessed by full-text review according to predefined eligibility criteria. Eleven studies were ultimately included in the qualitative synthesis. MG, myasthenia gravis.

Thymectomy or partial thymectomy

Comparison of short-term outcomes of thymectomy and partial thymectomy

Several studies have compared short-term postoperative outcomes between thymectomy and partial thymectomy. Operative time is frequently shorter with partial thymectomy and intraoperative blood loss is often lower (6,8,9). Findings for postoperative hospital stay are mixed: some studies report no significant difference (4,5,9), while others show shorter stays with partial thymectomy (8). Postoperative complications also show vary, with some studies indicating no difference (4,5,9) and others reporting fewer complications in the partial thymectomy group (6,8). The incidence of postoperative MG appears comparable between the two procedures (6,11-13). Postoperative mortality is inherently low, and while comparative data are limited, Guerrera et al. reported no significant difference in 30-day mortality (5). These findings are further supported by two recent meta-analyses (15,16). Taken together, current evidence indicates that short-term postoperative outcomes are at least equivalent between thymectomy and partial thymectomy, with some parameters slightly favoring the partial approach.

Comparison of long-term outcomes of thymectomy and partial thymectomy

Recurrence rate and disease-free survival (DFS)

Previous studies reveal no significant difference in recurrence rates between patients undergoing thymectomy and those undergoing partial thymectomy (6,7,9,12-14). Notably, these studies using PSM to adjust for baseline characteristics also found similar recurrence rates between the two groups (7,9,10,14). Conversely, analyses of the European Society of Thoracic Surgeons (ESTS) database indicated a significantly lower recurrence rate in the thymectomy group, regardless of PSM (5).

Regarding DFS, no significant differences were observed in multivariate analyses (11) or in intergroup comparisons after PSM (4,14). Additionally, meta-analyses by Xu et al. and Papadimas et al. reported equivalent recurrence rates and DFS between the two procedures (15,16). Notably, both meta-analyses were limited to studies of thymoma without MG.

Oncologic considerations beyond extent of resection

Several important oncologic factors warrant consideration when interpreting the results of limited versus complete thymic resection. Margin status has not been uniformly reported across retrospective studies, and the impact of microscopic residual disease on recurrence risk remains unclear. Similarly, systematic lymph node assessment is not routinely performed in thymoma surgery, and available studies provide limited data on nodal evaluation, particularly in the context of partial thymectomy. In addition, patterns of recurrence following limited resection have not been consistently characterized. While local recurrence appears to be the predominant mode of failure in early-stage thymoma, detailed comparisons of locoregional versus distant recurrence according to the extent of resection are scarce. These limitations underscore the need for cautious interpretation of oncologic equivalence and highlight areas requiring further investigation.

OS

Most reports indicate no significant difference in OS between thymectomy and partial thymectomy (4,7,11-13), including two studies that used PSM to adjust for baseline characteristics (4,7). Narm et al. conducted a multicenter study using a Korean database, comparing 141 patients in each group after PSM adjustment (8). These studies indicated that OS was initially higher in the thymectomy group, but the extent of resection was not a significant factor in multivariate analysis.

Gu et al. performed a multicenter study in China, including 796 thymectomy and 251 partial thymectomy cases with Masaoka-Koga stage I–II TETs (13). Overall OS did not differ significantly, although a subset analysis of Masaoka-Koga stage II patients showed superior OS in the thymectomy group. Regarding the reason for this, we speculate that the proportion of thymic carcinoma and neuroendocrine tumors may have been higher in the thymic partial resection group in their study cohort (the proportion of thymic carcinoma and carcinoid tumors was 6.4% in the thymectomy group and 17.1% in the thymic partial resection group). Guerrera et al.’s ESTS database analysis demonstrated better OS in the thymectomy group before PSM, with a trend toward better OS after PSM (5). Conversely, Xu et al.’s meta-analysis also found comparable OS between the two procedures (15).

Advantages of thymectomy

In tumors classified as Masaoka stage II or higher, which have the potential for tumor invasion beyond the capsule, partial thymectomy carries a risk of residual tumor. Thymic carcinoma and thymic neuroendocrine tumors also have a higher likelihood of metastasizing to regional lymph node compared with thymoma. Thymectomy allows simultaneous resection of these lymph nodes, whereas partial thymectomy may not achieve complete clearance.

Although rare, in cases of multiple thymomas (17), thymectomy is considered more preferred. However, in thymoma, lymph node and distant metastases are uncommon, and local recurrence is more frequent. In such cases, if recurrence occurs, reoperation may be relatively straightforward, particularly when the initial surgery was not performed via a median sternotomy.

Disadvantages of thymectomy

Compared with partial thymectomy, thymectomy is generally associated with longer operative times and greater blood loss (6,8,9). A recent case-control study by Kooshesh et al. highlighted potential long-term risks associated with thymectomy in adults (18). This study compared 1,420 individuals who underwent thymectomy with 6,021 controls and found significantly higher all-cause mortality (relative risk 2.9) and cancer incidence (relative risk 2.0) in the thymectomy group. These findings suggest that thymectomy may negatively affect long-term outcomes, including the development of malignancies, indicating that the thymus may play an important role in both children and adults.

Several epidemiological studies have also reported a higher incidence of secondary cancers in patients following thymic tumor surgery compared with the general population (19-21). Although the mechanisms remain unclear, the findings of Kooshesh et al. (18) raise the possibility that thymectomy itself could contribute. If partial thymectomy and thymectomy show equivalent oncologic efficacy, partial thymectomy—which preserves some thymic tissue—may offer an advantage.

Limitations

This review has several limitations. First, the number of available studies addressing the extent of thymic resection remains limited, and most of the evidence is derived from retrospective observational cohorts. Second, there is no standardized definition or surgical technique for thymectomy or partial thymectomy, resulting in substantial heterogeneity in operative extent, surgical approach, and patient selection across studies. Third, the long-time span over which the included studies were conducted suggests that surgical techniques, perioperative management, pathological classification, and postoperative surveillance strategies have evolved considerably, potentially influencing reported outcomes. In addition, important oncologic considerations beyond the extent of resection are insufficiently and inconsistently reported in the existing literature. Margin status is not uniformly described, and the impact of microscopic residual disease on recurrence risk cannot be reliably assessed. Systematic lymph node evaluation is also not routinely performed in thymoma surgery, and available studies provide limited data on nodal assessment, particularly in the context of partial thymectomy. Furthermore, patterns of recurrence after limited resection, including locoregional versus distant failure, have not been consistently characterized, limiting meaningful comparisons between surgical strategies. In addition, this review did not specifically address surgical approaches or techniques for thymic carcinoma, for which the role of limited resection is fundamentally different from that in thymoma. Although TNM staging is increasingly recognized as an important oncologic framework, most available comparative studies were conducted before its routine implementation, precluding meaningful TNM-based analyses in this review.

Finally, as a narrative review, rather than a systematic review or meta-analysis, this study inherently carries limitations in validity and reproducibility. The literature search was limited to a single database (MEDLINE via PubMed) and restricted to English-language publications, which may have introduced selection and language bias. In addition, study selection was not performed in duplicate, and no formal risk-of-bias assessment was conducted. Therefore, the conclusions should be interpreted with caution and viewed as a synthesis of currently available evidence rather than definitive proof of oncologic equivalence.

Conclusions

This review does not aim to generate new evidence but rather to clarify the current state of knowledge, inconsistencies, and unmet needs regarding the extent of thymic resection in early-stage TETs. Partial thymectomy appears to provide favorable short-term outcomes, including reduced blood loss and lower postoperative complication rates. Also, long-term prognosis over a follow-up period of approximately 5 years appears comparable to that of thymectomy, suggesting that partial thymectomy may be a feasible option in carefully selected patients with early-stage thymoma; however, the available evidence is derived exclusively from retrospective observational studies, and definitive conclusions regarding oncologic equivalence cannot be drawn.

Most studies have utilized a median sternotomy approach, and it remains unclear whether these findings apply in the current era of minimally invasive surgery, including VATS and RATS. Moreover, data beyond 5 years are lacking, and evidence regarding thymic tumors other than thymoma, such as thymic carcinoma, is limited. The rarity of thymic tumors makes it difficult to conduct randomized controlled trials assessing resection margins, as is feasible in non-small cell lung cancer (22,23). Therefore, higher-quality, multicenter collaborative studies are needed. Accumulating contemporary data on minimally invasive approaches will be essential to clarify the relative advantages and limitations of thymectomy versus partial thymectomy.

Acknowledgments

We would like to express our gratitude to the editorial board of this journal for commissioning this narrative review.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://med.amegroups.com/article/view/10.21037/med-2025-1-47/rc

Peer Review File: Available at https://med.amegroups.com/article/view/10.21037/med-2025-1-47/prf

Funding: This study was funded by the Japanese Red Cross Aichi Medical Center Nagoya Daiichi Hospital Research Grant (No. NFRCH 25-0007).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-2025-1-47/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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