Staging of thymic epithelial neoplasms: thymoma and thymic carcinoma

Prognostic factors and outcome in cats with thymic epithelial tumours: 64 cases (1999-2021)

OBJECTIVES

To describe the clinical presentation, treatment and outcomes of cats diagnosed with thymic epithelial tumours and to determine prognostic factors for survival and recurrence.

MATERIALS AND METHODS

Clinical records of cats diagnosed with a thymic epithelial tumour between 1999 and 2021 at three referral institutions were retrospectively reviewed.

RESULTS

Sixty-four cats were included. Paraneoplastic syndromes were present in nine cats and metastatic disease was seen in two cats, one at diagnosis and one at the time of recurrence. Median tumour diameter was 6 cm (range, 2 to 15) and a cystic appearance was described on imaging in 25 cats. Surgical excision was attempted in 54 cats with a perioperative mortality rate of 11%. Median survival time for cats surviving to hospital discharge was 897 days (range, 21 to 3322). The 1-, 2- and 5-year survival rates for surgically treated thymic epithelial tumour were 86%, 70% and 66%, respectively. Survival was longer for cats with Masaoka-Koga stage I and II tumours compared to stages III and IV (1366 days versus 454 days; P=0.002). Masaoka-Koga stage was the only significant prognostic factor detected on multi-variable analysis, with stage III and IV tumours associated with increased risk of death (hazard ratio: 5.67, 95% confidence interval: 1.29 to 24.91, P=.021). Tumour recurrence occurred in 11 cats at a median of 564 days (range, 93 to 1095); no significant prognostic factors for recurrence were identified.

CLINICAL SIGNIFICANCE

Cats with thymic epithelial tumours had a good long-term prognosis following surgery. Tumour recurrence can occur late in the disease course and ongoing monitoring should therefore be considered. Masaoka-Koga stage may influence survival time and could be used to predict outcome.

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.

Comparison of Interobserver Agreement and Diagnostic Accuracy for IASLC/ITMIG Thymic Epithelial Tumor Staging Among Co-registered FDG-PET/MRI, Whole-body MRI, Integrated FDG-PET/CT, and Conventional Imaging Examination with and without Contrast Media Administrations

RATIONALE AND OBJECTIVES

The purpose of this study was to compare the interobserver agreements and diagnostic accuracies for IASLC/ITMIG (International Association for the Study of Lung Cancer/International Thymic Malignancies Interest Group) thymic epithelial tumor staging of co-registered fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (FDG-PET/MRI), MRI, integrated fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), and conventional imaging examination.

MATERIALS AND METHODS

Prospective whole-body MRI including diffusion-weighted imaging, integrated PET/CTs, conventional imaging examinations, pathological examinations, and surgical reports, as well as follow-up examinations, were performed for 64 consecutive patients with thymic epithelial tumor. All FDG-PET/MRIs were co-registered PET data with MRI. TNM staging was evaluated by two radiologists on the basis of the IASLC/ITMIG thymic epithelial tumor staging system. Kappa statistics were determined for evaluations of agreements of all factors between each of the methods and final diagnosis. Finally, the diagnostic accuracy of each factor and of determination of the clinical stage was statistically compared to each other using McNemar test.

RESULTS

Agreements for all factors between each method and final diagnosis were assessed as fair, moderate, substantial, or almost perfect (0.28 ≤ kappa value ≤ 0.80; P < .0001). Diagnostic accuracy for N factor of PET/MRI (93.8% [60/64]) and MRI (93.8% [60/64]) was significantly higher than that of conventional imaging examination (81.3% [52/64] vs PET/MRI and MRI; P = .008). In addition, diagnostic accuracy for staging of PET/MRI (84.4% [54/64]) and MRI (84.4 [54/64]) was significantly higher than that of conventional imaging examination (71.9% [46/64] vs PET/MRI and MRI; P = .008).

CONCLUSIONS

Whole-body PET/MRI, MRI, and PET/CT have better interobserver agreements and accuracies than conventional imaging examination for the new IASLC/ITMIG thymic epithelial tumor staging.

Predicting Masaoka-Koga Clinical Stage of Thymic Epithelial Tumors Using Preoperative Spectral Computed Tomography Imaging

Objectives

To investigate the utility of spectral computed tomography (CT) parameters for the prediction of the preoperative Masaoka-Koga stage of thymic epithelial tumors (TETs).

Materials and Methods

Fifty-four patients with TETs, aged from 37 to 73 years old, an average age of 55.56 ± 9.79 years, were included in the study.According to the Masaoka-Koga staging method, there were 19 cases of stage I, 15 cases of stage II, 8 cases of stage III, and 12 cases of stage IV disease. All patients underwent dual-phase enhanced energy spectral CT scans. Regions of interest (ROIs) were defined in sections of the lesion with homogeneous density, the thoracic aorta at the same level as the lesion, the outer fat layer of the lesion, and the anterior chest wall fat layer. The single-energy CT value at 40-140 keV, iodine concentration, and energy spectrum curve of all lesion and thoracic aorta were obtained. The energy spectrum CT parameters of the lesions, extracapsular fat of the lesions, and anterior chest wall fat in stage I and stage II were obtained. The energy spectrum CT parameters of the lesions, enlarged lymph nodes and intravascular emboli in the 3 groups were obtained. The slope of the energy spectrum curve and the normalized iodine concentration were calculated.

Results

In stage I lesions, there was a statistically significant difference between the slope of the energy spectrum curve for the lesion and those of the fat outside the lesion and the anterior chest wall in the arteriovenous phase (P<0.001, P<0.001). The energy spectrum curve of the tumor parenchyma was the opposite of that of the extracapsular fat. In stage II lesions, there was a statistically significant difference between the slope of the energy spectrum curve for the anterior chest wall and those of the lesion and the fat outside the lesion in the arteriovenous phase(P<0.001, P<0.001). The energy spectrum curve of the tumor parenchyma was consistent with that of the extracapsular fat. Distinction between stage I and II tumors be evaluated by comparing the energy spectrum curves of the mass and the extracapsular fat of the mass. The accuracy rate of is 79.4%. For stages III and IV, there was no significant difference in the slope of the energy spectrum curve of the tumor parenchyma, metastatic lymph node, and intravascular embolism (P>0.05). The energy spectrum curve of the tumor parenchyma was consistent with that of the enlarged lymph nodes and intravascular emboli. The two radiologists have strong consistency in evaluating TETs Masaoka-Koga staging, The Kappa coefficient is 0.873,(95%CI:0.768-0.978).

Conclusion

Spectral CT parameters, especially the energy spectrum curve and slope, are valuable for preoperative TET and can be used in preoperative staging prediction.

The role of targeted therapy in thymic carcinoma

Thymic carcinoma is a rare entity and can be distinguished from benign thymomas by their aggressive nature and poor prognosis. The National Comprehensive Cancer Network guidelines recommend resection followed by adjuvant platinum-based chemotherapy for resectable tumors. However, the outcomes for metastatic or relapsed thymic carcinomas are poor with no regimen showing a consistent benefit. Moreover, the relative rarity of these tumors makes clinical trials difficult. Molecular analysis of thymomas shows a high incidence of genetic mutations and targeted therapy holds promise. We will briefly outline and review the current role of targeted therapy in thymic cancer.

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.

Elevated pretreatment serum lactate dehydrogenase level predicts inferior overall survival and disease-free survival after resection of thymic carcinoma

Background

The prognostic significance of serum lactate dehydrogenase (LDH) level in thymic carcinoma (TC) remains unclear. Therefore, we evaluated the role of pretreatment serum LDH level in the prognosis for TC in this study.

Methods

Sixty consecutive surgical patients were analyzed in this study with pathologic confirmed TC in Sun Yat-sen University Cancer Center from June 1996 to June 2014.

Results

The cut-off value of LDH was 210.50 IU/L. In both univariate analysis and multivariable analysis, only pretreatment serum LDH level (P=0.027) and pathological Masaoka stage (P=0.041) were associated with overall survival (OS). In univariate analysis, pretreatment serum LDH level, tumor size, postoperative radiotherapy (PORT) and pathological Masaoka stage were associated with disease-free survival (DFS) (all P<0.050). Multivariable analysis showed that LDH level (P=0.001), PORT (P=0.001) and pathological Masaoka stage (P=0.038) were independently prognostic factors of DFS. This study also revealed that male patients and larger tumor size had a significantly higher rate of elevated pretreatment serum LDH level than in the other groups.

Conclusions

In conclusion, pretreatment serum LDH level was an independent prognosis factor of OS and DFS for patients with TC.

Metastatic thymoma involving the bone marrow

Although relatively rare, thymomas can be involved in a considerable variety of clinical presentations. Clinicians should be mindful of the breadth of associations with other diseases, including autoimmune disorders and many secondary nonthymic malignancies. For the pathologist, knowledge of the extremely varied histopathologic presentation of thymoma is vital to formulate a proper differential, workup, and diagnosis. The presented case illustrates the finding of very rare metastatic thymoma involvement of bone marrow, identified during evaluation for pancytopenia. The history of prior prostate cancer and an uncharacterized pancreatic lesion, as well as the familial presentation, also suggests a possible underlying hereditary syndrome.