Masaoka-Koga and TNM Staging System in Thymic Epithelial Tumors: Prognostic Comparison and the Role of the Number of Involved Structures

Simple Summary

Thymic epithelial tumors were originally staged using the Masaoka–Koga staging system, even if recently the adoption of the tumor node metastases staging system was recommended. However, it remains controversial as to which staging system is the most effective in prognosis prediction for these patients. The aim of this study was to analyze the prognostic effectiveness of these staging systems and to verify a possible improvement.

Abstract

Background: The aim of this study was to evaluate the Masaoka–Koga and the tumor node metastases (TNM) staging system in thymic epithelial tumors (TET) considering possible improvements. Methods: We reviewed the data of 379 patients who underwent surgical resection for TET from 1 January 1985 to 1 January 2018, collecting and classifying the pathological report according to the Masaoka–Koga and the TMN system. The number of involved organs was also considered as a possible prognostic factor and integrated in the two staging systems to verify its impact. Results: Considering the Masaoka–Koga system, 5- and 10-year overall survival (5–10YOS) was 96.4% and 88.9% in stage I, 95% and 89.5% in stage II and 85.4% and 72.8% in stage III (p = 0.01), with overlapping in stage I and stage II curves. Considering the TNM system, 5–10YOS was 95.5% and 88.8% in T1, 84.8% and 70.7% in T2 and 88% and 76.3% in T3 (p = 0.02), with overlapping T2–T3 curves. Including the number of involved structures, in Masaoka–Koga stage III, patients with singular involved organs had a 100% and 76.6% vs. 87.7% 5–10YOS, which was 76.6% in patients with multiple organ infiltration. Considering the TNM, T3 patients with singular involved structures presented a 5–10YOS of 100% vs. 62.5% and 37.5% in patients with multiple organ involvement (p = 0.07). Conclusion: The two staging systems present limitations due to overlapping curves in early Masaoka–Koga stages and in advanced T stages for TNM. The addition of the number of involved organs seems to be a promising factor for the prognosis stratification in these patients.

Radiological features and metastatic patterns of thymic neuroendocrine tumours

AIM

To investigate the clinical and image features of thymic neuroendocrine tumours (NETs), and characterise the radiological patterns of recurrence and metastasis on serial imaging studies.

MATERIALS AND METHODS

The study included 14 patients (11 males) with a histopathological diagnosis of thymic NETs (one typical carcinoid, eight atypical carcinoid, and five large cell neuroendocrine carcinoma). Preoperative images were assessed for features of primary tumours. Follow-up imaging studies were evaluated for the patterns of metastasis or recurrence.

RESULTS

Underlying endocrine or autoimmune disorders were present in four patients (29%), including multiple endocrine neoplasia (MEN) type 1 (n=3) and autoimmune thyroiditis (n=1). On preoperative imaging, the primary tumours were commonly lobulate and heterogeneous, infiltrated the surrounding fat, and showed ≥50% abutment of the mediastinal structures, with the mean longest diameter of 14 cm (range: 4.1-28 cm). No significant differences of preoperative imaging features were noted among histopathological subtypes. Metastasis or recurrence was noted in 11 of the 14 patients (79%). Ten patients developed intrathoracic metastasis or recurrence, involving thoracic lymph nodes (n=7), pleura (n=4), lung (n=4), pericardium (n=4), and local recurrence in the postoperative mediastinum (n=3). Eight of the 11 patients also had extra-thoracic metastasis, involving bone (n=6), abdominal lymph nodes (n=4), liver, pancreas, kidney, adrenal gland, spleen and brain (n=1 for each site).

CONCLUSIONS

Thymic NETs presented as a large, lobulate, heterogeneous mass with an infiltrative nature. Metastasis and recurrence were frequent, most commonly involving thoracic lymph nodes, while extra-thoracic metastasis to bones and abdominal lymph nodes were also noted.

Neuroendocrine tumors of the thymus and mediastinum

Neuroendocrine tumors of the thymus (tNET) and mediastinum are very rare neoplasms with scarce available data. All subtypes [typical and atypical carcinoid tumors (TC and AC), large cell neuroendocrine and small cell carcinoma (SCC)] observed elsewhere in the body occur also in the mediastinum and show only few if any organ-specific morphological differences. Although all available data suggest that the broad principles that govern the biology (and hence) the classification of these tumors in general apply also to tNET, there are a few noteworthy peculiarities related e.g., to risk factors, relative frequency and also to molecular genetic features. In this review, we will briefly summarize current knowledge on tNET with a special emphasis on shared and private features in comparison e.g., with pulmonary NET, which have traditionally been regarded the next closely related NET group.