Research from Yu-Chuan Hu and Lang Wu shows that several variables which are largely unreported before, including degree of CT enhancement, risk of aggressiveness, and multiple nodule with fibrous septum could preoperatively help determine the WHO pathological classification of TETs patients, especially for the low risk and high risk subtypes.

In this study, they employed the largest cohort of TETs patients up to date to investigate whether CT diagnostic parameters could identify staging of this cancer. The conventional CT findings can determine tumor size, shape, density, involvement of the capsule and surrounding tissues, all of which are related to the WHO histologic classification and clinical stages of TETs. In their study, a greater average tumor diameter indicates a higher probability that the tumor is malignant. It is very often for thymic carcinoma to have a maximum diameter of larger than 8 cm (49.1%). Low risk thymic tumors (types A, AB) are often round or oval with a clear, smooth margin, complete capsule and homogenous density; on the contrary, high risk subtypes (types B1, B2, B3 and thymic carcinoma) are often irregular in shape or deep lobulated. There is usually a higher rate of invasion by direct extending to adjacent structures including pericardium, large vessels or lung. The lobulation rate is bettheyen 60% and 89% based on previous study. Focusing on common CT manifestation parameters, they detected that size, boundary, capsule, homogeneity, septa, necrotic or cystic change, pleural effusion, lymphadenopathy, and invasion of adjacent tissues demonstrated significant differences among the 6 TETs subtypes, which confirms previous findings. However, there was no significant difference for tumor shape among the different pathological types of TETs (P = 0.206), which is inconsistent with previous studies. The finding that there was no significant difference for calcification among the different pathological types of TETs (P = 0.474) confirms the conclusion from a previous systematic review.

CT enhancement is very often used in TETs diagnosis since it can better reveal the tumor shape and invasion to adjacent tissues, as theyll as demonstrate the blood supply to tumor tissues. For the first time, they demonstrated that significantly different degrees of CT enhancement exist for different TETs WHO classifications. The area under the ROC curve for differentiating low (types A, AB) from high risk subtypes (types B1 B2, B3 and thymic carcinoma) reaches 80%. And the best cutting point for CE_max is at 25.5 HU, when the sensitivity and specificity of determining low risk subtypes are 78.8% and 68.5%, respectively. Generally speaking, degree of CT enhancement may represent levels of blood supply, thus should increase with more advanced tumor stages. Research has indicated a significant correlation bettheyen tumor angiogenesis and invasiveness in patients with TETs. However, their finding is out of expectation in suggesting that low risk subtype of thymoma (type A and AB) demonstrated a high degree of CT enhancement while high risk ones demonstrated a much lotheyr degree of CT enhancement. Pan et al studied the clinicopathologic characteristics of spindle cell thymoma (medullary, WHO type A) and mixed spindle/lymphocytic thymoma (WHO type AB), and found that the short-spindled pattern of type A thymoma may commonly arrange in a hemangiopericytic or microcystic pattern, which may explain why a higher degree of CT enhancement exist in low risk subtypes in their study. To the best of their knowledge, this exploration of degree of CT enhancement and stage of TETs has never been investigated before, and focusing on their clinical question itself, this interesting finding implies that degree of CT enhancement can probably predict the classifications of TETs.

The Masaoka staging system has been widely used in the clinical management of TETs with the clinical stage remaining the most important prognostic factor of thymoma. A recent study demonstrated a close relationship bettheyen preoperative CT thymoma staging and postoperative Masaoka clinical staging. Based on CT demonstrations of pathological classifications and Masaoka stages of primary mediastinal tumor, they proposed a parameter of aggressive risk. In this comprehensive analysis of 216 TETs patients, they detected a strong correlation bettheyen CT grade of aggressive risk and WHO histological classification (r = 0.801, P < 0.001). Their data also suggested that such a parameter could potentially help differentiate low from high risk TET subtypes, which could potentially add confidence in such a determination besides the parameter of degree of CT enhancement.

Interestingly, in their study they detected that multiple nodule with fibrous septum appeared in over 77% of type AB thymomas, but was rare in other subtypes and if existed, with a different manifestation. Histologically, type AB thymoma shotheyd multiple nodules separated by fibrous bands. The multiple nodules with fibrous septum features on CT imaging are consistent with the macroscopic appearance of a type AB thymoma (Fig 1). However, high risk TET subtypes especially thymic carcinoma appear as mainly deep lobulation or spiculate protuberance without tumor septum (Fig 1). This finding is useful in determining type AB thymomas. The detection of tumor septum can potentially be useful as a marker for type AB thymoma.

Their study also has limitations to acknowledge. Firstly, they did not analyze CT characteristics of thymic carcinoma according to their specific pathological classifications. Certain subtypes of thymic carcinoma such as neuroendocrine carcinomas have differentiated CT manifestations and prognosis, which warrants further study. Secondly, the complete survival data of these patients are not available, which intimidates the possibility to determine the relationship bettheyen survival and variables of risk of aggressiveness and degree of CT enhancement. The fact that survival rates of TETs patients, especially for those in low risk subgroups, are relatively high and a very long follow up will be required to collect these data. Further study for elucidating this research question is warranted. Thirdly, the hemodynamic analysis of TETs based on histopathology was not conducted, and further study for resolving this research question will be needed to clarify the mechanism of CT enhancement finding in this study.

In conclusion, using the largest sample up to date, they identified that several variables which are largely unreported before, including degree of CT enhancement, risk of aggressiveness, and multiple nodule with fibrous septum could preoperatively help determine the WHO pathological classification of TETs patients, especially for the low risk and high risk subtypes. A combined prediction using these variables will provide a better guidance for appropriate therapeutic strategies for TETs patients.