Thymomas: a continuing challenge.

Thymic epithelial tumors usually are broadly classified into two main categories: thymoma and thymic carcinoma. In adults, thymomas are the most common primary tumor in the anterior mediastinum.[2] A large variety of paraneoplastic or parathymic syndromes may suggest the presence of a thymoma.[3] Myasthenia gravis coexists in approximately 30% to 40% of patients with thymoma.[4] It is still unclear whether thymoma causes myasthenia gravis or vice versa. The definition, diagnosis, and treatment of thymomas have been periodically re-evaluated. Controversies persist regarding histological classification, staging, surgical approach, and adjuvant and neoadjuvant therapy. In the foregoing article, Drs. Kalhor and Moran discuss still-unresolved issues in these uncommon tumors. First among these is the issue of histologic classification, which has always attracted the interest of pathologists. Controversies and confusion regarding the “traditional”[5] and “histogenetic”[6] proposed classifications persist, and both schemas remain open to challenge. However, despite the fact that certain histologies seem to correlate with certain outcomes, independent of surgical staging, multivariate analysis has almost invariably demonstrated that histology is not of independent prognostic value.[7] We consider correct the authors’ statement about tumor sampling, which is often neglected.[8] Thymomas display different growth patterns; thus, at least five sections of the specimen are necessary to achieve a more reliable classification.[9] Staging represents a crucial prognosticator, and its definition is a challenge. Several staging systems have been proposed since the first was introduced by Berg in 1978.[10] The developer of this system proposed that a proper stratification of patients was advantageous both for predicting prognosis and for choosing the best therapies. The staging system proposed by Masaoka in 1981[11] has been the most successful. Its greatest limitation is the fact that it assigns a fundamental role to macroscopic findings, which are easily detectable by the surgeon during the operation, but not by the pathologist, to whom it falls to determine the answer to the basic question of whether or not the tumor is encapsulated. As thoracic surgeons, we for the most part appreciated the recent analysis by Moran et al,[7] which proposed a staging system whose aim was not only to facilitate the work of pathologists, surgeons, and other clinicians, but also to offer key information for the stratification of patients, with the ultimate goal of more appropriate medical therapy. We hypothesize that additional elements for an optimal staging system can be derived via molecular techniques.[12] At present, however, we can affirm that pathological staging seems to be the single most relevant factor in prognosis, together with the completeness of the resection. We agree with the authors when they state that treatment of thymomas is primarily surgical. To date surgery through a total sternotomy appears irreplaceable and is used as part of a multimodality strategy. In experienced hands, complete surgical resection is easy to perform in encapsulated or limited invasive tumors. It assures the best chance for cure in approximately 90% of patients with localized tumors. Extended operations can be successfully carried out that include the lung, innominate vein, superior vena cava, aortic arch, main pulmonary artery, and chest wall.[13] Recently, minimally invasive approaches have been used for early-stage thymomas. This modality is safe and feasible, with a shorter hospital stay and better patient acceptance. However, additional