Which Way is Up? Policies and Procedures for Surgeons and Pathologists Regarding Resection Specimens of Thymic Malignancy

Abstract

T hymic malignancies are relatively uncommon, which mandates that the experience from many different institutions be combined to achieve a better understanding of the disease. Nevertheless, this is hampered by many ambiguities in how results are reported and interpreted. This problem is aggravated by the fact that smaller institutions often encounter these tumors only sporadically. A prerequisite to interinstitutional collaboration is a common language and consistency in the definition of findings (e.g., whether a complete resection was accomplished or not).This article summarizes the policies adopted by the International Thymic Malignancy Interest Group (ITMIG) regarding handling of a resection specimen by the surgeon and pathologist and reporting of the surgical and pathologic findings. These policies are based as much as possible on reported evidence, but this is lacking or limited in many areas. Nevertheless, adoption of a consistent approach is crucial to conduct valid studies moving forward that can clarify areas of uncertainty.This publication addresses only how to handle and process the tissue specimen at the time of a resection. It does not address handling and interpretation of biopsies or cytologic specimens, which is an important topic that is addressed in a separate publication. 1 This article is limited to an open resection (by sternotomy). Although other approaches are sometimes used (e.g., thoracoscopy), the issues involved are also covered in another publication. 2 Furthermore, this article is written with the assumption that resection of a thymoma involves a complete thymectomy along with any adjacent structures that may be involved and that the goal is a complete (R0) resection (i.e., not debulking). METHODSThe process used in development of this document was designed to represent both underlying evidence and a broad consensus of ITMIG members. An initial workgroup consisting of pathologists and surgeons

Thymic epithelial tumours: from basic principles to individualised treatment strategies

“…The incidence of lymph node metastases is largely undetermined in thymic epithelial tumours, as it is unclear in the reported literature how often nodes are biopsied or examined [31]. In the landmark Japanese series of 1,320 resected thymic tumours, lymph node invasion was mostly located in the anterior mediastinum, and was found in 2% of thymomas, including ,1% of stage I cases, and 6% of stage III cases [6].…”

“…Routine removal of anterior mediastinal nodes is recommended for stage III-IV thymomas; in this situation, a systematic sampling of intrathoracic sites is encouraged (i.e. paratracheal, aortopulmonary window and subcarinal areas depending on tumour location) [31]. An even more extensive nodal dissection, including anterior mediastinal, intrathoracic, supraclavicular and lower cervical areas, may be discussed in thymic carcinoma.…”

“…Recent recommendations to facilitate the surgical pathology diagnosis of thymic epithelial tumours were recently made by ITMIG [31]. Communication between surgeons and pathologists is crucial at this step.…”

“…As a standard, the surgical management of thymic epithelial tumours requires the wide opening of the mediastinum and both pleural cavities, which is classically achieved by median sternotomy [2,31,32]. Generally, complete thymectomy, including the tumour, the residual thymus and perithymic fat, is preferred because local recurrences have been observed after partial thymectomy.…”

“…Phrenic preservation may be balanced with complete resection in patients with severe myasthenia gravis. Frozen sections to assess tumour involvement of resection margins are not recommended, given the high risk of false negative results [31].…”