Abstract
The biggest change in the 8th edition of the tumor, lymph node, and metastasis (TNM) classification is the recommendation of the solid component diameter and invasive size for determining the clinical and pathological T-factor, respectively. Here, we validated new proposals for the Lung Cancer TNM classification’s revision and compared clinical and pathological T-stages. We retrospectively analyzed 177 cases of non-small cell lung cancers without lymph node metastasis, and involving complete resection, that occurred in our department between January 2017 and March 2019. We reviewed the overall tumor diameter, solid component diameter, and clinical T-factor on computed tomography (CT), and the pathological tumor diameter, pathological invasion diameter, pathological T-factor, and prognosis. The difference between the pathological invasive size and solid size on CT was within 5 mm in 99 cases (56%). At a two-year recurrence-free survival rate, the clinical T-stage demonstrated a better prognostic outcome than the pathological T-stage. Despite including the benign findings, the solid component diameter was better correlated with prognosis than the invasive size. Therefore, in cases of discrepancies of clinically and pathologically detected tumor size, the solid CT size should also be used for the pathological T classification.
Highlights
T-descriptors were announced by the International Association for the Study of Lung Cancer (IASLC) in the tumor, node, and metastasis (TNM) classification’s 8th edition for lung cancer in 2015 [1].The biggest change in this edition is the recommendation of the solid and the invasive component diameter for determining the clinical and pathological T-factor, respectively
The measurement of the pathological invasion diameter differs among pathologists who specialize in lung cancer
Travis et al provided a list of key questions to guide future research in assessing tumor size by TNM classification in lung adenocarcinomas presenting with subsolid nodules by computed tomography (CT) or with a lepidic component by pathologic examination. We have considered this list of key questions and in particular the following from a practical perspective: “What is the reproducibility of measuring size in invasive versus lepidic components, and how can this be improved [2]?”
Summary
The biggest change in this edition is the recommendation of the solid and the invasive component diameter for determining the clinical and pathological T-factor, respectively. For part-solid tumors, the invasive component’s size is used to assign the T category [2]. The invasion size was incorporated into lung cancer’s T-factor classification from a literature search without any large-scale investigation [2]. There have been disagreements among pathologists regarding the diagnosis of lung adenocarcinoma subtypes [3]. When lung adenocarcinoma diagnoses individually reviewed by two lung pathologists are compared, the diagnostic concordance is only 82.4% [4]. The measurement of the pathological invasion diameter differs among pathologists who specialize in lung cancer.
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