Lung Carcinoma: Issues and Challenges

23 Jun 2022 09:00 09:30
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Controversies and challenges in the diagnosis of lung carcinoma according to the 2021 WHO “Blue Book”

 

Angela Takano1,2

1Singapore General Hospital, Singapore; 2National University Singapore, Singapore

 

A new histologic classification of lung adenocarcinoma subtypes with prognostic significance was published in the 2015. It was later recognized, that the subtypes had some subtleties which modified the prognosis. These and a new grading system were published in the 2021 edition. Variants of lung adenocarcinoma such as invasive mucinous adenocarcinoma and enteric were recognized again.  Invasive mucinous adenocarcinomas have to be differentiated from non-variant adenocarcinomas that produce abundant mucin. The presence of multiple tumours poses a special challenge: to determine if the tumour is a separate primary or a metastasis from the larger primary. This may or not be possible by examination of the histologic characteristics, however, it is an important issue because it may change the stage depending on the size of the larger tumour and the location of the separate, smaller tumour. Finally, pathologic examination of specimens post-neoadjuvant therapy poses several challenges: It may be necessary to process the whole tumour bed area in order to be able to determine the true effect of neoadjuvant therapy, which may not be possible in all practice settings. The recognition of post-neoadjuvant effect on tumour cells is challenging.  The calculation of the proportions of viable tumour, stroma and necrosis is performed rather heuristically, since the determination of volumes of tumour, necrosis and stroma described as percentages of the total volume of a previously existing tumour bed would actually require some form of calculus in order to be precise.