Can microct be used to differantiate solid patterned LUNG tumors?

Aim: Lung cancer is a common and fatal cancer. As in other human tumors, microscopic examination is the gold standard for diagnosis of lung tumors. Common pulmonary tumors show various patterns, and there is a group of tumors showing solid organization. These include solid adenocarcinomas (SAc), squamous cell carcinomas (SqCC), and carcinoid tumors (CT). Micro computed tomography (microCT) is a tomographic method using X-rays. It has a working principle similar to conventional computed tomography; however, the voxel size of microCT varies between 1-50 micrometers. This gives the opportunity to reach a much more precise resolution than that can be obtained via conventional computed tomographies. It is possible to obtain images similar to histopathological images with microCT. In the current study, it was aimed to analyze whether different lung tumors with solid pattern can be differentiated from each other with microCT, and to investigate the differentiation of tumoral and non-tumoral lung tissue. Materials and methods: In this study, whole slide hematoxylin and eosin stained images (WSI) of three types of pulmonary tumors (5 SAc, 5 SqCC, 5 CT) were obtained using 3D HISTECH, Panoramic P250 Flash 3, Version Panoramic Scanner 3.0.2. scanner. MicroCT images were obtained from paraffin blocks of these tumors with Bruker Skyscan 1275, (Kontich, Belgium). These microCT images were examined by comparing them with WSIs, and the selected representative regions of interests (ROIs) on WSIs were transferred to the obtained microCT images. Structural parameters (percent object volume, structure thickness, intersection surface, structure linear density, connectivity, connectivity density, open porosity, closed porosity, structure model index) were calculated using the obtained volumes of interest (VOIs) and through these data, the differentiation of tumor types, and tumoral and non-tumoral areas was examined. Kruskal Wallis test, Mann-Whitney U test, cluster analysis, Cohen's kappa, receiver operating characteristic (ROC) curve, sensitivity, specifity, "univariate" logistic regression analysis, Spearman's rho correlation coefficient analyzes were performed using IBM SPSS Statistics for Windows 23. P<0.05 was considered statistically significant. Results: It was found that distinction of tumoral and non-tumoral VOIs at the paraffin blocks can be safely done by all structural parameters (all p values = 0.00). In addition, SAc was found to differ from CT, in terms of "percent object volume" (p=0.011). In addition, in this 4 study, the relationships between the structural microCT parameters and their histological counterparts were revealed. Conclusions: The current study is the first in the literature to investigate the differentiation of solid-patterned lung tumors from each other by microCT. With this study, information on the use and possible benefits of this method in the diagnosis of pulmonary tumors has been obtained. While this method can be used as an auxiliary method for routine histopathological examination in its current form, it can be speculated that it has the potential to replace histopathological examination in some areas, in the future, with its ability to perform a three-dimensional examination without disturbing the tissue integrity. The experience and knowledge of histopathologists on microanatomy of normal and lesional tissues must be used in understanding the possible benefits of this novel technique. Key Words: histopathology, micro computed tomography, paraffin block, pulmonary carcinoma, structural parameters