case_images: PMC11813758_01
case_images: High-resolution computed tomography. CT image of the patient with subsolid nodule changes during 4 years. Initial CT image shows a subsolid nodule in the right lower lobe subpleural areas measured approximately 4 mm, with a round shape, smooth margin and clear tumor-lung interface (A, red arrow). CT imaging data from physical examination from 2018 to 2020 (B-D, red arrow).
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case_images: The CT scans showed the gradual appearance of a marginal burr sign and central solid component over time ( Figures 1A-D , red arrow).
case_images: Hematoxylin and eosin staining of the whole tumor. The section shows the double-layered epithelial structure was seen to continue into tall columnar mucinous epithelium (A, 100x and B, 200x). The boundary of the nodule was unclear, with the papillary structure showing a skip growth pattern (red arrows; C, 200x). A continuous basal cell layer and a bilayered structure composed of ciliated cells (red arrow) or mucous cells (yellow arrow) growing along the alveolar wall (D, 200x). Tall columnar mucous cells lack ciliary structures and basal cell layers, with an increased nucleoplasmic ratio (E, 100x and F, 200x).
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case_images: However, microscopic observation revealed the presence of a bilayered cell structure transitioning into tall columnar mucinous epithelium ( Figures 2A, B ), indicating the possibility of well-differentiated mucinous adenocarcinoma. A paraffin section of postoperative hematoxylin-eosin staining showed an unclear tumor boundary and a papillary structure with a skip growth pattern ( Figure 2C ). Within this nodule, extracellular mucus with a continuous basal cell layer, as well as a bilayered structure composed of ciliated cells or mucous cells growing along the alveolar wall, were observed ( Figure 2D ). Tall columnar mucous cells lacked cilia structures and were slightly atypical, with enlarged nuclei, an increased ratio of nucleus to cytoplasm, not easily visible mitotic figures and loss of basal cell layer ( Figures 2E, F ).
case_images: Hematoxylin and eosin and Immunohistochemical staining of the lesion area. The tumor consisted of two general areas: The area of BA (yellow line) and the area of IMA (red line) (A, 40x); P40 positive expression in basal cells in BA structures and basal cells in malignant IMA with absent expression (B, 40x and C, 100x). P63 positive expression in basal cells in BA structures and basal cells in malignant IMA with absent expression (D, 200x). CEA is continuously strongly and positively expressed in the BA structures (black arrow) and de-expressed in IMA structures (red arrow) (E, 100x and F, 200x). TTF1 is partially punctiformly expressed in BA structures (black arrow) and strongly positively expressed in IMA structures (red arrow) (G, 100x and H, 200x).
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case_images: Immunohistochemical expression showed that P40 and P63 markers were continuously expressed in the part of BA, whereas the positive expression of P40 and P63 was lost in the mucoid glandular structure ( Figures 3A-D ). The expression pattern of CEA was similar to that of P40 and P63 ( Figures 3E, F ). II alveolar epithelium and clara cells. In this case, TTF1 was expressed punctiformly in the glands of BA, but continuously and strongly positively in glands formed by highly columnar mucous cells ( Figures 3G, H ).