PMC7354012_01
Computed tomography (CT) scans of the chest. (A and B) Photographs present a well-circumscribed and lobulated 2.5-cm nodule in the right middle lobe.
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Chest computed tomography (CT) revealed a 2.5x1.5x1.5cm nodule in the right middle lobe, with no mediastinal lymph node enlargement or distant metastases (Figure 1). Molecular studies have revealed that these two lesions harbored distinct genetic mutations (Supplementary Figure 1).
Histological manifestations of L-FLAC and AIS. L-FLAC shows complex glandular structures, with prominent morule formation (A, 100x; B, 200x). The AIS presents tumor cells distributed along alveolar structures without stromal, vascular, and alveolar space invasion (C, 40x; D, 100x).
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In the second lesion, the tumor cells were distributed alongside the alveolar structures, without stromal, vascular, and alveolar space invasion, presenting a maximum diameter of only 2 mm (Figure 2C and D).
Immunophenotype of L-FLAC lesions. Immunohistochemically, the L-FLAC cells present diffuse staining of TTF-1 (A, 100x) and SALL4 (B, 100x); focal expression of CgA (C, 100x) and synaptophysin (D, 100x); and predominant membranous beta-catenin expression with only sporadic nuclear/cytoplasmic staining (E, 200x); The Ki-67 index is approximately 40% (F, 100x).
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Immunohistochemically, the L-FLAC cells presented diffuse staining for cytokeratin, thyroid transcription factor-1 (TTF-1, Figure 3A), epithelial membrane antigen (EMA), and sal-like protein 4 (SALL4, Figure 3B). Chromogranin A (CgA, Figure 3C) and synaptophysin (Figure 3D) were only focally stained. Notably, beta-catenin showed diffuse staining on the cell membrane, with only sporadic nuclear/cytoplasmic expression (Figure 3E). The Ki-67 index was approximately 40% (Figure 3F).