Fig. 3
(a) Nodular hyperplasia of MMPH multifocal alveolar epithelial cells at ×50 magnification. The lung shows scattered, multifocal, well-defined small nodules. (b) MMPH multifocal nodular hyperplasia of alveolar epithelial cells at ×100 magnification. The alveolar cavity narrows or collapses, with proliferation of alveolar epithelial cells. (c) MMPH multifocal nodular hyperplasia of alveolar epithelial cells at ×200 magnification. (d) MMPH multifocal nodular hyperplasia of alveolar epithelial cells at ×400 magnification. Alveolar epithelial cells proliferate, with most cells showing atypical features. The volume of both the cells and their nuclei increases, and pseudoinclusions or nucleoli are visible in some nuclei. (e) AAH at ×200 magnification. Small, localized lesions (usually ≤ 0.5 cm) show proliferated alveolar cells, which are round, cuboidal, or low columnar in shape, with round or oval nuclei. These cells display mild to moderate dysplasia and line the alveolar walls, occasionally extending into the respiratory bronchioles. Often, gaps between cells are present, and the cells do not form continuous clusters. (f) AIS adenocarcinoma in situ at ×200 magnification. It is composed of alveolar type II epithelium or Clara cells, with cancer cells growing strictly along the original alveolar wall. There is no evidence of other growth patterns, such as interstitial infiltration, vascular or pleural infiltration, or airway spread. (g) MIA at ×200 magnification. Part of the alveolar cavity is narrowed and collapsed, with homogeneous, gentle proliferation of alveolar epithelial cells along the alveolar wall. This forms a non-mucinous adenocarcinoma with an infiltration focus measuring less than 5 mm. (h) Bone marrow biopsy lesion map. Bone marrow biopsy confirmed active bone marrow hyperplasia, predominantly erythroid hyperplasia, with young red blood cells being the most common.
