PMC7254091_01
Axial CT images. (a) A chest CT image obtained 7 days after the initial visit shows a large infiltrative shadow, as well as a small infiltrative shadow that is suspected to be a skip lesion (arrow). (b) A chest CT image obtained 2 months after left lobectomy shows an infiltrative shadow with a skip lesion (arrow) in the right lung.
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fig1
Seven days later, chest CT demonstrated the expansion of the shadow and a small infiltrative shadow suggestive of a skip lesion (Figure 1(a)). Two months postoperatively, a follow-up chest CT revealed an infiltrative shadow with an approximate diameter of 6 cm and a skip lesion in the lower lobe of the right lung (Figure 1(b)).
Left lung cancer I. (a) Gross view showing an ill-defined tumor with a diffuse pneumonia-like consolidation. Scale bar: 1 cm. (b) The tumor cells exhibit lepidic or papillary growth, with detached tumor cells scattered in the alveolar spaces. Hematoxylin and eosin (H&E) staining, scale bar: 2 mm. (c) Columnar tumor cells with intracytoplasmic vacuoles are shown in a monolayer arrangement. H&E stain, scale bar: 200 mum. (d) Multiple mucin-producing tumor cells are visible. Alcian blue stain, scale bar: 200 mum.
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fig2
Macroscopically, the resected tumor was ill-defined and gelatinous with a diffuse pneumonia-like consolidation (Figure 2(a)). Histopathologically, the majority of the tumor cells were columnar, contained varying amounts of intracytoplasmic mucins, and exhibited lepidic or papillary growth in a single-layer arrangement (Figures 2(b)-2(d)).
Left lung cancer II. (a) Small groups of tumor cells that detached from the alveolar wall. Only a slight inflammatory cell infiltration is visible. H&E stain, scale bar: 200 mum. (b) Detached tumor cells with a micropapillary pattern float within the alveolar spaces. H&E stain, scale bar: 200 mum. (c) The invasive component exhibits glandular or papillary growth. H&E stain, scale bar: 1 mm. (d) Many scattered tumor cell aggregates that detached from the primary tumor are visible within the air spaces and on the alveolar wall. The latter aggregates exhibit lepidic or papillary growth that is suggestive of microscopic aerogenous metastases. H&E stain, scale bar: 2 mm.
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fig3
Small groups of tumor cells had detached from the alveolar wall and were scattered diffusely (Figure 3(a)). Tumor cell aggregates floating within the alveolar spaces were round-shaped but had apical-basal polarity (Figure 3(b)). The apical surface of the tumor cells was located at the outer edge of the aggregates but naturally lacked central fibrovascular cores (Figure 3(b)), corresponding to the micropapillary pattern of the three morphological patterns of STAS. These foci had a glandular or papillary structure (Figure 3(c)) and greatly reduced levels of intracytoplasmic mucins. The latter aggregates exhibited lepidic or papillary growth that is suggestive of microscopic AMs (Figure 3(d)).
Immunostaining of mucin glycoproteins in the left lung tumor. (a) Diffuse cytoplasmic positivity is visible in the lepidic or papillary component, and positive staining is present in the alveolar spaces (arrows). MUC 5AC immunostain, scale bar: 200 mum. (b) Floating tumor cells exhibit the same positive reaction. MUC 5AC immunostain, scale bar: 100 mum. (c) Some tumor cells exhibit cytoplasmic positivity. MUC 6 immunostain, scale bar: 200 mum. (d) In some cells, positive staining is visible on the cell surfaces but not in the cytoplasm. MUC 1 immunostain, scale bar: 100 mum.
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In the left lung tumor, the majority of tumor cells were positive for MUC 5AC (Figures 4(a) and 4(b)) and CK7 (data not shown). Abundant positive MUC 5AC staining was also observed in the alveolar spaces (Figures 4(a) and 4(b)). Taiwan; Figure 4(c)). Additionally, some tumor cells exhibited a positive MUC 1 reaction at the cell surface but not in the cytoplasm (Figure 4(d)), in contrast to our previously reported case.
ANX A2 and collagen IV immunostaining of the lepidic or papillary component of the left lung tumor. (a) Tumor cells exhibit cytoplasmic ANX A2 positivity on the basal side. ANX A2 immunostain, scale bar: 400 mum. (b) A linear positive collagen IV reaction corresponding to the basement membrane is seen on the surfaces of both alveolar and vessel walls. Collagen IV immunostain, scale bar: 400 mum. (c) Detached tumor cells also exhibit cytoplasmic ANX A2 positivity on the basal side but not at the cell-cell borders. Positive staining is also observed in the exfoliative gap. ANX A2 immunostain, scale bar: 100 mum. (d) Weak or no collagen IV positivity is visible at the detachment site (arrows). Collagen IV immunostain, scale bar: 100 mum.
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As shown in Figures 5 and 6 (5(a), 5(c), 6(a), and 6(b) show ANX A2 staining), granular cytoplasmic ANX A2 positivity was observed on the basal sides of tumor cells exhibiting lepidic or papillary growth (Figure 5(a)), whereas no positive signal was detected at the cell-cell borders. ANX A2 positivity near the cell surfaces. A similar expression pattern was observed in the detached tumor cells, and positive expression was also observed in the exfoliation gap (Figure 5(c)). As shown in Figures 5 and 6 (5(b), 5(d), and 6(c) show collagen IV staining), the lepidic or papillary area exhibited linear positive collagen IV staining corresponding to the BM, which was detected in both the surfaces of the alveolar and vessel walls (Figure 5(b)). However, either weak positivity or no signal was observed at the detachment site (Figure 5(d)).
Floating tumor cells (a) and invasive components (b and c) of the left lung tumor. (a) No distinct ANX A2 positivity is visible in the floating tumor cells within alveolar spaces. ANX A2 immunostain, scale bar: 100 mum. (b) Stronger cytoplasmic ANX A2 positivity is observed on the basal side, and positive staining is visible at the cell-cell borders. ANX A2 immunostain, scale bar: 200 mum. (c) The desmoplastic stroma exhibits positive collagen IV staining, particularly around the tumor cells. Collagen IV immunostain, scale bar: 1 mm.
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As shown in Figures 5 and 6 (5(a), 5(c), 6(a), and 6(b) show ANX A2 staining), granular cytoplasmic ANX A2 positivity was observed on the basal sides of tumor cells exhibiting lepidic or papillary growth (Figure 5(a)), whereas no positive signal was detected at the cell-cell borders. Noticeably, weaker ANX A2 positivity was observed in the tumor cells floating within the alveolar spaces (Figure 6(a)). In the invasive component, stronger cytoplasmic positivity on the basal side was observed relative to that observed in the lepidic or papillary growth component (Figure 6(b)), and membranous positivity was observed on the cell-cell borders (Figure 6(b)). As shown in Figures 5 and 6 (5(b), 5(d), and 6(c) show collagen IV staining), the lepidic or papillary area exhibited linear positive collagen IV staining corresponding to the BM, which was detected in both the surfaces of the alveolar and vessel walls (Figure 5(b)). In the invasive area, the desmoplastic stroma exhibited positive staining for collagen IV (Figure 6(c)), thus suggesting the presence of cancer-associated fibroblasts and neogenic collagen.
ANX A2 immunostaining of microscopic aerogenous metastases in the left lung. (a) No distinct positivity is visible in the minute foci. Scale bar: 200 mum. (b) Basal-side cytoplasmic positivity is detected in the larger metastatic foci. Scale bar: 200 mum.
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In an analysis of the AM, no positive reaction to ANX A2 beyond weak staining near the cell surface was observed in the minute foci (i.e., tumor cells that had newly adhered to the alveolar wall; Figure 7(a)). However, the staining patterns in larger foci became similar to those observed in the lepidic or papillary growth component of the primary lesion (Figure 7(b)).