text: 4.2. Histological Findings
  Microscopy revealed features of a diffusely growing discohesive carcinoma, exclusively growing in the alveolar interstitium, thus expanding it, while leaving the original alveolar architecture intact (Figure 2). There was local ulceration of the pleura, while, beyond this ulcer, the tumor formed a thick cake of discohesive tumor cells lining the pleural membrane (Figure 2(c)), with only focal, microscopic invasion into the fatty tissue of the parietal pleura.
  The tumor consisted of atypical, moderately polymorphous, and irregularly shaped tumor cells with marked discohesiveness. They featured scant eosinophilic cytoplasm and irregularly contoured and hyperchromatic nuclei, often containing one or more prominent nucleoli (Figure 2(b)). There were many mitoses and apoptoses present, but necrosis was not observed. No squamous or glandular differentiation was observed, and mucin stains (PAS-D and alcian blue) were negative. Within the tumor, there were multiple small blood-filled clefts and blood lakes. Angioinvasion in medium-sized vessels, including an artery, was demonstrated (Figure 2(d)).
  Of note, the broadened alveolar septa were lined by markedly atypical epithelial cells, yet less atypical than the interstitial carcinoma (Figures 2(a) and 2(b)). The atypia of the lining cells extended beyond the tumor front, showing a sharp demarcation with normal type I pneumocytes (Figure 2(a)), a feature characteristic to nonmucinous adenocarcinoma in situ with lepidic growth pattern (former bronchioloalveolar carcinoma, BAC) [3].
  
entities.text: ['discohesive carcinoma']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T1
entities.text: ['alveolar interstitium']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T2
entities.text: ['alveolar']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T3
entities.text: ['pleura']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T4
entities.text: ['ulcer']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T5
entities.text: ['tumor']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T6
entities.text: ['discohesive tumor cells']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T7
entities.text: ['pleural membrane']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T8
entities.text: ['fatty tissue']
entities.type: Tissue
entities.entity_id: PMC-3135183-sec-06_T9
entities.text: ['parietal pleura']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T10
entities.text: ['tumor']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T11
entities.text: ['tumor cells']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T12
entities.text: ['eosinophilic cytoplasm']
entities.type: Organism_substance
entities.entity_id: PMC-3135183-sec-06_T13
entities.text: ['nuclei']
entities.type: Cellular_component
entities.entity_id: PMC-3135183-sec-06_T14
entities.text: ['nucleoli']
entities.type: Cellular_component
entities.entity_id: PMC-3135183-sec-06_T15
entities.text: ['squamous']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T16
entities.text: ['glandular']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T17
entities.text: ['tumor']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T18
entities.text: ['blood']
entities.type: Organism_substance
entities.entity_id: PMC-3135183-sec-06_T19
entities.text: ['blood']
entities.type: Organism_substance
entities.entity_id: PMC-3135183-sec-06_T20
entities.text: ['vessels']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T21
entities.text: ['artery']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T22
entities.text: ['alveolar septa']
entities.type: Multi-tissue_structure
entities.entity_id: PMC-3135183-sec-06_T23
entities.text: ['epithelial cells']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T24
entities.text: ['interstitial carcinoma']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T25
entities.text: ['lining cells']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T26
entities.text: ['tumor']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T27
entities.text: ['type I pneumocytes']
entities.type: Cell
entities.entity_id: PMC-3135183-sec-06_T28
entities.text: ['nonmucinous adenocarcinoma']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T29
entities.text: ['bronchioloalveolar carcinoma']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T30
entities.text: ['BAC']
entities.type: Pathological_formation
entities.entity_id: PMC-3135183-sec-06_T31