186 Chapter 14 Figure 7. Flow Diagram with morphological approach on invasion in pulmonary adenocarcinoma 1) Architectural change by the tumour also determined in CK7 and elastin stain 2) Iatrogenic collapse and monolayer of cells. Due to tangential cutting multilayering may occur in part of alveolar structures 3) Elastin stain info in review Histopathology 2021206 4) Noguchi type A: AIS with lepidic growth on thin alveolar septa. 5) Noguchi type B: AIS with increased amount of elastin causing slightly thickened alveolar septa (iatrogenic +/- biological collapse) 6) Papillary carcinoma does not produce elastin; fragmented elastin is normal and denotes alveolar walls. 7) Gland-like structures, in area without pre-existing alveoli, usually have a “glandular” diameter <<200 µm (size of average alveolus) and is therefore called “small” acinar adenocarcinoma; usually no elastin in between the gland-like structures. Small acinar adenocarcinoma may also invade in the interstitium of alveolar walls. 8) No dissociation and distinct multilayering in several adjacent alveoli: uncertain, more data required; for time being designated as invasive. 9) This typically is the micropapillary pattern laying lining the pre-existing alveolar wall 10) implies cases with complete effacement of pre-existing architecture, but may also be cases with lepidic growth and focal features invasion. 11) Solid adenocarcinoma contains alveolar filling with tumour cells, invasion of individual tumour cells, small strands of tumour cells and/or larger interstitial fields of tumour. Individual cells and strands of cells are frequently embedded in desmoplastic stroma (loose fibromyxoid stroma). 12) Cribriform is intra-alveolar growth with epithelial proliferation with a “gland-in-gland” formation. This prevents iatrogenic collapse and has in the elastin stain only elastin on the outside. 13) Only growth on alveolar walls (lepidic growth) with or without iatrogenic collapse. 14) Increased elastin and no other signs of invasion (NOSI): Biological collapse, where in the elastin stain the pre-existing alveolar structure can easily be recognized usually in association with increased elastin in alveolar walls with lepidic growth: Also Noguchi type B. In this pattern the CK7 stain may show comma like CK7 positive structure in the region close to collapse without CK7 positivity. 15) The area with multilayering is defined as fully present in at least a few adjacent alveoli. Not infrequently the lobular unit has the same appearance. 16) Loss of cellular cohesion. 17) Lepidic in association with true morphological signs of invasion in non-lepidic part 18) Beside lymphangio-, bronchial- and pleural invasion 18) No real invasion observed but presence is associated with other signs of invasion (true invasion, lymphogenic and/or haematogenic invasion 19) Multilayering / stratification in >=3 alveolar structures, which fall short of the minimum criteria for micropapillary (3 cells tall, 2 cells wide) 20) MIA is not used, see discussion. 21) STAS is not undisputed; not used.
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