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Pulmonary Adenocarcinoma Patterns. The good, the bad and the ugly. C. Black 5-23-2014 CTOP retreat. 2004 WHO. 4 major patterns of ADC Bronchioloalveolar Acinar Papillary Solid Mixed (most common). 2011 IASLC/ATS/ERS ADC re-classification. R ecommendation
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Pulmonary Adenocarcinoma Patterns The good, the bad and the ugly C. Black 5-23-2014 CTOP retreat
2004 WHO • 4 major patterns of ADC • Bronchioloalveolar • Acinar • Papillary • Solid • Mixed (most common)
2011 IASLC/ATS/ERS ADC re-classification Recommendation • Discontinue use of the term BAC • Being used as ADC in-situ • Minimally invasive ADC • Invasive ADC with lepidic pattern • Invasive mucinous ADC
2011 IASLC/ATS/ERS ADC re-classification Recommendation • Mixed sub-type discontinued • Predominant pattern used • Percentage estimates for mixed tumors
2011 IASLC/ATS/ERS ADC re-classification • Recommendation strength – Weak • Low evidence for reproducibility….
Reproducibility of histopathological subtypes and invasion in pulmonary adenocarcinoma. An internationalinterobserver studyModern Pathology (2012) • 26 pathologists, 115 cases • micro photographic images of ADCs • Mix of typical and difficult cases • Mean kappa scores: 0.77+/-0.07 typical 0.38+/-0.14 difficult • Highest correlation for solid and least for micro papillary
Identification of Invasion versus in-situ (28 pathologists/64 images) Kappa scores: 0.55+/-0.06 typical cases 0.08+/-0.02 difficult cases Consistent subdivisions suggesting educational bias
2011 IASLC/ATS/ERS ADC re-classification • Recommendation • Micropapillary ADC – added as major pattern
Current ADC Patterns • Acinar • Non-mucinous lepidic (former BAC) • Micropapillary • Papillary • Solid
AIS • Non-mucinous lepidic • Localized small (≤3 cm) adenocarcinoma • Growth restricted to neoplastic cells along preexisting alveolar structures (lepidic growth) • Lacking stromal, vascular, or pleural invasion
Microinvasive adenocarcinoma A, lepidic growth with a small (<0.5 cm) central area of invasion. B, To the left is the lepidic pattern and on the right is an area of acinar invasion. C, These acinar glands are invading in the fibrous stroma. IASLC, JCO 2011
Micropapillary • Histopathology, Volume 46, Issue 6, pages 677–684, June 2005 Human Pathology Volume 39, Issue 3, March 2008, Pages 324–330
“In patients with multiple lung adenocarcinomas, we suggest comprehensive histologic subtyping may facilitate in the comparison of the complex, heterogeneous mixtures of histologic patterns to determine whether the tumors are metastases or separate synchronous or metachronous primaries (weak recommendation, low-quality evidence)”.
CTOP Case Tumor 1, 1.3 cm Tumor 2, 1.0 cm
Good – AIS, Microinvasive • Bad – Acinar, Papillary • Ugly – Solid , Micropapillary