1. Pulmonary Adenocarcinoma Patterns The good, the bad and the ugly C. Black 5-23-2014 CTOP retreat

2. 2004 WHO 4 major patterns of ADC – Bronchioloalveolar – Acinar – Papillary – Solid – Mixed (most common)

3. 2011 IASLC/ATS/ERS ADC re- classification Recommendation Discontinue use of the term BAC 1.Being used as ADC in-situ 2.Minimally invasive ADC 3.Invasive ADC with lepidic pattern 4.Invasive mucinous ADC

4. 2011 IASLC/ATS/ERS ADC re-classification Recommendation – Mixed sub-type discontinued – Predominant pattern used – Percentage estimates for mixed tumors

5. 2011 IASLC/ATS/ERS ADC re-classification Recommendation strength – Weak Low evidence for reproducibility….

6. Reproducibility of histopathological subtypes and invasion in pulmonary adenocarcinoma. An international interobserver study Modern 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

7. 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

8. 2011 IASLC/ATS/ERS ADC re- classification Recommendation Micropapillary ADC – added as major pattern

9. Current ADC Patterns 1.Acinar 2.Non-mucinous lepidic (former BAC) 3.Micropapillary 4.Papillary 5.Solid

10. Acinar

11. AIS (non-mucinous)

12. 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

13. 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 Microinvasive adenocarcinoma

14. Micropapillary Histopathology, Volume 46, Issue 6, pages 677– 684, June 2005 Human Pathology Volume 39, Issue 3, March 2008, Pages 324–330

15. Papillary

16. Solid

17. “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)”.

18. CTOP Case Tumor 1, 1.3 cm Tumor 2, 1.0 cm

20. Good – AIS, Microinvasive Bad – Acinar, Papillary Ugly – Solid, Micropapillary