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. 2014 Oct;6(Suppl 5):S526–S536. doi: 10.3978/j.issn.2072-1439.2014.01.27

Table 2. Diagnosis, terminology and recommendations in small specimens.

Pathologic characteristics 2004 WHO terminology IASLC/ATS/ERS terminology
Clear morphologic features present
   Presence of glands or mucin Adenocarcinoma. Patterns are described if clearly present Adenocarcinoma. Describe patterns if clearly present. Considerations: AIS/MIA cannot be diagnosed in small biopsies; if pure lepidic pattern/growth seen, add comment on invasive adenocarcinoma cannot be excluded nor assumed
   Presence of keratinization, pearls or intercellular bridges Squamous-cell carcinoma Squamous-cell carcinoma
No morphologic features but distinctive positive immunostaining
   TTF-1 (or napsin A) No specific terminology. Usually diagnosed as solid adenocarcinomas NSCLC-favor adenocarcinoma
   p63 (or p40 or CK 5/6) No specific terminology NSCLC-favor squamous-cell carcinoma
Conflicting results of morphology and IHC (Mixed) No clear recommendations Individualize. Considerations: adenosquamous tumors can only be diagnosed in resection specimens with >10% of each component present; almost all TTF-1 and p63 positive are adenocarcinomas
No differentiation by morphology or IHC (both negative) Large-cell carcinoma NSCLC-NOS. Considerations: avoid the use of the term large-cell carcinoma in small specimens (restricted to resection specimens); this term should be used as little as possible

WHO, World Health Organization; IASLC, International Association for the Study of Lung Cancer; ATS, American Thoracic Society; ERS, European Respiratory Society; AIS, adenocarcinoma in situ; MIA, minimally invasive adenocarcinoma; NSCLC, non-small-cell lung cancer; NOS, not otherwise specified; IHC, immunohistochemistry.