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I.S. Sarkaria

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    MO26 - Anatomical Pathology II (ID 129)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Pathology
    • Presentations: 1
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      MO26.04 - Reclassification of Resected Non-Small Cell Lung Carcinomas Originally Diagnosed as Squamous Cell Carcinoma, after Reevaluation Using Immunohistochemical Analysis (p40, p63, TTF-1, and Napsin A): Memorial Sloan-Kettering Cancer Center Experience (ID 2905)

      10:30 - 12:00  |  Author(s): I.S. Sarkaria

      • Abstract
      • Presentation
      • Slides

      Currently, non-small cell lung carcinomas (NSCLCs) are mainly classified by histologic analysis and mucin staining: (1) squamous cell carcinoma (SCC) shows keratinization and intercellular bridges; (2) adenocarcinoma shows lepidic, acinar, papillary, micropapillary, or solid pattern, with mucin production; and (3) large cell carcinoma lacks these findings. However, recent studies have shown promising improvements in the classification of NSCLC with immunostain-based markers, including p40 and thyroid transcription factor–1 (TTF-1). In this study, we investigate the use of immunohistochemical analysis in reclassifying NSCLCs originally diagnosed as SCCs.

      All available tumor slides from patients with therapy-naive, surgically resected solitary NSCLCs originally diagnosed as SCC (1999-2009) were reviewed. Tissue microarrays were constructed with 3 cores (n=480), and immunostaining for p40, p63, TTF-1 (clone 8G7G3/1), TTF-1 (SPT24), napsin A, chromogranin A, synaptophysin, and CD56 was performed. Immunoreactivity was scored semiquantitatively by staining intensity (weak, moderate, or strong) and percentage of positive tumor cells (diffuse, ≥50%; focal, <50%). Tumors were first grouped by p40 and TTF-1 (8G7G3/1) status: (1) group A (favor SCC): p40 (+) and TTF-1 (8G7G3/1) (-); (2) group B (favor adenocarcinoma): p40 (- or +) and TTF-1 (8G7G3/1) (+); and (3) group C (favor large cell carcinoma): p40 (-) and TTF-1 (8G7G3/1) (-). Immunostain-based tumor classification was then confirmed with histologic findings and other markers.

      In group A (n=448), 1 tumor was reclassified as adenosquamous carcinoma by histologic findings and focal immunoreactivity for p40, p63, and TTF-1 (SPT24). In group B (n=15), 2 tumors were reclassified as large cell neuroendocrine carcinoma (LCNEC) by neuroendocrine morphologic findings and differentiation (1 as pure LCNEC and the other as combined LCNEC with SCC). In group C (n=17), 6 tumors were confirmed as large cell carcinoma because they lacked adenocarcinoma morphology and TTF-1 [SPT24] expression (2 of these showed focal p63 reactivity without keratinization); 4 were reclassified as large cell carcinoma (favor adenocarcinoma) because they were focally positive for TTF-1 (SPT24) but negative for TTF-1 (8G7G3/1) and napsin A; 2 were reclassified as adenocarcinoma because they were diffusely and strongly positive for TTF-1 (SPT24) but focally (<10%) positive for p63, without keratinization; 3 were reclassified as LCNEC by neuroendocrine morphologic findings and differentiation; and 2 were reclassified as small cell carcinoma by morphologic findings. All tumors finally diagnosed as SCC (n=447) using histologic findings and immunohistochemical analysis were positive for p40 and p63. Among them, 27 tumors were positive for TTF-1 (SPT24) (19 focally and 8 diffusely) but negative for TTF-1 (8G7G3/1), with all showing clear squamous morphologic pattern, thus verifying the greater specificity of the TTF-1 8G7G3/1 clone in SCC.

      After immunohistochemical reevaluation of 480 NSCLCs originally diagnosed as SCC by classical morphologic analysis, 33 (7%) were reclassified as other histologic types. Immunohistochemical analysis may provide additional valuable information to achieve an accurate diagnosis, particularly in poorly differentiated NSCLCs and in tumors for which the diagnosis of nonkeratinizing SCC is considered.

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