A Panel of Immunohistochemistry To Differentiate Various WHO Types of Thymic Neoplasms
T Khoury, G Wilding, R Chandrasekhar, S Alrawi, D Tan. Roswell Park Cancer Institute, Buffalo; University of Florida, Jacksonville; MD-Anderson Cancer Center, Houston
Background: Classifying thymic neoplasms according to the World Health Organization (WHO) scheme is somewhat difficult. Recognizing specific types, particularly B3 and C is crucial in patient management and outcome. The purpose of this study is to integrate histologic features adopted by WHO with immunohistochemistry to help properly classify thymic neoplasms, particularly types B3 and C.
Design: A series of 63 thymic neoplasms were reviewed and classified according to the WHO scheme. Three tissue microarray blocks were constructed. The following immunostains were studied, D2-40, Thromomodulin, CK5/6, Podoplanin, Mesothelin, CD57, CD20, CD5, TdT, CD1a, CD138, CD117, EMA, CD15, MOC-31 and BerEpi-4. Proper scoring system was used for each marker. Presence or absence of tumor eosinophilia was recorded. Statistical analyses for categorical variables were performed using Fisher's exact test.
Results: There were 8 type A, 16 type AB, 8 type B1, 5 type B2, 16 type B3, and 10 type C thymomas. Table1 summarizes the statistically significant markers that differentiate various thymoma types.
Conclusions: We suggest an algorithm combining morphology and IHC to properly classify thymic neoplasms with emphasis on types B3 and C.
Panels of statistically significant IHC in various WHO types combinations*CD138 has to be diffuse and strong to be positive; ** EMA positive when luminal expression ; ***CD20 positive expression in epithelium ; ^TdT and CD1a positive when more than 10% of lymphocytes; ^^CD138 positive when at least mild staining
|WHO type||Markers||Frequency #positive (%)|
|A vs. AB||CD138*||7 (87.5) vs. 0 (0)|
|EMA**||6 (75) vs. (0)|
|B1 vs. B2 and B3||CD57||0 (0) vs. 11 (52.4)|
|B1 and B2 vs. B3||None||NA|
|A and AB vs. B1, B2 and B3||CD20***||10 (41.7) vs. 2 (7)|
|TdT^||14 (58.3) vs. 26 (89.7)|
|CD1a^||11 (45.8) vs. 26 (89.7)|
|CD138^^||20 (83.3) vs. 13 (44.8)|
|A and AB vs. B3||CD1a^||11 (45.8) vs. 13 (81.3)|
|B3 vs. C||CK 5/6||15 (93.8) vs. 3 (30)|
|Mesothelin||0 (0) vs. 5 (50)|
|CD57||8 (50) vs. 0 (0)|
|CD5||0 (0) vs. 6 (60)|
|TdT^||13 (81.3) vs. 1 (10)|
|CD1a^||13 (81.3) vs. 2 (20)|
|CD117||1 (6.3) vs. 7 (70)|
|Eosinophilia||1 (6.3) vs. 9 (90)|
Monday, March 9, 2009 1:00 PM
Poster Session II # 216, Monday Afternoon