Spiral Tissue Microarray Covers Tissue Heterogeneity of Pulmonary Adenocarcinoma
S Tominaga, R Ohsawa, T Tanaka, S Shimizu, T Hori, J Fukuoka. Toyama University Hospital, Toyama, Japan
Background: We have recently developed a novel tissue microarray (TMA) technique named Spiral TMA (S-TMA). S-TMA block can be constructed not by coring the tissue from donor block but by embedding multiple reeled thick-cut specimens vertically to a designed recipient block. Its two biggest advantages are that it is applicable to the block with limited tissue and skip damaging donor blocks by coring. It is also assumed that it may cover tissue heterogeneity more than conventional TMA (c-TMA). Lung cancer is one of the tumor with vast tissue heterogeneity where commonest histological subtype is a mixed subtype. Tissue heterogeneity likely reflects difference of molecular biology in each subtype, and for the molecular expression analysis, it is not a negligible factor. To examine if S-TMA covers tissue heterogeneity more than c-TMA, we immunohistochemically investigated the degree of heterogeneity covered by each TMA.
Design: Recent 25 pulmonary adenocarcinoma cases were selected from archives of Toyama University Hospital. S-TMA was constructed with 100 micron thick sections of the blocks. c-TMA with 2mm cores was also constructed. MIB-1, EGFR and CK7, known to have tissue heterogeneity with various degrees were selected. MIB-1 index was scored in areas with both highest and lowest percentage at HPF. For EGFR and CK7, Intensity Score (IS) was divided into 4 degree; 0,none; 1,weak; 2,moderate; 3,strong. Areas with both strongest and weakest IS were scored for EGFR and CK7. The heterogeneity was evaluated by the subtraction between those two scores. Student t test and Mann-Whitney's U test was used for the statistical analysis.
Results: Areas seen in S-TMA ranged from 1.0 to 2.04mm2 (mean 1.44mm2), while those in c-TMA were always 3.14mm2. Six cases in c-TMA showed < 1% of MIB-1 index while 3 cases in S-TMA showed < 1% of index. In EGFR and CK7, c-TMA showed 7 and 1 negative cases, respectively, while S-TMA showed 8 and 0. The range of MIB-1 index was significantly larger in S-TMA than in c-TMA. (p=0.04). The range of IS was also significantly larger in S-TMA than c-TMA in both EGFR and CK7 (p < 0.01).
Conclusions: Our results indicate that Spiral TMA covered tissue heterogeneity significantly more than conventional TMA which was confirmed by expressions of MIB-1, EGFR and CK7, even with smaller areas than conventional TMA included in the array slides. S-TMA may be a useful tool to examine biomarkers in disorders with high tissue heterogeneity.
Monday, March 22, 2010 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 259, Monday Morning