ABSTRACT
Context: The diagnosis of giant cell tumor of bone (GCTB) is difficult in small biopsies with unusual age of presentation, location, and extensive secondary changes. Most of the GCTBs harbor H3F3A G34W mutations with a subset of cases showing alternate G34V, G34R, and G34L mutations. Objectives: To analyze the expression of anti-histone H3.3G34W antibody in different cellular components of GCTB across different locations and presentations (including the unusual ones) and validate the utility of this antibody in the diagnosis of GCTB and differentiate it from the other osteoclast-like giant-cell-rich lesions. Design: Immunohistochemistry was performed using anti-histone H3.3G34W antibody in the diagnosed cases of GCTB (136 cases of GCTB from 133 patients, including two malignant GCTBs) and other giant cell-containing lesions (62 cases). The presence of unequivocal crisp nuclear staining was considered positive. Results: Immunohistochemistry revealed unequivocal nuclear positivity in the mononuclear cells in 87.3% of the cases of GCTB. Of these, most showed diffuse expression with moderate to strong intensity staining. The positive staining was restricted to the nuclei of mononuclear cells with the nuclei of osteoclastic giant cells being distinctly negative. In addition to conventional GCTBs, two cases each of multicentric and malignant GCTB showed positive staining. The other giant-cell containing lesions were distinctly negative. The present study showed a sensitivity of 87.3% with specificity and positive predictive value of 100%. Conclusion: The anti-histone G34W antibody is a highly sensitive and specific marker for the diagnosis of GCTB and differentiating it from its mimics. The positive staining is restricted to the mononuclear cell component of GCTB with sparing the osteoclastic giant cells further reiterating the fact that the mononuclear stromal cells are the true neoplastic component of GCTB.
ABSTRACT
Background & objectives: Anthrax caused by Bacillus anthracis is primarily a disease of herbivorous animals, although several mammals are vulnerable to it. ELISA is the most widely accepted serodiagnostic assay for large scale surveillance of cutaneous anthrax. The aims of this study were to develop and evaluate a quantitative ELISA for determination of IgG antibodies against B. anthracis protective antigen (PA) in human cutaneous anthrax cases. Methods: Quantitative ELISA was developed using the recombinant PA for coating and standard reference serum AVR801 for quantification. A total of 116 human test and control serum samples were used in the study. The assay was evaluated for its precision, accuracy and linearity. Results: The minimum detection limit and lower limit of quantification of the assay for anti-PA IgG were 3.2 and 4 μg/ml, respectively. The serum samples collected from the anthrax infected patients were found to have anti-PA IgG concentrations of 5.2 to 166.3 μg/ml. The intra-assay precision per cent CV within an assay and within an operator ranged from 0.99 to 7.4 per cent and 1.7 to 3.9 per cent, respectively. The accuracy of the assay was high with a per cent error of 6.5 - 24.1 per cent. The described assay was found to be linear between the range of 4 to 80 ng/ml (R2=0.9982; slope=0.9186; intercept = 0.1108). Interpretation & conclusions: The results suggested that the developed assay could be a useful tool for quantification of anti-PA IgG response in human after anthrax infection or vaccination.