Cyclooxygenase 2 (Cox 2) Expression in Newly Diagnosed Plasma Cell Myeloma: A Clinicopathological and Immunohistochemical Study on 73 Cases from a Single Tertiary Care Center.

To study the cyclooxygenase 2 (Cox 2) expression in newly diagnosed plasma cell myeloma cases by immunohistochemistry (IHC) and correlate with clinicohematological characteristics. Immunohistochemical expression of Cox 2 on bone marrow trephine biopsy was studied in seventy-three newly diagnosed myeloma cases [56 males, 17 females, median age; 58 years (36-75)] and fifteen controls using SP21 clone antibody. A median immuno-score (proportion x intensity) stratified the entire cohort into low and high expressors. Cox 2 immunoexpression was compared and correlated with clinicolaboratory characteristics and marrow histomorphology and survival. Twenty one of 73 (38.7%) cases had a plasmablastic morphology whereas remainder fifty-two (61.3%) had a differentiated morphology. The Cox 2 expression was noted in 71/73 (97.2%) cases (median score = 127.3) and 15/15 (100%) controls. Low expressors was associated with higher circulating plasma cells, increased marrow tumor burden, blastic morphology, and lower proliferation index (p < 0.05) with a peculiar 'dot-block' cytoplasmic positivity (p < 0.001); whereas high expressors had thinned out bony trabeculae with granular cytoplasmic positivity with or without membrane accentuation (p < 0.001). Cox 2 expression had a weak negative correlation with tumor burden (r; -0.32, p = 0.01) and positive correlation with proliferation index (r; 0.29, p = 0.03). There was no statistically significant difference in the survival between low (n = 20) and high (n = 23) expressors (log rank p = 0.11). A high proportion of myeloma cells in our cohort expressed Cox 2 using SP21 clone; and this may have a role in futuristic research and therapy.