Parvalbumin [PARV19]

Parvalbumin is a 12 kDa calcium-binding protein that modulates intracellular calcium dynamics. Capable of binding two calcium ions, parvalbumin functions as a relaxing factor that shuttles calcium ions from other calcium-binding proteins to buffer intracellular calcium. First detected in glycolytic skeletal muscle fibers, it is also expressed in the axons and terminals of cerebellar interneurons of the cerebellum, horizontal and ganglion cells of the retina, and distal convoluted tubules and connecting tubules in the kidney. In cancer, parvalbumin has been suggested as a useful marker for distinguishing primary and metastatic chromophobe renal cell carcinoma and renal oncocytoma from papillary renal cell and clear cell carcinomas. It stains 80-100% of chromophobe carcinomas and 69-82% of oncocytomas, compared to 0-8% clear cell and 0-31% papillary renal cell carcinomas. Sensitivity and specificity was determined as 80% and 89%, respectively. Although parvalbumin was evaluated in retinoblastoma, it was deemed to be a poor marker of tumor cells, labeling 0 of 52 cases.