This diagnostic package, based on immunohistochemistry, includes the examination of a range of markers to evaluate and diagnose tumors and diseases involving plasma cells. The package primarily includes the examination of CD138 (Syndecan-1), a highly sensitive membrane marker for mature plasma cells, along with essential complementary markers: Kappa Light Chain and Lambda Light Chain (for assessing plasma cell clonalness), and a proliferative marker such as Ki-67. The package aims to identify the presence of clonal (cancerous) pools of plasma cells, which is the key feature in the diagnosis of multiple myeloma and related diseases.