In Situ Hybridization (ISH) for Lambda Light Chains is a molecular test that evaluates abnormal lambda light chain expression in related blood cells. Hematological malignancies, commonly plasma cell disorder and multiple myeloma, are evaluated for abnormal light chain production. It involves studying specific fluorescent probes binding to lambda light chain mRNA. Tests aid in the diagnosis, therapeutic management, and prognostication of plasma cell dyscrasias.