What is a key characteristic finding in the peripheral smear of a patient with multiple myeloma?

Rouleaux formation is a key characteristic finding in the peripheral smear of a patient with multiple myeloma. This phenomenon occurs when red blood cells stack together in a manner reminiscent of a stack of coins. It is often associated with conditions that increase the levels of abnormal proteins in the blood, which is a hallmark of multiple myeloma due to the excessive production of monoclonal immunoglobulins by malignant plasma cells.

In multiple myeloma, the increase in these proteins leads to a change in the rheological properties of blood, thus causing red blood cells to lose their normal negative charge, resulting in this clustering. Identifying rouleaux formation can aid in the diagnosis of multiple myeloma, as it is less commonly seen in other hematologic disorders.

Other findings, such as microcytic red blood cells, might indicate iron deficiency anemia but are not specifically linked to multiple myeloma. The presence of giant platelets could be associated with various conditions including myeloproliferative disorders, but again, not directly with multiple myeloma. A decreased neutrophil count may occur in a variety of hematologic conditions, but it is not distinctive for multiple myeloma. Therefore, rouleaux formation stands out as a