What is the primary characteristic of hematologic cancer?

Hematologic cancers are characterized primarily by their origin in the cells of the blood, bone marrow, and the immune system. These types of cancers include conditions such as leukemia, lymphoma, and myeloma, which directly involve hematopoietic (blood-forming) tissues. This means that the cancer develops from the blood cells (such as white blood cells) and the environments where these cells are produced, such as the bone marrow and lymphatic system.

The other options describe different categories of cancers. For instance, cancers that begin in solid tumors are typically referred to as solid tumors, which encompass a wide variety of malignant growths that can occur in organs and tissues throughout the body. Cancers affecting lymphatic tissues alone are more specific and do not encompass all hematologic cancers, as hematologic cancers also include those arising in bone marrow and peripheral blood. Lastly, cancers arising from epithelial cells refer to carcinoma types, which are entirely different from hematologic malignancies. Thus, the defining characteristic of hematologic cancer as originating in the bone marrow or immune system cells is essential for proper classification and understanding of these malignancies.