In simple words: Lymphoid leukemia is a type of blood cancer where the bone marrow makes too many abnormal lymphocytes (a type of white blood cell). These abnormal cells crowd out healthy blood cells, leading to various symptoms like fatigue, fever, and swollen lymph nodes.

A malignant lymphocytic neoplasm of B-cell or T-cell lineage involving primarily the bone marrow and the peripheral blood. This category includes precursor or acute lymphoblastic leukemias and chronic leukemias.It's a progressive, proliferative disease of blood cells, originating from lymphoid cells. The bone marrow produces too many lymphocytes (a type of white blood cell). Leukemia is associated with hyperplasia and overactivity of the lymphoid tissue; there are increased numbers of circulating malignant lymphocytes and lymphoblasts.

Example 1: A patient presents with fatigue, swollen lymph nodes, and frequent infections. Blood tests reveal an elevated white blood cell count and abnormal lymphocytes. A bone marrow biopsy confirms the diagnosis of acute lymphoblastic leukemia (ALL), which would be coded as C91.0., A patient with chronic lymphocytic leukemia (CLL) experiences worsening symptoms, including enlarged spleen and anemia. After further evaluation, they begin treatment with chemotherapy. CLL, depending on the specific type, would generally be coded as C91.1., A child presents with bone pain, fever, and pallor. Blood tests show abnormal lymphocytes, and a bone marrow biopsy confirms the diagnosis of acute lymphoblastic leukemia (ALL), which would be coded as C91.0.

Documentation should include complete blood count (CBC) results, bone marrow biopsy findings, cytogenetic and immunophenotypic studies, and any relevant imaging or other test results. Clinical findings such as swollen lymph nodes, fatigue, and other symptoms should also be documented.

** Excludes1: personal history of leukemia (Z85.6)