C91.9Lymphoid leukemia, unspecified

C91.9 is the ICD-10-CM diagnosis code for lymphoid leukemia, unspecified. It belongs to category C91 (lymphoid leukemia), block C81-C96 (malignant neoplasms of lymphoid, hematopoietic and related tissue) and chapter 2 (neoplasms). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within C91, choose C91.9 (unspecified) only when documentation doesn't support a more specific option: acute lymphoblastic leukemia [ALL] (C91.0), chronic lymphocytic leukemia of B-cell type (C91.1), Prolymphocytic leukemia of B-cell type (C91.3), Hairy cell leukemia (C91.4), adult T-cell lymphoma/leukemia (HTLV-1-associated) (C91.5), Prolymphocytic leukemia of T-cell type (C91.6), mature B-cell leukemia Burkitt-type (C91.A) and other lymphoid leukemia (C91.Z).

To report this condition, pick the subcode that matches the documentation: C91.90 (not having achieved remission), C91.91 (in remission) and C91.92 (in relapse).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.