LDH Interpretation in the Evaluation of Generalized Lymphadenopathy

LDH Thresholds for Specific Lymphoid Malignancies

The International Society for Lymphoid Oncology (NCCN) defines acute adult T‑cell leukemia/lymphoma (ATL) and the ATL lymphoma subtype as requiring an LDH level greater than twice the laboratory upper limit of normal (ULN), whereas chronic ATL is characterized by LDH below twice the ULN and smoldering ATL by LDH below 1.5 × ULN. A measured LDH of 122 U/L (well under these thresholds) makes these ATL forms highly unlikely. 3

Infections (e.g., viral, tuberculous) and inflammatory/autoimmune conditions that cause lymphadenopathy typically present with normal or only mildly elevated LDH, so a low LDH does not contradict a benign etiology. 3

Excisional lymph‑node biopsy is required for definitive diagnosis because LDH alone cannot differentiate benign from malignant lymphadenopathy. 3
Cross‑sectional imaging (CT of neck, chest, abdomen, and pelvis) should be performed to assess the extent of nodal involvement and to identify possible extranodal disease. 3
Bone‑marrow biopsy is indicated when histologic findings suggest marrow involvement or when staging of a confirmed lymphoma is required. 3
Targeted infectious work‑up includes testing for tuberculosis in patients with relevant exposure or epidemiologic risk. 3
HTLV‑1 serology should be considered in individuals from endemic regions or with risk factors, although a low LDH makes ATL unlikely. 3