Acute Myelomonocytic Leukemia Misdiagnosed as Histiocytic Necrotizing Lymphadenitis.

Abstract

Background: Acute Myelomonocytic Leukemia (AMML) is a rare malignant neoplasm that is classified as a subtype of Acute Myeloid Leukemia (AML). In the case described herein, the initial pathology results from a lymph node biopsy leaned towards Histiocytic Necrotizing Lymphadenitis, but ultimately, immunohistochemistry of the lymph node confirmed the diagnosis of Acute Myelomonocytic Leukemia.

Methods: Cervical lymph node biopsy.

Results: In this case, the initial pathological diagnosis after cervical lymph node biopsy favored histiocytic necrotizing lymphadenitis. However, immunohistochemical analysis revealed the presence of immature cell proliferation in the lightly stained areas, characterized by irregular nuclear shapes and visible mitotic figures. Further investigation showed that these immature cells were positive for CD68 and Lys, weakly positive for myeloperoxidase (MPO), and partially positive for CD4, CD8, granzyme B (GrB), and TIA1. The Ki67 proliferation index was approximately 70%, indicating a high rate of cell proliferation. Based on these immunohistochemical findings, the patient was ultimately diagnosed with Acute Myelomonocytic Leukemia (AMML).

Conclusions: For patients presenting with cervical lymphadenopathy and fever, it is crucial to stabilize the condition while concurrently seeking the underlying cause. Timely completion of relevant examinations, including cervical lymph node biopsy, is essential for definitive diagnosis.