Acute myeloid leukemia with ETV6::CHIC2 fusion gene: 'Pitfalls' in diagnosis.

OBJECTIVES

Acute myeloid leukemia (AML) with ETV6::CHIC2 and basophilia is rare in hematologic malignancies with poor prognosis. Due to the small number of clinical cases, it is misdiagnosed and missed frequently, and it is necessary to explore laboratory detection for accurate diagnosis.

METHODS

We report a case of AML with ETV6::CHIC2 and basophilia by morphological screening, immunotyping with precise gating, interpretation of FISH results, and RNA transcriptome sequencing, thus laying the accurate diagnosis for clinical treatment.

RESULTS

We confirmed a rare case of AML with ETV6::CHIC2 rather than FIP1L1::PDGFRA by morphological analysis, correct immunophenotyping via precise gating, rejecting one-sided view of FISH positive result and targeted RNA sequencing. Precise analysis and more advanced means avoid misdiagnosis and missed frequently. After accurate diagnosis, venetoclax and decitabine therapy were given instead of imatinib; eventually, the patient achieved a relatively good effect.

DISCUSSION: Immunophenotype analysis is necessary to detect the expression of CD7 when encountering pseudo-lymphocytes with multilineage dysplasia and basophilia. FISH and RT-PCR are still indispensable means of diagnosis of fusion genes in hematologic malignancies but can only detect a limited number of known partner genes and fusion genes with known break points. NGS can achieve sequence analysis indiscriminately and detect all fusion transcripts theoretically, greatly improving the detection range. NGS sequencing is required for t(4;12)(q11;p13) in AML that are not accompanied by eosinophilia.