This report describes a newly diagnosed case of acute myeloid leukemia (AML) in which peripheral blood morphology demonstrated an atypical, dimorphic population of blasts. The manuscript is presented as a case report in J Hematop (2026 Aug 22;19[1]:49) by Christopher Vossen and Clarissa E Jordan of the Division of Hematopathology, Mayo Clinic. The record is indexed in PubMed (PMID 42629503) and published with DOI 10.1007/s12308-026-00726-1.
The authors highlight a diagnostic scenario in which morphologic assessment alone could be misleading and emphasize the role of ancillary testing. Declarations in the publication note no funding, no competing interests, and that the Mayo Clinic IRB considered the activity not to require IRB review under 45 CFR 46.102. The article lists keywords including Acute myeloid leukemia, Flow cytometry, and Mature lymphoid morphology.
Peripheral blood smear evaluation revealed a dimorphic blast population. One subset of blasts had morphology consistent with typical myeloblasts. A second, morphologically distinct subset displayed features resembling mature lymphoid cells, an unusual appearance for myeloid blasts. The authors characterize this appearance as "mature lymphoid‑like morphology."
The presence of two discrete morphologic subsets created a potential diagnostic pitfall: the lymphoid‑like subset could be mistaken for a separate lymphoid neoplasm or a coincident lymphoproliferative disorder if interpretation relied on morphology alone.
To resolve the morphologic ambiguity, flow cytometric immunophenotyping was performed. Immunophenotyping was crucial in this case: flow cytometry demonstrated that both the typical myeloblasts and the lymphoid‑appearing subset belonged to a single myeloid blast population rather than representing two distinct hematologic lineages.
The report underscores that immunophenotypic data can identify lineage and maturation stage when morphology is atypical or misleading. While the abstract and record emphasize the importance of flow cytometry in characterizing the dimorphic population, specific antigen panels, marker expression patterns, or flow data values were not reported in the PubMed abstract.
This case exemplifies a recognized diagnostic pitfall in hematopathology: abnormal myeloblasts may mimic lymphoid cells by chromatin pattern, cytoplasmic features, or overall cell size and shape. The authors reference prior reports in the literature addressing similar scenarios where myeloblasts showed abnormal chromatin clumping or otherwise resembled chronic lymphoid disorders, highlighting that "appearances can be deceptive."
The central message is that reliance on morphology alone risks misclassification. Integration of peripheral smear review with flow cytometry and other immunophenotypic techniques is essential to establish lineage and avoid diagnostic error.
Clinically and for laboratory workflow, this report reinforces several practical points:
Unusual blast morphology should prompt reflex or early immunophenotypic testing rather than definitive lineage assignment solely by microscopy.
Flow cytometry can consolidate morphologically disparate cell populations into a single diagnostic entity when immunophenotype is concordant.
Awareness of morphologic mimicry reduces risk of misdiagnosis and inappropriate downstream management that could follow a mistaken lymphoid versus myeloid classification.
Specific therapeutic, prognostic, or management implications were not detailed in the PubMed abstract; the report focuses on the diagnostic process and the role of ancillary testing.
This item is a case report and includes declarations that the study received no funding and that the authors declare no competing interests. According to the record, the Mayo Clinic Institutional Review Board determined that the described activity did not require IRB review per 45 CFR 46.102, and informed consent and consent for publication were not required for this type of study.
The article cites prior literature addressing AML cases with lymphoid‑mimicking morphology, chromatin clumping in myeloblasts, and related diagnostic pitfalls. Full methodological details, detailed flow cytometry panels, and numeric data were not provided in the PubMed abstract; readers interested in those specifics should consult the full text of the published report (DOI 10.1007/s12308-026-00726-1).
References cited in the PubMed record include prior case reports and brief communications on AML mimicking mature lymphoid morphology and related phenomena, demonstrating that this diagnostic challenge has precedent in the hematopathology literature.