Case 294

Submitting Author: Taddesse-Heath, Lekidelu, MD
Institution: Howard University Hospital
Session: Acute leukemias of ambiguous lineage

HISTORY

A 64 year old male who presented with pancytopenia. There was no evidence of organomegaly, lymphadenopathy or skin rashes.

DETAILS

Bone marrow aspirate and core biopsy were obtained. The core biopsy was fixed in formalin. The Wright-Giemsa stained aspirate smear showed greater than 95% blasts. The blasts were mostly large in size with few medium-sized blasts and fewer blasts that were small. The blasts had scant to moderate amount of cytoplasm without any auer rods or granules. The cells had a high nuclear to cytoplasmic ratio, fine chromatin and prominent nucleoli. The nuclei were mostly round with rare cells showing nuclear indentation or folding. The core biopsy showed a hypercellular marrow (90% cellular). The marrow was completely replaced by blasts cells which appear small to medium-sized on the core biopsy.

IMMUNOHISTOCHEMISTRY AND FLOW CYTOMETRY

Immunohistochemical stains showed the following in the blasts:

The majority of the blasts were positive for CD34 and strongly positive for CD43, CD123 and lysozyme. Approximately half of the blasts were positive for TdT and less than half (30-40%) were positive with CD117. A greater number of cells (approximately 20%)stained positively with PAX5 compared to the rare CD19 and CD20 positive cells.

The blasts were essentially negative for CD1a, CD2, CD3, CD5, CD7, CD4, CD8, CD19, CD20, CD79a, CD10, Myeloperoxidase (rare positive cells), CD14 (few positive cells), CD68 and CD163 (histiocytes positive), CD56 and TCL-1.

CYTOGENETIC FINDINGS

Not done

MOLECULAR FINDINGS

Immunoglobulin heavy chain gene rearrangement studies by PCR showed a discreet peak detected in FR2 and FR3 primer sets but no amplification in FR1 primer set.

T cell receptor gene rearrangement studies were attempted but there were no PCR amplified products obtained.

INTERESTING FEATURES

Acute leukemia expressing some lymphoid, myeloid and blastic plasmacytoid dendritic cell neoplasm associated markers but negative for lineage-specific markers.

PROPOSED DIAGNOSIS

Acute leukemia of ambiguous lineage, acute undifferentiated leukemia

CONSENSUS DIAGNOSIS

Acute myeloid leukemia with monocytic differentiation