#00065423

An 80-year-old woman was diagnosed with acute myeloid leukemia (AML). Bone marrow aspirate revealed increased large-sized myeloblasts with scant cytoplasm, irregular nuclei, and fine chromatin. Some blasts contained cytoplasmic vacuoles with engulfed red blood cells, consistent with erythrophagocytosis (see yellow arrows; Wright-Giemsa stain, original magnification ×100 for all panels). The myeloblasts had high side scatter, and were positive for CD4, CD11b(dim), CD11c, CD13 (negative to dim), CD14 (minor subset), CD15, CD33, CD56(partial), CD64, HLA-DR, and myeloperoxidase and negative for CD34 and CD117. Next-generation sequencing identified 3 different tier 1 mutations of TET2 with variant frequencies of 37%, 22%, and 6%. Chromosome analysis showed a complex karyotype: 45∼47,XX,add(3)(q29),+5,i(5)(p10),t(8;22)(p11.2;q13),der(10;15)(q10;q10),der(10;18) (q10;q10),der(10;21)(q10;q10),der(10;22)(q10;q10),+13,der(19)t(11;19)(q13;p13.3)del(11) (q23q23),+mar[cp19]/46,XX[1]. Translocations t(8;22)(p11;q13) involving KAT6A (lysine histone acetyltransferase 6A) and EP300 have been reported in rare cases of acute monocytic leukemia or acute myelomonocytic leukemia.

KAT6A is a member of the MYST family of histone acetyltransferases. AML with KAT6A translocation is very rare (<0.5% of AML), with CREBBP the most common partner, followed by TIF2 and EP300. The majority of AML cases with KAT6A translocations are therapy-related, with poor prognosis. Our case demonstrates the unique features of myeloblasts with KAT6A translocation, including monocytic differentiation without immature marker expression (CD34 and CD117) and erythrophagocytosis.

For additional images, visit the ASH Image Bank, a reference and teaching tool that is continually updated with new atlas and case study images. For more information, visit https://imagebank.hematology.org.