Faggot cells observed in a patient with myelodysplastic syndrome with increased blasts

Excerpt

A 75-year-old woman was referred to our hospital for pancytopenia. An annual blood test performed by her primary care physician 2 months before her visit showed an abnormal blood count (WBC 2880/μL, Hb 10.3 g/dL, and Plt 14.2 × 10⁴/μL). The patient was completely asymptomatic, without any bleeding symptoms. Blood tests conducted at our hospital yielded the following results: WBC 2200/μL (neutrophils 14%, lymphocytes 79%, and monocytes 7%), Hb 8.9 g/dL, Plt 14.5 × 10⁴/μL, LDH 249 IU/L, PT 13.8 s, APTT 26.5 s, fibrinogen 270 mg/dL, and FDP < 5.0 μg/mL. Bone marrow aspiration revealed 11.5% myeloblasts and 3.5% promyelocytes with numerous Auer rods resembling faggot cells of acute promyelocytic leukemia (APL) (Figs. 1a–f). However, neutrophils containing bilobed nuclei with condensed chromatin (Pseudo-Pelger-Huet anomaly), micro-megakaryocytes, and dysplastic erythroblasts were also observed (Figs. 1g–i). Flow cytometry analysis revealed approximately 15% of blasts positive for CD13, CD33, CD34, and HLA-DR, which are atypical for classical APL (Supplementary Material). Polymerase chain reaction testing for PML::RARA yielded negative results, and G-banding and spectral karyotyping revealed the karyotype to be 46,XX,del(6)(q?)[15]/46, XX[5] (Supplementary Material). Based on these findings, myelodysplastic syndrome (MDS) with increased blasts was diagnosed, and azacytidine therapy was initiated. The patient responded to azacytidine and recovered from cytopenia. No faggot cells were observed during follow-up bone marrow aspiration. Although Auer rods are sometimes observed in patients with MDS, only one case of faggot cells in a patient with MDS has been reported, in which the faggot cells were transiently detected during follow-up [1]. This case demanded a careful diagnosis of MDS considering that faggot cells were detected from the initial bone marrow examination. One limitation of our report is that we were unable to test for the specific retinoic acid receptor rearrangement that causes variant APL. Since there were no evident differentiated cells with bundles of Auer rods, we considered two hypotheses: (1) that dysplastic cells and faggot cells (mainly myeloblasts and promyelocytes) were derived from the same clone, and (2) that two different disease-derived clones (i.e., APL and MDS) coexisted in the patient’s bone marrow. Although we could not completely rule out the coexistence of the variant APL with MDS, the absence of coagulopathy and the favorable response to azacytidine monotherapy appear to support our first hypothesis that the faggot cells were arising from MDS clones.

…