PMC9425876_01
Cytomorphology of bone marrow aspirates. (a) Bone marrow aspirate smear at time of diagnosis (50x magnification) showed subtotal infiltration of myeloid blasts replacing normal hematopoiesis without evidence of myeloid maturation, leading to diagnosis of acute myeloblastic leukemia without maturation according to WHO criteria. (b) Bone marrow aspirate smear at time of relapse (50x magnification) revealed persistence of cytomorphologic remission with a blast count below 5%, myeloid maturation, and normal findings for erythroid and megakaryocytic components. Bone marrow smears (a and b) were stained with the May-Grunwald-Giemsa kit and examined with the Nikon Eclipse E600 microscope. High-resolution pictures were taken with the mounted Nikon DSFi2 camera and processed with the Nikon Imaging Software Elements.
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Bone marrow (BM) aspiration and biopsy confirmed the diagnosis of acute myeloid leukemia (AML) (Figure 1(a)). Surprisingly, BM aspiration showed a persisting CR (Figure 1(b)) without cytogenetic or molecular abnormalities and full donor chimerism.
Overview of the patient's extramedullary AML sites. The patient suffered from multiple extramedullary relapses of different sites (1, mediastinal tumor; 2, duodenal tumor; 3, chloroma; 4, retroperitoneal tumor). The chronology of the occurrence of the EM was as follows: first diagnosis with mediastinal tumor (1), first relapse with duodenal tumor (2), second relapse with chloroma (3), and third relapse with retroperitoneal tumor (4). All EMs were (a) histologically confirmed after EM tissue was obtained by CT-supported biopsy (1 and 4), by duodenoscopy (2), or by punch biopsy (3). Histologic samples were prepared with hematoxylin-eosin staining. Images were captured with the Olympus BX 41TF microscope (magnification 1: 18.7x, 2: 40x, 3: 40x, and 4: 40x) and the 3DHistech Pannoramic Desk. (b) 18FDG-PET/CT imaging revealed mediastinal EM manifestation at diagnosis (b1), duodenoscopy pictured the duodenal tumor (b2), and follow-up 18FDG-PET/MRI depicted the retroperitoneal manifestation (b4). Figure was created with BioRender.
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As the patient complained of chest pain and newly onset of fever episodes, computed tomography (CT) of the thorax was performed on day 6 of DA, depicting a large mediastinal tumor and ground-glass opacities. 18Fluorodesoxy-glucose positron emission tomography/computed tomography (  FDG-PET/CT) demonstrated mediastinal vital tissue [maximum standardized uptake value (SUVmax) 5.3; Figure 2(b1)]. Hence, a biopsy of the tumor was conducted, revealing residual leukemic blasts embedded in necrotic tissue through histologic workup, being the first verified extramedullary site of the patient's AML (Figure 2(a1)). Endoscopy revealed a tumor of the duodenum obstructing the common hepatic duct with the need of stent insertion (Figure 2(b2)). Biopsies were obtained, again demonstrating leukemic infiltration and defining AML relapse (Figure 2(a2)). A punch biopsy verified again leukemic infiltration in this lesion (Figure 2(a3)). Three months later, the patient showed new signs of progression, this time with multiple EMs detected below the left kidney causing urinary obstruction, paravertebrally, and in the coeliac trunk (SUVmax 4, Figure 2(b4)). Again, myelosarcoma was histologically confirmed after biopsy (Figure 2(a4)).