A 25-year-old man presented with fatigue, recurrent episodes of fever and infectious symptoms, night sweats, and inappetence. In addition, dyspnea and chest pain during inspiration were reported. Furthermore, rash on both arms was described. Hematologic workup revealed leukocytosis of undifferentiated cells, which were characterized as myeloid progenitors by immunophenotyping. Bone marrow (BM) aspiration and biopsy confirmed the diagnosis of acute myeloid leukemia (AML) (Figure 1(a)). Cytogenetic analysis revealed an NF1-deletion (del17q11). No other genetic abnormalities were detected using routine molecular analysis methods [fragment length analysis and amplicon-based next generation sequencing (NGS)].
Induction chemotherapy with 60 mg/m2 daunorubicin (day 3-5) and 100 mg/m2 cytarabine (day 1-7) (DA) was initiated. 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)).
BM assessment at day 15 showed moderate response and positive cytogenetic measurable residual disease (MRDpos) with persisting del17q11 detection. A second cycle of DA was initiated leading to cytomorphologic and cytogenetic complete remission (CR). Follow-up CT showed the mediastinal tumor unchanged in diameter. No further extramedullary manifestation (EM) sites were traced in clinical examination and by imaging.
The patient underwent allogeneic hematopoietic cell transplantation (alloHCT) from a matched sibling donor after receiving myeloablative conditioning with 120 mg/kg cyclophosphamide and 12 Gy fractionated total body irradiation (TBI), which was tolerated without unexpected toxicities. Graft versus host disease (GvHD) prophylaxis consisted of methotrexate (MTX) and cyclosporin (CsA). On day +8, the patient reported sudden and severe chest pain again and imaging revealed the mediastinal tumor with unchanged diameters. The patient developed full donor chimerism until day +56 and remained in cytomorphologic and cytogenetic CR. Immunosuppression was tapered rapidly and discontinued 6 months after transplantation.
Eighteen months later, the patient noticed progressive jaundice. Abdominal ultrasound revealed a large tumor of the pancreaticoduodenal region causing cholestasis. 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)). Cytogenetic evaluation of the duodenal tumor was indicative for the known NF1-deletion. In addition, 18FDG-PET/magnetic resonance imaging (MRI) was further suspicious for localized iliac EM (SUVmax 5.4), while the initial mediastinal tumor (SUVmax 3.5-5.2) and the duodenal tumor (SUVmax 3.7) also showed metabolic activity. Surprisingly, BM aspiration showed a persisting CR (Figure 1(b)) without cytogenetic or molecular abnormalities and full donor chimerism. Reinduction with 3000 mg/m2 BID high-dose cytarabine (day 1-3) and 5 mg/m2 mitoxantrone (day 3-5, dose reduction because of pancreatitis) was started, which induced a metabolic CR of the EM according to 18FDG-PET/MRI. At the time of referral to the transplantation ward for second alloHCT, the patient reported about a cutaneous tumor on the chest that rapidly grew within the last few days. A punch biopsy verified again leukemic infiltration in this lesion (Figure 2(a3)). Myeloablative conditioning with 12.8 mg/kg busulfan and 150 mg/m2 fludarabine was applied prior to allografting from an alternative matched unrelated donor (MUD). MTX and CsA were applied as GvHD prophylaxis. Full donor chimerism was achieved again; no further sites of chloroma appeared. BM aspirate revealed persisting CR. The patient developed acute GvHD grade III of the upper and lower gastrointestinal tract and the skin, which required repetitive escalation of immunosuppression. However, a follow-up 18FDG-PET/MRI demonstrated relapse of the mediastinal mass 1 month after the second transplantation (SUVmax 6.6). Local radiation therapy of the mediastinal tumor with a cumulative dose of 40 Gy was conducted leading to a significant shrinking of the mediastinal tumor burden. 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)). Therapy with azacitidine and venetoclax was initiated, resulting in a morphologically complete response after two cycles of chemotherapy as per 18FDG-PET/MRI. To study the clonal landscape of this aggressive and refractory course of extramedullary disease, we performed amplicon-based NGS of AML tumor tissue and compared it with genetic characteristics of the patient's BM AML.