High-dose methotrexate (HD-MTX) is a key drug in the treatment of various cancers. Massive fluid infusion is necessary during HD-MTX therapy to ensure proper methotrexate excretion. There are no reports on the safety of HD-MTX therapy in patients with congenital solitary kidney (CSK). A 5-year-old male child with CSK and B-cell precursor acute lymphoblastic leukemia was treated with four cycles of HD-MTX therapy. HD-MTX therapy was safely administered without delayed MTX excretion or renal dysfunction. This case showed that HD-MTX therapy was well tolerated by a pediatric patient with CSK.

Pediatric erythroblastic transformation of JAK 2-mutated prefibrotic primary myelofibrosis with concurrent PHF6 mutationsTokiko Oshiro1, Satoru Hamada1, Sinobu Kiyuna1, Hideki Sakiyama1, Nobuyuki Hyakuna2, Tomoko Tamaki3, Hideki Muramatsu4, Koichi Nakanishi5Department of Pediatrics, University of Ryukyus HospitalOkinawa prefectural Red Cross Blood CenterDepartment of Pathology and Oncology, Graduate school of Medicine, University of RyukyusDepartment of Pediatrics, Graduate School of Medicine, University of NagoyaDepartment of Pediatrics, Graduate School of Medicine, University of The RyukyusCorrespondence: Satoru Hamada,Department of Pediatrics, Faculty of Medicine, University of Ryukyus, 207 Uehara, Nishihara-cho, Okinawa 903-0125, [email protected] the Editor: Primary myelofibrosis (PMF) is a rare condition in children. According to the 2016 World Health Organization (WHO), classification of myeloproliferative neoplasms (MPN), PMF is divided into prefibrotic PMF (pre-PMF) and overt fibrotic PMF1. Pre-PMF is the proliferation of predominantly abnormal megakaryocytes and minimal or no reticulin fibrosis. Therefore, the lack of fibrosis in the early phase of thrombocytosis can be misdiagnosed as essential thrombocythemia2. One significant complication of MPN is leukemic transformation (LT); however, only a few cases of PMF in children have been reported3. The clinical utility of the three driver mutations in JAK2 , CALR, and MPL has been shown, especially when JAK2 is central to the pathogenesis of the MPN phenotype4. Additional mutations in ASXL1, SRSF2, IDH1/2, or EZH2 have been shown5. PHF6is an X-linked tumor suppressor gene with a somatic mutation that causes an aggressive type of myeloid neoplasm6. Here, we report a case of pediatricJAK2 -mutated pre-PMF with concurrent PHF6 mutations that transformed into AML within a year of diagnosis.A 14-year-old boy with no medical history was admitted to our hospital with lumbago. Physical examination revealed splenomegaly (5 cm below the costal margins). A complete blood count showed a white blood cell (WBC) count of 5.8×109/L, neutrophil count of 31%, lymphocyte count of 36%, red blood cell count of 7.34×109/L, hemoglobin concentration of 140 g/L, and platelet count of 1010×109/L. The patient was diagnosed with essential thrombocythemia based on bone marrow findings, which showed hypercellularity (80-100%), increasing with separated circled-multinucleated megakaryocytes, hyper-segmented-megakaryocytes, atypical megakaryocytes, and micromegakaryocytes (Figure 1A), and was treated with anagrelide. At this time, there were no blasts or reticulin fibers. The patient had no karyotypic abnormalities. After written informed consent was obtained, target capture-based next generation sequencing (NGS) was performed on bone marrow DNA for the following genes: MPL, ASXL1, CBL, JAK3, EZH2, IDH1, IDH2, JAK1, PHF6, SF 3B1, TET2, TP53, U2AF1, JAK2, NRAS/KRAS and IKZF1 by previous described methods7. Among these mutations, JAK2 V617F with mutant allele percentage 4% and PHF6 p.Q121Xmutation with 64% were identified. In addition, we generated an MPN gene panel (JAK2 V617F, JAK2 exon12, MPL W515L, MPL W515K, CALR type1-5 ) using DNA microarray methods (SRL International Inc. Japan) and only the JAK2V617F mutation was identified. As the platelet count decreased, his symptoms became well-controlled. However, teardrop-shaped red blood cells and myeloblasts were observed in the peripheral blood six months later, and we performed a bone marrow biopsy. Results indicated hypercellularity (80-100%) with moderate fibrosis (MF grade 1; Figure 1B). Therefore, ruxolitinib was administered for myelofibrosis. Five months later, he showed elevated lactate dehydrogenase (LDH) levels and thrombocytopenia. Bone marrow aspiration revealed increased cellularity with predominant erythropoiesis and 40% erythroblasts (Figure 1C). Flow cytometric analyses revealed 14% glycophorin A and 90% CD34 positive blast cells. No reticulin fibrosis progression was observed. The cytogenetic analysis revealed a normal karyotype. The patient was diagnosed with acute erythroleukemia secondary to PMF. He underwent HLA haploidentical peripheral blood stem cell transplantation(haplo-HCT) from his mother, using post-transplantation cyclophosphamide (PT-Cy) for graft-versus-host disease (GVHD) prophylaxis. The conditioning regimen consisted of total body irradiation (12 Gy delivered in six fractions from days -8 to -6), fludarabine (30mg/m2 from days -5 to -2), and cytarabine (3,000 mg/m2×2 from days -5 to -4). GVHD prophylaxis consisted of high-dose PT-Cy (50 mg/kg intravenously on days 3 and 4) in combination with tacrolimus and mycophenolate mofetil from day 5 onward. Infused donor cells were 5.4×106/kg CD34 cells and 4.0×108/kg CD3 positive T cells. Engraftment occurred on day 21, and complete chimerism was achieved on day 33. He had several transplantation-related complications, including grade II acute GVHD (gut), which was treated with prednisolone; BK virus-associated hemorrhagic cystitis; and bronchiolitis obliterans syndrome (Supplementary Figure). He has been in complete remission for 7 years after transplantation. Considering that the bone marrow features are characterized by increasing cellularity with atypical megakaryocytes at clinical onset, the patient should first be diagnosed with pre-PMF.Our patient developed AML (FAB M6) 11 months after the diagnosis of pre-PMF. In terms of time to progression, median time (range) to progression was 11.8 years (7.9-15.7 years) in pre-PMF8. According to the Dynamic International Prognostic Scoring System (DIPSS) Plus score, our case was classified as low-risk. Candidate genes contributing to LT from MPN to AML have been identified, including TP53, TET2, ASXL1, EZH2, IDH1/2, RUNX1, U2AF1, NRAS/KRAS , and SRSF2 5. The adverse impact of molecular characteristics on survival in pre-PMF and overt PMF has been reported as a high mutation risk in EZH2, ASXL1, IDH1, IDH2 , and SRSF2 8. In our case, no additional somatic alterations were detected; however, a PHF6 mutation was identified. Somatic PHF6 mutations have been found in 2–3% of AML6, 9. The percentage of blasts in the bone marrow tends to be higher in patients with myeloid malignancies harboringPHF6 mutations6. AML with high PHF6expression levels than controls correlated with shorter overall survival10. Furthermore, increased PHF6 levels may be associated with CD34 positivity10. In a case series of MPN with increased fibrosis and blast crisis, 22 patients withPHF6 mutations in MPN were enriched11. Thus,PHF 6 mutations can contribute to myeloid leukemic transformation in JAK2 -mutated pre-PMF.AcknowledgementsWe are grateful to our patients and his family. And we would like to thank our colleagues for helpful discussion regarding this case.Conflict-of-interestThe authors declare that there is no conflict of interest.【References】(1) Tefferi A. Primary myelofibrosis: 2017 update on diagnosis, risk-stratification, and management. Am J Hematol. 2016;91(12):1262-1271.(2) Edahiro Y, Araki M, Inano T, Ito M, Morishita S, Misawa K, Fukuda Y, Imai M, Ohsaka A, Komatsu N. Clinical and molecular features of patients with prefibrotic primary myelofibrosis previously diagnosed as having essential thrombocythemia in Japan. Eur J Haematol. 2019;102(6):516-520.(3) DeLario MR, Sheehan AM, Ataya R, Bertuch AA, Vega C, Webb CR, Lopez-Terrada D, Venkateswaran L. Clinical, histopathologic, and genetic features of pediatric primary myelofibrosis–an entity different from adults. Am J Hematol. 2012;87(5):461-464.(4) Nangalia J, Green TR. The evolving genomic landscape of myeloproliferative neoplasms. Hematology Am Soc Hematol Educ Program. 2014;2014(1):287-296.(5) Andrew J. Dunbar, Raajit K. Rampal, Ross Levine; Leukemia secondary to myeloproliferative neoplasms. Blood 2020;136(1):61–70.(6) Mori T, Nagata Y, Makishima H, Sanada M, Shiozawa Y, Kon A, Yoshizato T, Sato-Otsubo A, Kataoka K, Shiraishi Y, Chiba K, Tanaka H, Ishiyama K, Miyawaki S, Mori H, Nakamaki T, Kihara R, Kiyoi H, Koeffler HP, Shih LY, Miyano S, Naoe T, Haferlach C, Kern W, Haferlach T, Ogawa S, Yoshida K. Somatic PHF6 mutations in 1760 cases with various myeloid neoplasms. Leukemia. 2016;30(11):2270-2273.(7) Muramatsu H, Okuno Y, Yoshida K, Shiraishi Y, Doisaki S, Narita A, Sakaguchi H, Kawashima N, Wang X, Xu Y, Chiba K, Tanaka H, Hama A, Sanada M, Takahashi Y, Kanno H, Yamaguchi H, Ohga S, Manabe A, Harigae H, Kunishima S, Ishii E, Kobayashi M, Koike K, Watanabe K, Ito E, Takata M, Yabe M, Ogawa S, Miyano S, Kojima S. Clinical utility of next-generation sequencing for inherited bone marrow failure syndromes. Genet Med. 2017;19(7):796-802.(8) Guglielmelli P, Pacilli A, Rotunno G, Rumi E, Rosti V, Delaini F, Maffioli M, Fanelli T, Pancrazzi A, Pietra D, Salmoiraghi S, Mannarelli C, Franci A, Paoli C, Rambaldi A, Passamonti F, Barosi G, Barbui T, Cazzola M, Vannucchi AM; AGIMM Group. Presentation and outcome of patients with 2016 WHO diagnosis of prefibrotic and overt primary myelofibrosis. Blood. 2017;129(24):3227-3236.(9) de Rooij JD, van den Heuvel-Eibrink MM, van de Rijdt NK, Verboon LJ, de Haas V, Trka J, Baruchel A, Reinhardt D, Pieters R, Fornerod M, Zwaan CM. PHF6 mutations in paediatric acute myeloid leukaemia. Br J Haematol. 2016;175(5):967-971.(10) Mousa NO, Gado M, Assem MM, Dawood KM, Osman A. Expression profiling of some Acute Myeloid Leukemia - associated markers to assess their diagnostic/prognostic potential. Genet Mol Biol. 2021;44(1):e20190268.(11) Kurzer JH, Weinberg OK. PHF6 Mutations in Hematologic Malignancies. Front Oncol. 2021;11:704471.Figure legendsFigure 1A. Bone marrow aspiration at first visit(day-370).Square (A) shows a separated circular multinucleated megakaryocyte, (B) a hypersegmented megakaryocyte, (C) an atypical megakaryocyte, and (D) a micromegakaryocyte.Figure 1B. Bone marrow biopsy on day-170.Silver impregnation shows moderate myelofibrosis. Arrows indicate reticulin fibers.Figure 1C. Bone marrow smear (1000×, May-Grunwald-Giemsa stain). The smear shows abnormal megakaryoblasts with round or oval nuclei, loose chromatin, agranular cytoplasm with blebs.Supplemental Figure 1. Clinical course of patients.A bone marrow biopsy on day-170 shows myelofibrosis, and bone marrow aspiration on day-30 shows erythroleukemia. aGVHD, acute graft-versus host disease; PSL, prednisolone; TBI, total body irradiation; FLU, fludarabine; Ara-C, cytarabine; CY, cyclophosphamide; MMF, mycophenolate mofetil; Haplo-SCT, haploidentical stem cell transplantation; BMA, bone marrow aspiration; BMB, bone marrow biopsy; BM, bone marrow.

Juxtaglomerular cell tumor with pulmonary metastases: A case report and review of the literatureHideki Sakiyama1, Satoru Hamada1,2, Tokiko Oshiro1,2, Nobuyuki Hyakuna1,2 Masaaki Kuda3, Tomoro Hishiki4, Hajime Aoyama5, Naoto Kuroda6, Kenji Yorita7, Naoki Wada8, Takako Yoshioka9, Yuhki Koga10, Koichi Nakanishi1,21) Department of Pediatrics, University of the Ryukyus Hospital, Uehara, Nishihara, Okinawa, Japan2) Department of Child Health and Welfare, Graduate School of Medicine, University of the Ryukyus, Uehara, Nishihara, Okinawa, Japan3) Department of Digestive and General Surgery Graduate School of Medicine, University of the Ryukyus, Uehara, Nishihara, Okinawa, Japan4) Department of Pediatric Surgery, Chiba University Graduate School of Medicine, Chiba, Japan5) Department of Pathology, Heartlife Hospital, Okinawa, Japan6) Department of Internal Medicine, Kinro Hospital, Kochi, Japan7) Department of Diagnostic Pathology, Japanese Red Cross Kochi Hospital, Kochi, Japan8) Department of Pathology and Oncology, Graduate School of Medicine, University of Ryukyus, Uehara, Nishihara, Okinawa, Japan9) Department of Pathology, National Center for Child Health and Development, Tokyo, Japan10) Department of Pediatrics, Graduate School of Medical Science, Kyusyu University, Fukuoka, JapanCorrespondence: Satoru Hamada,Department of Pediatrics, Faculty of Medicine, University of Ryukyus, 207 Uehara, Nishihara-cho, Okinawa 903-0125, [email protected] the Editor: Juxtaglomerular cell tumor (JGT) is a relatively rare, benign renin-producing tumor that causes hypertension, hyperaldosteronism, and hypokalemia due to excessive renin secretion. Here, we report a case of malignant JGT with pulmonary metastases. A 7-year-old male patient was referred to the hospital for proteinuria found during a school medical checkup. An ultrasound examination revealed a tumor on the right kidney. His blood pressure was 170/120 mmHg, and plasma renin activity was high at 30 ng/mL/hr. Computed tomography (CT) revealed a mass of 3.4 cm diameter on the right kidney with multiple pulmonary metastases, which was suggestive of nephroblastoma. He underwent right nephrectomy, resulting in a return of blood pressure and plasma renin activity to normal levels (reference range, 0.2–2.3 ng/mL/hr). Gross examination of the tumor revealed a 3.2 × 3.2 × 10-cm yellowish-white mass with necrosis in the mid pole of the kidney. Most of the tumor was covered with a fibrous membrane that partially extended into the normal tissue. Histology revealed a mesenchymal neoplasm with a blastemal component that was suggestive of nephroblastoma. No vascular invasion was observed within the analyzed area (Supplemental Figures S1, S2). Subsequently, he received chemotherapy according to the DD-4A regimen of the National Wilms Tumor Study Group. The immunophenotype demonstrated renin and CD34 positivity (Supplemental Figures S3, S4). This led to a definitive diagnosis of JGT, which was consistent with the clinical feature of hypertension. Chemotherapy was stopped at week 6, at which point CT revealed unchanged metastatic lung lesions. He then underwent a two-stage surgical resection for bilateral lung metastases, and total resection was achieved. Pathologically, the metastatic lung lesions were consistent with the resected renal tumor. Because no reports of effective chemotherapy for malignant JGT were found, we followed-up this patient without administering adjuvant chemotherapy. He showed no evidence of disease after a 2-year follow-up. Targeted DNA sequencing using FoundationOne® CDx detected six genetic mutations:NOTCH3 T272M, BRAF D22N, MAP3K1 L78P, CDKN2BA56D, DAXX E451del, and ERBB4 P3L in the primary tumor.JGT is a rare benign tumor that is more common in relatively young adults. JGT causes various clinical symptoms, such as headache, nausea, dizziness, weakness, hypertension, and proteinuria.1,2JGT is generally curable by surgical resection, and tumor removal results in the improvement of hyperreninemia and clinical symptoms.1 Immunohistochemically, the diagnosis is confirmed by renin positivity in the cytoplasm. In addition, CD34, CD117, vimentin, and ACTA2 are often positive.2,3Although JGT is generally considered benign, eight malignant or pathologically atypical cases have been reported in the literature (Table).3–10 Six were adult cases, and one was a pediatric case. In all cases, the tumor diameter was relatively large (>5 cm). Pathologically, seven of eight showed either vascular invasion or mitotic figures, and among these cases, four had distant metastasis: case 1 demonstrated bilateral lung metastases 6 years after nephrectomy,4 case 4 demonstrated bilateral lung metastases at initial diagnosis,9 case 6 demonstrated multicentric synchronous disease in the liver and spleen,7 case 8 succumbed to hepatic and bone metastases 10 months after nephrectomy.3 In our case, complete metastasectomy of the bilateral pulmonary nodules was achieved after nephrectomy. Thus, he was in remission at 2 years without adjuvant chemotherapy.Ours is the first reported case of pediatric malignant JGT with multiple pulmonary metastases. Although most patients with malignant JGT present with a large tumor that is pathologically characterized by vascular invasion, our case had a relatively small-sized tumor with no vascular invasion or nuclear atypia. Few reports have described genetic abnormalities in JGT. Targeted DNA sequences in our case revealed six gene mutations although the significance of these mutations in the pathogenesis of malignant JGT is unclear. A previous study reported that the NOTCH3 receptor is highly expressed in reninoma in mice.11 Dysregulation of NOTCH3 signaling plays a role in soft tissue tumor pathogenesis.12 Therefore, the NOTCH3 mutation in our case might have been involved in this malignant transformation. In addition, NOTCH3 signaling has shown to contributed to chemoresistance to doxorubicin13, which was consistence with the clinical feature of an ineffective for metastatic lung lesions after chemotherapy including doxorubicin. JGT is generally considered to be a benign tumor, but malignant cases have recently been reported. Our patient was successfully treated with complete pulmonary metastasectomy after primary tumor resection without adjuvant chemotherapy. Pulmonary metastasectomy represents an effective approach in the treatment of JGT-related lung metastases alone. However, no established reports on the prognosis and treatment of malignant JGT exist; thus, additional case reports are needed.Conflict of Interest StatementThe authors declare that there is no conflict of interest.1. McVicar M, Carman C, Chandra M, Abbi RJ, Teichberg S, Kahn E. Hypertension secondary to renin-secreting juxtaglomerular cell tumor: case report and review of 38 cases. Pediatr Nephrol 1993;7:404-412.2. Kuroda N, Gotoda H, Ohe C, et al. Review of juxtaglomerular cell tumor with focus on pathobiological aspect. Diagn Pathol 2011;6:80.3. Zhou J, Zheng S, Zhang Y, et al. Juxtaglomerular cell tumor: clinicopathologic evaluation in a large series emphasizing its broad histologic spectrum. Pathol Int 2020;70:844-856.4. Duan X, Bruneval P, Hammadeh R, et al. Metastatic juxtaglomerular cell tumor in a 52-year-old man. Am J Surg Pathol 2004;28:1098-1102.5. Beaudoin J, Périgny M, Têtu B, Lebel M. A patient with a juxtaglomerular cell tumor with histological vascular invasion. Nat Clin Pract Nephrol 2008;4:458-462.6. Shera AH, Baba AA, Bakshi IH, Lone IA. Recurrent malignant juxtaglomerular cell tumor: a rare cause of malignant hypertension in a child. J Indian Assoc Pediatr Surg 2011;16:152-154.7. Cucchiari D, Bertuzzi A, Colombo P, et al. Juxtaglomerular cell tumor: multicentric synchronous disease associated with paraneoplastic syndrome. J Clin Oncol 2013;31:e240-e242.8. Munakata S, Tomiyama E, Takayama H. Case report of atypical juxtaglomerular cell tumor. Case Rep Pathol 2018;2018:6407360.9. Huang PW, Lin YC, Wu KF, Sheng TW, Su PJ. Juxtaglomerular cell tumor with lung metastases in a young male patient. J Cancer Surviv . 2019;6(3):128.10. Hagiya A, Zhou M, Hung A, Aron M. Juxtaglomerular cell tumor with atypical pathological features: report of a case and review of literature. Int J Surg Pathol 2020;28:87-91.11. Martini AG, Xa LK, Lacombe M-J, et al. Transcriptome analysis of human reninomas as an approach to understanding juxtaglomerular cell biology. Hypertension 2017;69:1145-1155.12. Raimondi L, Ciarapica R, De Salvo M. Inhibition of Notch3 signalling induces rhabdomyosarcoma cell differentiation promoting p38 phosphorylation and p21(Cip1) expression and hampers tumour cell growth in vitro and in vivo. Cell Death Differ 2012;19:871-881.13. Xiu M, Wang Y, Li B, et al. The Role of Notch3 Signaling in Cancer Stemness and Chemoresistance: Molecular Mechanisms and Targeting Strategies. Front Mol Biosci. 2021;14:694141.Figure legendsFigure S1. Neoplastic cells with an ovoid shape proliferate in a solid sheet growth pattern, 40×.Figure S2. Neoplastic cells display rare mitotic activity and mild nuclear atypia, 200×.Figure S3. Neoplastic cells show CD34 labeling, 200×.Figure S4. Renin is diffusely distributed in the tumor cytoplasm, 200×.

Poor graft function (PGF) is a major obstacle to successful allogeneic stem cell transplantation after achieving normal bone marrow function. We report a successful treatment of domino DLI for poor graft function in younger brother with hyper IgM syndrome from HLA-identical elder brother with the same disorder with a history of HLA-mismatched unrelated bone marrow transplantation using same donor. Immunological profiling revealed that DLI-induced T-regulatory cells could correct skewed immune responses in the BM microenvironment due to secondary PGF pathogenesis. Immunological tolerized domino DLI can be a new therapeutic option for secondary PGF in HLA-identical sibling pairs with congenital immunodeficiency.