|LETTER TO EDITOR
|Year : 2020 | Volume
| Issue : 3 | Page : 624-626
Extramedullary hematopoiesis: Detection of common and rare sites of involvement using18F-fluorodeoxyglucose and18F-fluorothymidine positron emission tomography–computed tomography scan
Melvika Pereira, Nilendu Purandare, Ameya D Puranik, Sneha Shah, Archi Agrawal, Venkatesh Rangarajan
Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, HBNI, Mumbai, Maharashtra, India
|Date of Submission||24-Feb-2020|
|Date of Decision||23-Mar-2020|
|Date of Acceptance||26-Mar-2020|
|Date of Web Publication||19-Sep-2020|
Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, E. Borges Road, Parel, Mumbai - 400 012, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pereira M, Purandare N, Puranik AD, Shah S, Agrawal A, Rangarajan V. Extramedullary hematopoiesis: Detection of common and rare sites of involvement using18F-fluorodeoxyglucose and18F-fluorothymidine positron emission tomography–computed tomography scan. Cancer Res Stat Treat 2020;3:624-6
|How to cite this URL:|
Pereira M, Purandare N, Puranik AD, Shah S, Agrawal A, Rangarajan V. Extramedullary hematopoiesis: Detection of common and rare sites of involvement using18F-fluorodeoxyglucose and18F-fluorothymidine positron emission tomography–computed tomography scan. Cancer Res Stat Treat [serial online] 2020 [cited 2020 Oct 25];3:624-6. Available from: https://www.crstonline.com/text.asp?2020/3/3/624/295523
Extramedullary hematopoiesis (EMH) is the occurrence of hematopoietic tissue in sites other than bone marrow such as liver, spleen, and dorsal paraspinal region, when the primary sites of medullary hematopoiesis in adults fail (in myelofibrosis, hemoglobinopathies, and rare cases of malignant solid tumors)., In rare cases, organ involvement is seen and can be confused for neoplastic process on imaging.
A 44-year-old man with no comorbidities presented with complaints of generalized weakness, fatigue for over 3 months, and breathlessness on exertion. He gave no history of fever or bony pains. There was no palpable hepatosplenomegaly or adenopathy. Blood examination showed hemoglobin: 7.5 g/dL, white blood cell: 4.07 × 109/L, platelet: 243 × 109/L; serum creatinine: 0.5 mg/dL, lactate dehydrogenase: 127 U/L, and total bilirubin: 2.7 mg/dL. On peripheral blood smear, red blood cells show microcytosis, anisocytosis, hypochromia, and anisochromia. Ultrasonography of the abdomen detected a round hypoechoic mass in the right renal pelvis. Computed tomography (CT) scan revealed soft tissue masses in the presacral region, posterior mediastinum with right pleural effusion, and an enhancing well-defined mass in the right renal medulla. The patient was referred to our hospital for18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography (PET)-CT scan [Figure 1]a and further workup due to a clinicoradiological suspicion of lymphoma. Scan findings revealed a thoracic paravertebral bilateral lobulated mass, with no isthmus between the two masses, smoothly marginated heterogeneously enhancing, CT attenuation similar to that of the adjacent muscle, with focal areas of fat attenuation, no bony erosion, or calcifications [Figure 1]b. Another presacral homogeneously enhancing soft tissue mass with smooth margins was detected [Figure 1]d. Most unusual finding was a well-defined enhancing soft tissue mass in the right renal medulla, abutting the renal pelvis [Figure 1]c. All three lesions demonstrated low-grade FDG tracer concentration. Diffuse sclerosis was noted in the pelvic bones, bilateral proximal femur, and few vertebrae without hepatosplenomegaly.
|Figure 1: A 44-year-old man, case of extramedullary hematopoiesis18F-fluorodeoxyglucose positron emission tomography-contrast-enhanced computed tomography fused whole-body (a) and transaxial images (b-d) showing heterogeneous low-grade tracer localization in three masses noted with arrowheads, (b) bilateral dorsal paravertebral lobulated mass, (c) an unusual parapelvic soft tissue mass in right renal pelvis, and (d) presacral soft tissue mass. No adjacent bony erosion seen|
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Although presacral and thoracic paraspinal locations are known sites of EMH after liver and spleen, other differential diagnoses include neurogenic tumors, lymphoma, and extramedullary myeloid sarcoma, which can often have a similar appearance.,, As in our case, CT findings showed bilateral paravertebral masses with no soft tissue connection between the two masses (unlike in lymphoma) and no osseous erosion (unlike in neurogenic tumors). Low FDG tracer concentration in all lesions was a characteristic which helped distinguish it from most types of lymphoma and extramedullary myeloid sarcoma demonstrating increased FDG uptake. Thus, 18F-FDG PET-CT helped strengthen our radiological suspicion for EMH.
Renal pelvic mass raised possible differentials of EMH, low-grade lymphoma, or primary renal malignancy. EMH sites being highly vascular, renal biopsy would be invasive with fear of bleeding and other complications. Hence, we performed noninvasive bone marrow imaging with18 F-fluorothymidine (18 F-FLT) PET-CT and 99mTc sulfur colloid (SC) scintigraphy to corroborate the FDG PET-CT findings. 99mTc SC planar/single-photon emission computed tomography (SPECT)-CT imaging and 18F-FLT PET/CT scan [Figure 2] revealed heterogeneous increased tracer localization in the paraspinal thoracic, presacral, and right renal medullary lesions, with diffuse nonuniform tracer uptake in the marrow, further supporting our diagnosis.
|Figure 2: Bone marrow scintigraphy in the same patient to confirm extramedullary hematopoiesis in the unusual sites of right renal pelvis. Whole-body images of (a)18F-fluorothymidine positron emission tomography-computed tomography and (b) 99m Tc – sulfur colloid single-photon emission computed tomography-computed tomography images showed tracer localization in dorsal paravertebral and presacral mass and right renal parapelvic mass|
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CT-guided biopsy from paraspinal thoracic mass reviewed at our institution revealed marrow tissue comprising megakaryocytes, erythroid cells, and myeloid cells. Immunohistochemistry for glycoprotein confirmed the presence of erythroid cells. C-kit and CD34 stains were negative; findings compatible with EMH. Bone marrow biopsy was normocellular with grade 1 fibrosis, hyperplasia in erythroid series, megaloblastic change, and reduced myeloid series. ASXL1 gene mutation was positive in this patient, which led us to the cause of EMH: primary myelofibrosis (mutation positive in 36%). [Figure 3] displays the timeline of previous and current information in our patient.
A rare presentation in EMH is the renal involvement as a solitary mass, which can involve the cortex, medulla, pelvis, or perirenal region, and on imaging, it may mimic lymphoma, tumor, inflammatory, or infectious etiology. Pelvicalyceal or hilar involvement like in our case is often an extension of a parenchymal lesion pattern, with possibility of obstructive renal failure, but more commonly is asymptomatic. Atypical imaging features with no underlying hematopoietic disorder to suggest a diagnosis of EMH affect clinical decision-making and histological validation is required. However, since biopsy is risky and at times inaccessible, noninvasive imaging procedures are required to help determine the nature of the tissue. 18F-FDG PET-CT scan can help detect the common as well as rare sites of EMH, to rule out other possible differential diagnoses based on characteristic low-to-moderate FDG tracer concentration and classic imaging features such as heterogeneous, fat-containing, soft tissue masses. DNA precursor 18F-FLT shows increased uptake in highly proliferating tumors/cells. 18F-FLT PET can thus help visualize proliferative activity of the bone marrow compartment in hematological disorders and could be used for monitoring/response evaluation.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]