Iron-containing pathologies of the spleen: magnetic resonance imaging features with pathologic correlation
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REVIEW
Iron‑containing pathologies of the spleen: magnetic resonance imaging features with pathologic correlation Nikita Consul1 · Sidra Javed‑Tayyab2 · Ajaykumar C. Morani3 · Christine O. Menias4 · Meghan G. Lubner5 · Khaled M. Elsayes4,6 Received: 18 May 2020 / Revised: 17 July 2020 / Accepted: 25 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Systemic and non-systemic pathologies that involve iron deposition within the spleen have characteristic features on MRI due to the susceptibility properties of deposited iron, or hemosiderin. These lesions will have signal loss on longer echo sequences due to the T2* effect when evaluated with dual-echo gradient-echo sequences. The pathophysiology of systemic and localized iron sequestration disease processes can elucidate an underlying diagnosis based on these imaging features in conjunction with clinical information. Keywords Hemosiderin · Spleen · MRI · Iron deposition · Superparamagnetic · T2* effect
Introduction Iron is incorporated into hemoglobin and used for aerobic respiration and erythropoiesis. Many physiological processes are present to ensure iron homeostasis [1]. However, iron is toxic to cells in its free form and therefore must be stored in tissues such as the bone marrow, liver, and spleen in various forms, among which the most common include ferritin, transferrin, and hemosiderin [1, 2]. Normally or in a state of clinical iron deficiency, the amount of iron contained within ferritin is higher than iron contained within hemosiderin because ferritin is a soluble iron-containing protein that * Khaled M. Elsayes [email protected] 1
Department of Diagnostic Radiology, Baylor College of Medicine, Houston, TX 77030, USA
2
Department of Radiology, Memorial-Sloan Kettering Cancer Center, New York, NY 10065, USA
3
Department of Abdominal Imaging, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
4
Department of Diagnostic Radiology, Mayo Clinic, Scottsdale, AZ, USA
5
Department of Radiology, University of Wisconsin School of Medicine & Public Health, Madison, WI 53726, USA
6
Department of Radiology, Unit 1473, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, TX 77030, USA
can be easily mobilized. Pathologic iron overload leads to an accumulation of serum ferritin and then long-term storage in the form of hemosiderin occurs when iron is deposited in non-soluble protein aggregates [3, 4]. Hemosiderin deposition in systemic iron overload classically follows a reticuloendothelial pattern that involves the liver, spleen, and bone marrow [2, 4, 5]. Iron deposition can alternatively involve the liver and pancreas in a parenchymal pattern, the kidneys in a renal pattern, or any combination of the aforementioned organs in a mixed pattern [5]. On the other hand, splenic iron deposition in the setting of a mass can occur when macrophages produce hemosiderin or due to localized heme breakdown, such as a chronic hematoma [5–7]. Magnetic resonance im
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