The role of T2*-weighted gradient echo in the diagnosis of tumefactive intrahepatic extramedullary hematopoiesis in myelodysplastic syndrome and diffuse hepatic iron overload: a case report and review of the literature

Abstract

Background: Extramedullary hematopoiesis is the proliferation of hematopoietic cells outside bone marrow secondary to marrow hematopoiesis failure. Extramedullary hematopoiesis rarely presents as a mass-forming hepatic lesion; in this case, imaging-based differentiation from primary and metastatic hepatic neoplasms is difficult, often leading to biopsy for definitive diagnosis. We report a case of tumefactive hepatic extramedullary hematopoiesis in the setting of myelodysplastic syndrome with concurrent hepatic iron overload, and the role of T2*-weighted gradient-echo magnetic resonance imaging in differentiating extramedullary hematopoiesis from primary and metastatic hepatic lesions. To the best of our knowledge, T2*-weighted gradient-echo evaluation of extramedullary hematopoiesis in the setting of diffuse hepatic hemochromatosis has not been previously described.

Case presentation: A 52-year-old white man with myelodysplastic syndrome and marrow fibrosis was found to have a 4 cm hepatic lesion on ultrasound during workup for bone marrow transplantation. Magnetic resonance imaging revealed diffuse hepatic iron overload and non-visualization of the lesion on T2* gradient-echo sequence suggesting the presence of iron deposition within the lesion similar to that in background hepatic parenchyma. Subsequent ultrasound-guided biopsy of the lesion revealed extramedullary hematopoiesis. Six months later, while still being evaluated for bone marrow transplant, our patient was found to have poor pulmonary function tests. Follow-up computed tomography angiogram showed a mass within his right main pulmonary artery. Bronchoscopic biopsy of this mass once again revealed extramedullary hematopoiesis. He received radiation therapy to his chest. However, 2 weeks later, he developed mediastinal hematoma and died shortly afterward, secondary to respiratory arrest.

Conclusions: Mass-forming extramedullary hematopoiesis is rare; however, our report emphasizes that it needs to be considered in the initial differential diagnosis of hepatic lesions arising in the setting of bone marrow disorders. We also show that in the setting of diffuse hepatic iron overload, tumefactive extramedullary hematopoiesis appeared isointense to background liver on T2* gradient-echo sequence, while adenoma, hepatoma, and hepatic metastasis appear hyperintense. Thus, T2*-weighted gradient-echo sequence may have a potential role in the imaging diagnosis of mass-forming hepatic extramedullary hematopoiesis arising in the setting of diffuse iron overload.

Keywords: Hepatic extramedullary hematopoiesis; Iron; MRI; Myelodysplastic syndrome; T2*.

Fig. 1

a Liver sagittal ultrasound shows a hypoechoic lesion in the right hepatic lobe (white arrow). b Axial T1-weighted volumetric interpolated breath-hold examination pre-contrast image shows a lesion in segment 7 (white arrow) that is hypointense to hepatic parenchyma. c After 20 cc of intravenous MultiHance® contrast agent administration heterogeneous mild enhancement was detectable in the arterial phase (white arrow). d, e The lesion washes out to isointensity in the portal venous and 5-minute delayed phases. f Axial T2*-weighted gradient echo shows decreased liver and spleen signal intensity, lower than that of the paraspinal musculature, consistent with diffuse parenchymal iron deposition, with non-visualization of the segment 7 lesion due to iron deposition similar to the rest of the hepatic parenchyma (white arrow). g Diffusion-weighted axial scan shows absence of restriction and non-visualization of the lesion (white arrow). h Hematoxylin and eosin stain demonstrates a sinusoidal-based infiltrate of bone marrow elements, including three megakaryocytes at the lower right (black arrows). i C-KIT immunostain highlights frequent myeloid blasts (black arrow), reflecting this patient’s evolving myelodysplastic syndrome. j Perls’ iron stain highlights massive iron accumulation (black arrow). k Blood smear with Wright’s stain, × 500, oil emersion demonstrates a peripheral monocytosis (the larger cells with convoluted nuclei and pale, basophilic, vacuolated cytoplasm, thick arrows) and left-shifted granulopoiesis with a few bands and a single myeloid blast (thin arrow); a nucleated red blood cell is also noted in the right half of the image (dashed arrow). l, m Computed tomography angiogram of the chest shows an enhancing mass within the right main pulmonary artery suggestive of tumor thrombus (white arrow)