F-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Appearance of Extramedullary Hematopoesis in a Case of Primary Myelofibrosis

A 44-year-old female presented with recurrent episodes of epistaxis. On subsequent evaluation, she was found to have leukoerythrobastic picture in peripheral blood with bicytopenia. On physical examination, massive splenomegaly was noted. A provisional diagnosis of primary myelofibrosis was made based on the above-mentioned findings. For further confirmation, bone marrow biopsy was performed which revealed a hypercellular marrow (60%), polymorphous trilineage hematopoiesis and moderate to severe reticulin fibrosis. So based on bone marrow biopsy, primary myelofibrosis was confirmed. The patient was initiated with lenalidomide and steroid. She was improved on the same with subsequent improvement in the platelet count and became transfusion independent. After 1 year of disease-free interval, she presented with shortness of breath. HRCT thorax revealed large heterogeneously enhancing extraparenchymal soft tissue density mass involving bilateral lung fields. For further evaluation of the lung mass fluorodeoxyglucose (FDG) positron emission tomography/computed tomography was performed which revealed minimally FDG avid soft tissue density mass with dense calcification involving liver and spleen [Figures 1A–C]. Along with that large heterogeneously enhancing extraparenchymal soft tissue density mass noted with specks of calcification along costal pleura projecting into bilateral lung parenchyma showing minimal FDG uptake in the periphery with non FDG avid areas in the centre possibly represents area of necrosis [Figures 1D–I]. Based on her initial diagnosis of primary myelofibrois and low FDG avidity of the lesions a provisional diagnosis of extramedullary hematopoesis (EMH) was made and histopathologic confirmation was suggested. Subsequent histopathologic evaluation from the right lung mass confirmed the diagnosis of EMH.

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Figure 1 (a-c) FDG PET-CT was performed which revealed minimally FDG avid soft tissue density mass with dense calcification involving liver and spleen [. (d-i) Along with that large heterogeneously enhancing extraparenchymal soft tissue density mass noted with specks of calcification along costal pleura projecting into bilateral lung parenchyma showing minimal FDG uptake in the periphery with non FDG avid areas in the centre possibly represents area of necrosis

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Primary myelofibrois is a BCR-ABL negative myeloproliferative neoplasm,[1] characterized by progressive bone marrow fibrosis and ineffective erythropoiesis.[2] EMH is a well-recognized phenomenon of this disease process.[3] The pathophysiology of EMH is thought to be associated with the constitutive mobilization of CD34+ cells into the peripheral blood. This dysregulation of hematopoietic stem cell trafficking likely ultimately leads to the seeding of extramedullary sites.[4] Liver and spleen are the most common sites of EMH, but it has been reported in skin, breast, gastrointestinal tract, lymph node, lung, thyroid gland, and conjunctiva.[56] To date, only few cases have reported FDG PET-CT appearance of EMH,[78] with EMH detected as a benign mass with low SUVmax values and normal appearance of the tissue, which is consistent with the findings of our case. The concurrent presence of an underlying hematopoietic disorder may further suggest a diagnosis of EMH. Thus in patients with hematologic disorder, EMH should be kept as a differential diagnosis in evaluation of any sift tissue mass and FDG PET-CT may be helpful in this case by distinguishing benign EMH which demonstrate low SUVmax from malignant lesions with high SUVmax values.