Inflammatory pseudotumor (IPT) is a tumor-like mass pathologically composed of lymphocytes, plasma cells, histiocytes, macrophages, and foam cells within a spindle-shaped stroma.1, 2 Hepatitis C virus, EBV, HIV, bacterial, fungal, and mycobacterial infections have been known to precede the development of a pseudotumor.1, 2, 3 Associations with malignancy, trauma, surgery, and radiotherapy have also been reported.1 Although it is usually considered nonmalignant, it may occasionally have malignant potential.1 Three cases of IPT following HSCT have been reported.4, 5
A 50-year-old woman with AML in second remission underwent allogeneic blood HSCT after conditioning with 120 mg/kg cyclophosphamide and 12 Gy TBI. The patient was hospitalized for nephrotic syndrome secondary to chronic GVHD 15 months later, and treated with 0.5–1 mg/kg of prednisolone for a month with little effect. This was followed by 1000 mg methylprednisolone daily for 3 days with minor response. Cyclosporine was added a month later with improvement. Both agents were gradually reduced over the next 3–4 months.
Sensory disturbance involving the left side of the body developed during the taper. An MRI scan done a month later showed an intracerebral tumor with edema at the right frontal lobe and the right thalamus (Figure 1). Blood counts, LDH, and C-reactive protein were normal. IgG and IgA were low (368 and 50 mg/dl, respectively). With the possibility of a chloroma in mind, the marrow was evaluated and was found to be normal.
Owing to rapid clinical deterioration, tumor resection was performed 2 days after diagnosis followed by whole-brain radiation therapy before a histological diagnosis was available. She received 3 Gy once a day for 10 days. Histologically, the tumor showed lymphocytes, plasma cells, and histiocytes within a spindle-shaped stroma (Figure 2), consistent with IPT. No infection was observed in the cytological examination of the resected tumor. Despite measures to reduce the intracerebral pressure (betamethasone and glycerin), the consciousness level gradually deteriorated. A presumptive diagnosis of a fungal infection was made based upon fever and elevated beta-D-glucan. Despite anti-fungal therapy, the patient died of fungal infection approximately 5 months after diagnosis of IPT.
The course of this patient prior to the diagnosis of IPT was not atypical of such patients, and therefore it is difficult to attribute the occurrence of the IPT to specific factors such as chemotherapy, TBI, infection, or immunosuppression. The usual treatment for brain IPT is surgical resection combined with corticosteroids and/or radiation therapy. However, approximately 40% of patients experience intra- or extracranial recurrence within 2 years of primary surgery.6 Other treatment approaches such as chemotherapy or immunosuppressive therapy using cyclosporine may help reduce recurrence.2, 7, 8
Our experience and the literature suggests that IPT is a rare but potentially serious complication of HSCT, the optimum therapy of which remains undefined.
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Tsutsumi, Y., Kanamori, H., Kawamura, T. et al. Inflammatory pseudotumor of the brain following hematopoietic stem cell transplantation. Bone Marrow Transplant 35, 1123–1124 (2005). https://doi.org/10.1038/sj.bmt.1704955
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