Case Presentation: A 40 year old woman with a history of pericarditis, initially thought to be due to a diagnosis of rheumatoid arthritis, presents with months of worsening fatigue, pleuritic chest pain, intermittent hemoptysis, and anemia. Had CT scans and subsequent PET scan showing multifocal FGD avid hypermetabolic lesions in the bilateral lungs, hypermetabolic soft tissue nodules abutting the spleen and superior stomach, a lytic lesion in the posterior right temporal bone, and patchy involvement of the right ascending colon. Initial CT-guided lung biopsy and pleural fluid studies were nondiagnostic, showing only inflammation. Infectious work-up was negative, including testing for HIV, TB, opportunistic infections. Systemic inflammatory markers including CRP and ESR were elevated. Although patient had positive ANA 1:160 with speckled pattern, other autoimmune markers were negative, and clinical presentation was not thought to be consistent with Rheumatoid Arthritis. She subsequently underwent a VATS biopsy of the largest lung mass, which confirmed a diagnosis of Inflammatory Pseudotumor on histopathologic review with proliferation of myofibroblast cells on a background of lymphoplasmacytic inflammation. Biopsy was negative for carcinoma or lymphoproliferative disorder. EBV and HHV8 negative. The ratio of IgG4/IgG ratio was less than 40%. No fusions were identified on a sarcoma targeted gene fusion panel, and there was negative ALK gene rearrangement on FISH. Given the diffuse nature of the lesions, they would not be amenable to surgical resection, she was instead started on prolonged steroid taper.
Discussion: Inflammatory pseudotumors are rare benign tumors commonly found in the lungs but can present in any organ1. They are commonly found as a singular mass or multiple masses. They are reactive in nature, with their etiology thought to be related to trauma, infection with pathogens such as EBV, HHV-8, or autoimmune with conditions such as IgG4-related disease or Sjögren’s syndrome2. The diagnosis of this condition is quite challenging as its clinical and radiographic findings can mimic that of malignant neoplasms. Diagnosis is often achieved with histopathologic testing. Histologically, there is lymphoplasmacytic infiltrate with varying populations of fibroblasts, myofibroblasts, lymphocytes, plasma cells, eosinophils, and histiocytes3. The tumor is also negative for ALK gene rearrangements, differentiating it from a more neoplastic process like inflammatory myofibroblastic tumor4. Surgical excision is often the gold standard with little recurrence in tumors limited to a single organ. Some studies have shown successful treatment with high dose steroids5.
Conclusions: This case highlights the challenges in diagnoses and treatment of inflammatory pseudotumors as they can be easily confused for malignant neoplasms based on clinical and radiographic findings.