Enlarging Liver Mass: Inflammatory Pseudotumor in a Patient With Polymyalgia Rheumatica

Inflammatory pseudotumors of the liver are rare, non-neoplastic liver tumors. Due to the nonspecific clinical presentation, imaging features, and histopathological findings, they can mimic malignant tumors requiring invasive diagnostics. We present a case of a 61-year-old female patient with a history of type 2 diabetes mellitus, hypothyroidism, hyperlipidemia, and polymyalgia rheumatica who had initially presented with abdominal pain for 3 weeks. Further workup showed normal liver chemistries and tumor markers: AFP and CA 19-9. Magnetic resonance imaging (MRI) of the abdomen showed a segment 6 lesion measuring 4.1 x 4.0 x 3.7 cm. A liver biopsy then confirmed the diagnosis of an inflammatory pseudotumor of the liver with negative IgG4. On follow-up imaging, a rapid growth of this liver lesion was noted. Laparoscopy was done but did not show any distinct liver lesion. Follow-up imaging confirmed a decrease in the size of the mass. Interestingly, the patient had been on a higher dose of steroids for her polymyalgia rheumatic leading up to the follow-up imaging. This is the first case of an inflammatory pseudotumor of the liver in a patient with polymyalgia rheumatica. With this case, we would like to increase the awareness for inflammatory pseudotumors of the liver as a differential diagnosis of liver lesions in patients with underlying autoimmune disorders.