Inflammatory pseudotumor

Pathophysiology

The etiology and pathophysiology of hepatic inflammatory pseudotumors are unknown; however, they are thought to involve an inflammatory process. Inflammatory pseudotumors of the liver are benign tumorlike lesions that often appear to arise from a healing abscess or other inflammatory condition with rupture of the bile ducts and extravasation of bile into the tissue, which induces an inflammatory response with scarring. Some reported etiologies include past infection, trauma, vascular causes, and autoimmune disorders.

Epidemiology

A vast majority of inflammatory pseudotumors occur in childhood and early adulthood. However, they have been reported in patients of all ages. Male-to-female ratio ranges from 1-1 to 3.5-1. They appear to be more common in non-European populations. Incidence of hepatic inflammatory pseudotumors is close to 0.7%.

Clinical presentation

Patients usually present with abdominal pain, fever, malaise, or weight loss. Some patients are asymptomatic.

Imaging findings

On CT scans, they appear to be well-circumscribed or poorly marginated heterogenous lesions. Compared to a hepatocellular carcinoma, pseudotumors have nonspecific features on a delayed-phase CT scan.

Microscopic features

The histological appearance of these tumors is variable. Generally, there is a benign spindle cell proliferation in a background of inflammatory cells such as lymphocytes, plasma cells, and histiocytes. In most cases, there is a prominent proliferation of bile ducts (ductular reaction). Fibrosis in the background is also frequently encountered.

No laboratory or immunohistochemical markers are useful for diagnosing hepatic pseudotumors. The goal of doing immunostains in these cases is to exclude differential diagnoses, including IgG4 disease, Langerhans cell histiocytosis, hepatocellular carcinoma, and cholangiocarcinoma.

References

1. Balabaud C, Bioulac-Sage P, Goodman ZD, Makhlouf HR. Inflammatory pseudotumor of the liver: A rare but distinct tumor-like lesion. Gastroenterol Hepatol. 2012;8(9):633-634.
2. Zhao J, Olino K, Low LE, Qiu S, Stevenson HL. Hepatic inflammatory pseudotumor: An important differential diagnosis in patients with a history of previous biliary procedures. ACG Case Rep J. 2019;6(1):e00015. doi:10.14309/crj.0000000000000015.
3. Park JY, Choi MS, Lim YS, et al. Clinical features, image findings, and prognosis of inflammatory pseudotumor of the liver: A multicenter experience of 45 cases. Gut Liver. 2014;8(1):58-63. doi:10.5009/gnl.2014.8.1.58.
4. Yoon KH, Ha HK, Lee JS, et al. Inflammatory pseudotumor of the liver in patients with recurrent pyogenic cholangitis: CT-histopathologic correlation. Radiology. 1999;211(2):373-379. doi:10.1148/radiology.211.2.r99ma36373.
5. Jaïs P, Berger JF, Vissuzaine C, et al. Regression of inflammatory pseudotumor of the liver under conservative therapy. Dig Dis Sci. 1995;40(4):752-756. doi:10.1007/BF02064975.
6. Hakozaki Y, Katou M, Nakagawa K, Shirahama T, Matsumoto T. Improvement of inflammatory pseudotumor of the liver after nonsteroidal anti-inflammatory agent therapy. Am J Gastroenterol. 1993;88(7):1121-1122.