RESIDENT CASE STUDIES

Week 8 June 9 - June 13, 2003: Case 2   

Table of Contents | List of Diagnoses | Case 1 | Case 2 | Case 3

30 year old female with a 1.5cm nodular mass in the right lower lobe of lung

Discussion
Inflammatory pseudotumor (IPT), also known as inflammatory myofibroblastic tumor (IMT) and plasma cell granuloma, is a neoplastic, mostly benign lesion that commonly involves the lung and the orbit, but it has been reported to occur in nearly every site in the body.² Inflammatory pseudotumors are characterized by fibrotic ground tissue and polyclonal mononuclear infiltrate consisting of chronic inflammatory cells that are predominantly plasma cells.^3,4 Vancauwenbergh et al reported that IMT is the most frequent primary lung tumor in children under the age of sixteen⁵ and suggested that it should be part of the differential diagnosis of a solitary lung nodules in children. The clinical history and radiological diagnosis are often non-specific.⁵ 

Histologically, it is important to note that fibroblasts, myofibroblasts and inflammatory cells (mostly plasma cells, but also eosinophils and others inflammatory cells) may be present in varying proportion. Plasma cell infiltrate in IPT is polyclonal. A combination of atypia, ganglion-like cells, TP53 expression and aneuploidy may help identify IPT with a more aggressive potential.⁶

Recent genetic and molecular studies have shown that a subset of IPT is characterized by the expression of altered anaplastic lymphoma kinase (ALK), and such ALK-positive cells in IMT are not always myofibroblastic but might be immature primitive mesenchymal cells.¹

References:

¹Hisaoka M, Shimajiri S, Matsuki Y, et al. Inflammatory myofibroblastic tumor with predominant anaplastic lymphoma kinase-positive cells lacking a myofibroblastic phenotype. Pathol Int. 2003 Jun;53(6):376-381.

²Narla LD, Newman B, Spottswood SS, et al. Inflammatory pseudotumor. Radiographics. 2003 May-Jun;23(3):719-29.

3Misao T, Satoh K, Nakano H, Yamamoto Y. Pulmonary inflammatory pseudotumor with rapid growth and serum carcinoembryonic antigen elevation. Jpn J Thorac Cardiovasc Surg. 2003 Mar;51(3):104-6.

⁴Hausler M, Schaade L, Ramaekers VT, et al. Inflammatory pseudotumors of the central nervous system: report of 3 cases and a literature review. Hum Pathol. 2003 Mar;34(3):253-62.

⁶Hussong, JW, Brown, M, Perkins, SL, et al. Comparison of DNA ploidy, histologic and immunohistochemical findings with clinical outcome in inflammatory myofibroblastic tumors. Mod Pathol 1999;12:279-286.