Inflammatory myofibroblastic tumour of the lung


An inflammatory "pseudotumour" composed of collagen, inflammatory cells and bland spindle cell of myofibroblastic differentiation.


Inflammatory pseudotumour, plasma cell granuloma, plasma cell/histiocytoma complex, fibroxanthoma, xanthogranuloma, fibrous histiocytoma, organising pneumonia, invasive fibrous tumour of the tracheobronchial tree.

Similar lesions occur in the mediastinum, intestinal mesentery, bone and urinary bladder.


Occurring at any age, inflammatory myofibroblastic tumour is most common before the age of 40 years.


There is increasing evidence that these tumours should be subdivided into those that are non-neoplastic inflammatory lesions (inflammatory pseudotumour) and those that are true neoplasms, showing cytogenetic abnormalities and gene mutation, with the associated potential for more aggressive behavior3, designated as inflammatory myofibroblastic tumour. The true neoplasms may be aneuploid and show p53 mutations. Cytogenetic abnormalities have been shown on chromosome 2 at 2p2310, in proximity to the ALK gene, with formation of fusion products incorporating the ALK gene and immunohistochemical expression of ALK. ALK positivity is less common in pseudotumour of the lung than at other sites2.

A second subset of inflammatory pseudotumours appear to be reactive and associated with various infective agents, including Epstein-Barr virus, Actinomyces, Pseudomonas species, mycoplasma and human herpes virus-82,8. The principle cell in this type appears to be the follicular dendritic cell.

Clinical features

80% of patients are symptomatic5, with endobronchial lesions resulting in cough, wheeze or haemoptysis4. Constitutionally, there may be weight loss, fever or fatigue5. Invasion of the chest wall by peripheral lesions results in pleuritic or chest wall pain.


There is a solitary mass which may have spiculated margins. If endobronchial, there may be postobstructive pneumonia or atelectasis. The lesion may be radiologically indistinguishable from pulmonary sequestration11.

Macroscopic appearance

The tumour forms a rubbery mass which is not encapsulated. There may be calcification. Cavitation is not common.


Matsubara proposed three forms, with overlap9:


smooth muscle actin

9/91, 4/46


9/91, 4/46


0/91, 0/46


focally positive in one third of cases0, 0/91, 0/46


positive in 40% of cases0, 3/91








negative0, 0/46


The extrapulmonary cases more often show positivity for cytokeratins.

Differential diagnosis


Complete resection4. If incompletely resected, the residual tumour will continue to grow5.


Complete excision is commonly curative5. Recurrences7 and metastases are rare. Local invasion, vascular invasion, increased cellularity and pleomorphism, a high mitotic rate (greater than 3 per 50 HPF) and necrosis are associated with poor prognosis7.


0 Tumours of the Lung, Pleura, Thymus and Heart. WHO Classification of Tumours. IARC Press 2004.

1 Yousem, S. A., Shaw, H., Cieply, K. Involvement of 2p23 in pulmonary inflammatory pseudotumors. Human Pathol 2001;32:428-433.

2 Cook, J. R., Dehner, L. P., Collins, M. H., Ma, Z., Morris, S. W., Coffin, C. M., Hill, D. A. Anaplastic lymphoma kinase (ALK) expression in the inflammatory myofibroblastic tumor: a comparative immunohistochemical study. Am J Surg Pathol 2001;25:1364-1371.

3 Coffin, C. M., Patel, A., Perkins, S., Elenitoba-Johnson, K. S., Perlman, E., Griffin, C. A. ALK1 and p80 expression and chromosomal rearrangements involving 2p23 in inflammatory myofibroblastic tumor. Mod Pathol 2001;14:569-76.

4 Alexiou C, Obuszko Z, Beggs D, et al. Inflammatory pseudotumors of the lung. Ann Thorac Surg 1998; 66:948-50

5 Cerfolio RJ, Allen MS, Nascimento AG, et al. Inflammatory pseudotumors of the lung. Ann Thorac Surg 1999; 67:933-6

6 Barbareschi M, Ferrero S, Aldovini D, et al. Inflammatory pseudotumour of the lung. Immunohistochemical analysis on four new cases. Histol Histopathol 1990; 5:205-11

7 Gal AA, Koss MN, McCarthy WF, et al. Prognostic factors in pulmonary fibrohistiocytic lesions. Cancer 1994; 73:1817-24

8 Gomez-Roman JJ, Sanchez-Velasco P, Ocejo-Vinyals G, et al. Human herpesvirus-8 genes are expressed in pulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor). Am J Surg Pathol 2001; 25:624-9

9 Matsubara O, Tan-Liu NS, Kenney RM, et al. Inflammatory pseudotumors of the lung: progression from organizing pneumonia to fibrous histiocytoma or to plasma cell granuloma in 32 cases. Hum Pathol 1988; 19:807-14

10 Snyder CS, Dell'Aquila M, Haghighi P, et al. Clonal changes in inflammatory pseudotumor of the lung: a case report. Cancer 1995; 76:1545-9

11 Souid AK, Ziemba MC, Dubansky AS, et al. Inflammatory myofibroblastic tumor in children. Cancer 1993; 72:2042-8


This page last revised 14.5.2005.