Inflammatory pseudotumour of lymph node and spleen

Epidemiology

Inflammatory pseudotumour is thought to be a self-limiting reactive condition. Viruses, particularly EBV² and human herpes virus-8, have been implicated in the pathogenesis.

Clinical features

Inflammatory pseudotumour occurs across a wide age range. It is a rare cause of lymphadenopathy. Clinical features include weight loss, fever, fatigue, raised ESR and anaemia.

Histopathology

There is an admixture of bland spindle cells, myofibroblastic and/or histiocytic with a polymorphic inflammatory cell infiltrate, including lymphocytes, plasma cells and occasional granulocytes.

Immunohistochemistry

ALK-1	0/131, 0/102, 0/43
HHV8	0/131
CD68	6/81
SMA	5/61
Desmin	negative1
S-100	negative1
CD2	lymphocytes positive1
CD3	lymphocytes positive1
CD5	lymphocytes positive1
CD19	only lymphocytes in residual follicles positive1
CD20	only lymphocytes in residual follicles positive1
CD21	negative1
CD30	some immunoblasts positive1
CD35	negative1
CD43	lymphocytes positive1
CD45RO	lymphocytes positive1
light chain	polytypic1
Pan-cytokeratin, MNF-116	negative1
HMB-45	negative1

Differential diagnosis

• Inflammatory myofibroblastic tumour, which arises in soft tissues in children. The histology is very similar, but, particularly in the abdomen, the clinical course may be more aggressive with recurrences are, rarely, metastases. Chromosomal gene rearrangements suggest inflammatory myofibroblastic tumour is a true neoplasm. The cytogenetic abnormalities commonly involve the ALK gene at 2p23 and one of two tropomyosin genes, with resulting high levels of expression of ALK protein kinase, demonstrable by immunohistochemistry. An identical gene fusion product is seen in anaplastic large cell lymphoma.

• Inflammatory follicular dendritic cell tumour. EBV has also been implicated in the pathogenesis of this lesion.

References

¹Kutok, J. L., Pinkus, G. S., Dorfman, D. M., Fletcher, C. D. Inflammatory pseudotumor of lymph node and spleen: an entity biologically distinct from inflammatory myofibroblastic tumor. Human Pathol 2001;32:1382-1387.

²Neuhauser, T. S., Derringer, G. A., Thompson, L. D., Fanburg-Smith, J. C., Aguilera, N. S., Andriko, J., Chu, W., Abbondanzo, S. L. Splenic inflammatory myofibroblastic tumor (inflammatory pseudotumor): a clinicopathologic and immunophenotypic study of 12 cases. Arch Pathol Lab Med 2001;125:379-385.

³Cook, 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.

This page last revised 7.5.2002.

©SMUHT/PW Bishop