Aims: To report a series of four paediatric cases of interdigitating dendritic cell sarcoma (IDCS) and add to the known extranodal sites of occurrence for this tumour. Neoplasms derived from interdigitating dendritic cells are rare, with only 33 cases being reported in the literature (Medline search). These tumours usually occur in lymph nodes in the adult population.
Methods and results: The patients were a 10-year-old girl with a large soft tissue mass bulging into the left chest, a 12-year-old girl with a right paraspinal mass, a 21-month-old boy with generalized lymphadenopathy and hepatosplenomegaly and a 6-year-old girl with a large bladder mass. Paraffin blocks and haematoxylin and eosin slides were available in all cases. In addition, immunohistochemistry and electron microscopy were performed. A diagnosis of IDCS was made in all cases.
Conclusion: The diagnosis of IDCS can rarely be entertained on clinical information alone. Microscopically, there is a wide spectrum of features. Thus, immunohistochemistry and electron microscopy are crucial in making the diagnosis. The differential diagnosis includes inflammatory pseudotumour, follicular dendritic cell sarcoma, true histiocytic lymphoma, malignant Langerhans cell histiocytosis, anaplastic large-cell lymphoma, melanoma, and a range of sarcomas. IDCS displays aggressive behaviour and approximately half of the patients die of the disease.