Interdigitating dendritic cell sarcoma/tumour of the tonsil

Abstract

A 55-year-old Caucasian male presented with a painless enlargement of the right tonsil, which he had noticed 6 months previously. No general symptoms were reported and he denied any significant past medical history. No lymphadenopathy, hepatomegaly or splenomegaly was present. Laboratory examination was normal. A bilateral tonsillectomy was performed. Microscopic examination demonstrated effacement of the normal architecture of the right palatine tonsil by diffuse proliferation of large and irregularly shaped histiocytoid cells (top left). In some areas the tumour cells were spindle shaped and surrounded by a fine, collagenous stroma (top right). Polylobated and multinucleated forms were also present (bottom left). The neoplasm was not encapsulated and extended up to the epithelium. On immunohistochemical examination the tumour cells were moderately to strongly immunoreactive for vimentin and S-100 protein (bottom right) and focally reactive for CD68 (KP-1), CD1a and lysozyme. Other immunostains, including cytokeratin, actin, desmin, HMB-45, B-cell and T-cell markers, CD30 and follicular dendritic cell (FDC) markers including CD21 and CD35, were negative. Based on morphological features and immunohistochemistry a diagnosis of interdigitating dendritic cell sarcoma/tumour was suggested. The patient received local radiation treatment and was free of disease at 6 months follow-up. Since 1982, there have been just 37 reported interdigitating dendritic cell tumours, with only one case arising in the tonsil (Gaertner et al, 2001). In the present case, the tumour appeared as a localized mass in an otherwise asymptomatic patient.