Follicular dendritic cell tumour/sarcoma (FDCT) is a rare tumour that characteristically shows immunoreactivity for CD21, CD23 and CD35.1 To date there is no published literature on CD99 immunoreactivity in FDCT. We recently encountered two cases of FDCT, both of which expressed CD99.

The first patient (case 1) was a HIV-positive man in his 30s who had an extensive extradural spinal mass (fig 1A) which infiltrated the C4/C5 intervertebral disc causing pathological fracture of C5 with posterior subluxation (fig 1B, C). The patient had been diagnosed 2 years previously with FDCT in a cervical lymph node that was completely excised. Histological examination of the spinal lesion revealed a spindle cell tumour arranged in interlacing fascicles, with some areas of whorling, and scattered infiltrate of small lymphocytes. The spindle cells …