Unusual recurrent orbital tumour

Abstract

Abstract Purpose: We present a case of an unusual CD34+ recurrent orbital tumour. Methods: A 62‐year‐old male presented with progressive left proptosis and preserved visual acuity. CT scans showed a circumscribed mass at the inferomedial orbit. After incisional biopsy, the patient preferred conservative treatment and the lesion was debulked. Further debulking was necessary in other two occasions. With radiological signs of bone invasion, left orbital exenteration was agreed in the fourth relapse. Results: The lid skin sparing exenteration revealed a tumour mass (45 x 29 x 27 mm) in the inferomedial orbit. There was no evidence of invasion of either the globe or the optic nerve. In all occasions, the tumour consisted of spindle cells alternating vague storiform areas with patternless areas. The tumour was very cellular, showed low mitotic count and no necrosis or ulceration. There was focal invasion of fibrous tissue, extra‐ocular muscle, fat and bony fragments. The tumour was diffusely and consistently positive for CD34, S100 and vimentin. EMA and CD99 were focally positive. Several other markers were negative. This slow growing lesion with low grade histological appearance and EM suggestive of Schwannian processes was diagnosed as a CD34 positive Schwannoma on the first debulking. In the next two recurrences, experts agreed with a diagnosis of a DFSP based on the diffuse positivity for CD34. In the exenteration specimen, due to the exceptional location of the presumable DFSP, this diagnosis was disputed and after EM and further reviews the case was concluded as variant of low grade MPNST. Conclusions: The consistent positivity for CD34 in our case has lead to diagnostic disagreement. Only after the fourth recurrence the final diagnosis of a CD34 positive low grade PNST could be made.