Abstract

Primary Giant Cell Tumour of Soft Tissue (GCT-ST), also known as soft tissue giant cell tumour of low malignant potential, is a rare soft tissue tumour. Histologically, these lesions bear a close resemblance to their bony counterparts, GCT of bone. Although predominantly a benign condition, its capacity to recur or evolve into malignant lesion is well recognized. The lesions are usually superficial and involve lower extremities and trunk but rarely occur in head and neck. Here we report a rare benign primary GCT-ST at an uncommon location. A 27-year-old Malay gentleman presented with painless right forehead swelling for three months. Physical examination revealed a mobile, benign looking superficial skin lesion measuring 3x1cm. Grossly, the lesion showed greyish solid surface enwrapped by thin pseudo-capsule. Microscopically, it composed of round to oval mononuclear cells intermixed with osteoclast-like giant cells. The mononuclear cells displayed mildly pleomorphic vesicular nuclei with small nucleoli and moderate amount of cytoplasm. Mitotic figures were frequent, but no atypical form was observed. The neoplastic cells were weak and diffusely expressing SMA. Homogenous and strong expression of CD68 was noted on the osteoclast-like giant cells. GCT-ST is an uncommon but distinct entity. It is important to recognise this pathological entity in order to avoid misdiagnosis with other fibrous tumour associated with giant cells such as GCT of tendon sheath, nodular fasciitis, benign fibrous histiocytoma and undifferentiated pleomorphic sarcoma. Complete excision with negative margins results in benign clinical course because distant metastasis and tumour-associated death seem to be exceedingly rare.

Keywords:Giant cell tumour; Soft tissue; Scalp; Uncommon location