GIANT CELL REPARATIVE GRANULOMA OF ZYGOMA

Giant cell reparative granuloma of the skull bones is rare. It resembles giant cell tumours, aneurysmal bone cyst, hyperparathyroidism, posing difficulty in diagnosis. We report here our experience of giant cell reparative granuloma affecting zygoma mimicking giant cell tumour. Diagnosis was confirmed only by histopathology.

INTRODUCTION

Giant cell reparative granuloma of the skull bones is rare. Our experience of one patient with this unusual tumour prompted this case report.

CASE REPORT

A 55 year old man presented with slowly growing swelling on the left side of the face, in front of the ear of six months duration. It was associated with mild pain. He also had decreased hearing since four months. There was no history of headache, vertigo, nasal complaints or weakness of facial muscles. On examination, he had a firm, minimally tender, immobile swelling on the left side of face in front of the ear. There was no lifting off of pinna. The skin was free from swelling. On compression of the swelling, he had twitching of facial muscles. FNAC suggested giant cell tumour of soft tissue origin. The differential diagnosis included giant cell reparative granuloma, giant cell tumour, aneurysmal bone cyst, hyperparathyroidism. Hyperparathyroidism was ruled out by biochemical investigations. Local X-rays did not reveal any bony involvement. At surgery, a cystic swelling of 9 x 7 cms in left preauricular region involving upper branches of facial nerve was found. The swelling was infiltrating into the mastoid and zygomatic bones suggesting origin from either of these bones. The tumour was excised from all around. The upper divisions of facial nerve were dissected and preserved. The other branches of facial nerve were not disturbed. The defect in mastoid was covered with temporalis muscle rotation flap. There was no facial paralysis postoperatively. Postoperative CT scan done later, suggested tumour arising from zygomatic bone and spreading upto the mastoid, para-pharyngeal space (Fig. 1).

Histopathology revealed connective tissue stroma composed of proliferating fibroblasts with small capillaries. Osteoclast like cells were seen amidst the stroma with haemosiderin laden macrophages and areas of haemorrhage and foci of osteoid, diagnosing giant cell reparative granuloma (Fig. 2).


Fig. 1: Postoperative CT scan showing tumor arising from left zygomatic bone and reaching upto left mastoid, parapharyngeal space.	Fig. 2: Microphotograph showing connective tissue stroma composed of proliferating fibroblasts with small capillaries. Osteoclast like cells are seen amidst the stroma with haemosiderin laden macrophages and areas of haemorrhage and foci of osteoid, diagnosing giant cell reparative granuloma. (H and E x 160).

DISCUSSION

Giant cell reparative granuloma (GCRG) is an uncommon benign lesion of the bone. It typically arises in the mandible and rarely involves the skull. GCRG is common in younger age group, but 20% of patients were old over 50 years of age in one series.[1] Histologically, the lesion is composed of small, elongated or oval shaped mononuclear stromal cells and multinucleated giant cells.[2] Although, it is believed to be non-neoplastic the lesion grows quite rapidly.[2] This often may be misdiagnosed as giant cell tumour.[3] Clinical distinction between the two lesions is of great prognostic importance. [3]

GCRG is thought to be the outcome of haemorrhagic phenomenon forming part of an inflammatory and/or infective process involving an area of bone. Pregnancy seems to favour the growth of the lesion.[4]

GCRG in the temporal bone is reported in only one case till 1974.[3] A three year old case of recurrent GCRG of petrous bone is reported.[2] Another case of GCRG of cricoid cartilage is reported.[1]

CT scan is excellent for evaluation of destructive lesions of the temporal bone and provides additional information concerning tissue characteristics of the mass, the presence of calcifications and tumour extension.[5] FNAC and CT scan can almost distinguish between the lesions preoperatively.

Treatment consists of curettage of the affected area. If this is not possible, partial removal combined with a low total dose of high voltage radiotherapy.

This may be sufficient for a cure. While surgery or surgery plus radiotherapy often affords permanent cure for GCRG only 12-16% recurrence in the larger series, a giant cell tumour cells for a more aggressive treatment, failing which there is a risk of recurrence or malignant transformation.[4]

In our patient complete excision with curettage was done. Histopathological diagnosis was giant cell reparative granuloma. He was doing well at two months follow-up.

REFERENCES

1.Thomas DM, Wilkins MJ, Witana JS, Cook T, Jeffezis AF, Walsh-Waring GP. Giant cell reparative granuloma of the cricoid cartilage. J Laryngol and Otol 1995; 105 : 1120-3.

2.Maruno M, Yoshimine T, Kubo T, Hayakaw T. A case of giant cell reparative granuloma of the petrous bone. Demonstration of the proliferative component. Surg Neurol 1997; 48 : 64-8.

3.Katz A, Hirschi S. Giant cell reparative granuloma in the temporal bone. Arch Otolaryngol 1974; 100 : 380-2.