This study aimed to determine the features and differentiation of Giant Cell Reparative Granuloma (GCRG) and Giant Cell Tumor (GCT) of the head on CT and MRI.
This retrospective study included six patients with histopathology-confirmed head GCRG and 5 patients with histopathology-confirmed head GCT. All images were independently reviewed by two radiologists. The growth pattern, bone changes, MRI signal intensity, enhancement patterns and other image features were recorded. All patients received CT scans and MR images.
All the lesions were located centrally in the bone. Osteolytic bone destruction and expansive growth patterns were observed on CT images. Four of six cases broke the cortical bone with residual cortical bone, and the last two showed a thin cortex in GCRG. Five cases broke the cortical bone with residual cortical bone in GCT. There were enhancing septations in GCT lesions on contrast- enhanced T1-Weighted Images (T1WI) while enhancing septations were not present in GCRG cases. The size of GCT lesions was larger than that of GRCG. GCRG and GCT showed iso-low signals on T1WI and iso-high signals on T2-Weighted Images (T2WI). There was a case with cystic or necrotic lesions in each of the two types of lesions. Osteolytic bone destruction and expansive growth patterns were observed in GCTs and GCRGs.
The size of the GRCG lesion was smaller than that of the GCT. The presence of enhancing septations and the size of the lesion may distinguish GCTs from GCRG.

Giant cell reparative granuloma (GCRG) is a non-neoplastic hyperplasia of bones that mostly happens in the mandible and maxilla in any age group but has a predilection for children and young adults. GCRGs that cause bone destruction are of very low frequency. Orbital-involved cases have been rarely reported since 1981, especially in children. We now report a 1-year-old girl with a rapidly enlarging post-traumatic orbital mass. CT scan and surgical resection showed a well-defined mass occupying the upper right orbit, causing bone destruction. Microscopically there was a proliferation of histocytes and some osteoclast-like multinucleated giant cells with hemosiderin, finally confirmed to be GCRG. 22 months\' follow up showed no evidence of recurrence. This case suggests infant orbital GCRG can be locally aggressive.

BACKGROUND: Giant cell reparative granuloma (GCRG) is a rare benign tumor. The jawbone is the most common site of occurrence, followed by sphenoid bone, craniofacial bone, hand and foot bones. The etiology of GCRG is unknown but may be related to an intraosseous hemorrhage following trauma. Despite its benign nature, it could be locally aggressive. To our knowledge, no spinal epidural GCRG case has been reported.
METHODS: A case of man aged 32 years who presented with upper right limb numbness and weakness. Computed tomography showed a round soft tissue mass in the spinal canal at the C7-T1 level. The mass showed isointensity on T1-weighted images, hypointensity on T2-weighted images, and significant enhancement on postcontrast T1-weighted images. The mass localized in the epidural space and was surgically resected. The histologic diagnosis was consistent with GCRG.
CONCLUSIONS: Spinal epidural GCRG is rare and is hardly considered in the differential diagnosis. Preoperative diagnosis of GCRG is challenging, and the definitive diagnosis could only be made by pathological examination. Surgical resection is probably an effective therapy for relief of symptoms.