Giant Cell Lesions of the Maxillofacial Skeleton Express RANKL by RNA In Situ Hybridization Regardless of Histologic Pattern.

Maxillofacial central giant cell lesions (CGCLs) are often locally aggressive tumors in young patients that may be histologically very similar to or quite distinct when compared with giant cell tumors (GCTs) of long bones. It has been well established that GCTs express high levels of receptor activator of nuclear factor-kappa B ligand (RANKL) and are amenable to treatment with denosumab. To assess the predictive value of morphology, we evaluated CGCLs with GCT-like or non-GCT-like histology for RANKL expression by RNA in situ hybridization. Tumors were classified by clinical and radiographic criteria as aggressive or nonaggressive and histopathologically as resembling GCT or non-GCT-like. RNA in situ hybridization for RANKL mRNA was performed and scored semiquantitatively based on the magnification at which the signal was first detected. There were 17 patients (M:F=8:9) with a median age of 15 years. Nine patients were children under 18 years of age. In 10 patients, tumors were characterized as GCT-like and in 7, non-GCT-like; 6 occurred in the setting of a known associated syndrome. Of the sporadic tumors, 9/11 (82%) were classified as aggressive. Fifteen of 17 (88%) tumors strongly expressed RANKL (8/9 aggressive, 2/2 nonaggressive; 10/10 GCT-like and 5/7 non-GCT-like). Two patients with clinically aggressive CGCL, GCT-like histology and high tumor RANKL expression were identified as candidates for a trial of denosumab with notable clinical response. CGCLs demonstrate strong and diffuse RANKL mRNA expression in mononuclear stromal cells, regardless of histology or presence of an associated syndrome. Denosumab may be clinically beneficial in aggressive CGCLs.