A 12-year-old boy of McCune-Albright syndrome with an incidentally detected skull tumor

Abstract

McCune-Albright syndrome (MAS) is a disorder characterized by the triad of fibrous dysplasia (FD), café-au-lait spots (CAS), and endocrine abnormalities. Somatic mutations in the GNAS (guanine nucleotide binding protein, alpha stimulating) gene have been implicated in the etiology of MAS. We report the case of a 12-year-old male adolescent who was diagnosed with MAS following evaluation of an incidentally detected mass at the convexity of the skull. Computed tomography of the head performed at the time of a head injury revealed hypodensity in the right parietal bone, and the patient was referred to our hospital for further evaluation. Physical examination revealed that in addition to a bulge in the right parietal bone, the patient had CAS on the right shoulder. The lesions did not cross the midline and showed irregular margins. Gadolinium-enhanced T1- and T2-weighted magnetic resonance imaging of the head revealed a homogeneously enhanced mass with signal intensity equal to that of the cerebral cortex, and bone scintigraphy revealed tracer accumulation in the same region. In view of the possibility of neoplastic lesions, such as Langerhans cell histiocytosis, we removed the skull tumor 3 months after the head trauma. Based on histopathological evaluation of the resected tumor, and FD and CAS over the right shoulder, we clinically diagnosed the patient with MAS. Subsequent genetic analysis of the bone tumor tissue revealed a GNAS gene mutation, and the diagnosis of MAS was genetically confirmed. Cells with GNAS mutations can be distributed in a mosaic pattern throughout the body, including the bones, skin, and endocrine tissues. The detection rate of mutations in the peripheral blood is low, and genetic analysis of tissue samples obtained from lesions is useful for diagnostic confirmation of MAS. Diagnosis of FD based exclusively on imaging is challenging and may be inaccurate; therefore, biopsy-based pathologic and genetic analyses should be considered to confirm the diagnosis of MAS.