Myoepithelioma of the Skull

Abstract BACKGROUND AND IMPORTANCE: Myoepithelioma of bone is a rare osseous tumor thought to be related to myoepithelial lesions found at other anatomic sites such as the salivary gland and skin. These tumors are composed of varying proportions of epithelial and myoepithelial cells and exhibit a spectrum of biologic behavior ranging from benign to malignant. We present the first reported case of myoepithelioma of the skull. CLINICAL PRESENTATION: A 20-year-old white woman presented with a persistent right parieto-occipital skull nodule, relating its presence to a fall on the site 2 years previously. The nodule had become painful in the past 2 months. Her past medical history and workup were otherwise unremarkable. The initial biopsy was inconclusive for diagnosis. The lytic bone lesion was subsequently resected, and histopathological examination showed a proliferation of epithelioid cells in a myxochondroid background. Fluorescence in situ hybridization studies revealed a rearrangement of the EWSR1 locus. The morphologic and molecular findings were consistent with the diagnosis of myoepithelioma of bone. CONCLUSION: Six months after surgery, the patient is doing well with no evidence of recurrence. This case illustrates the clinical presentation, histopathology, and molecular findings of a myoepithelioma of the skull with successful surgical treatment. Because myoepitheliomas with benign morphological appearance may rarely act aggressively, long-term clinical follow-up is warranted.