Desmoplastic Fibroma of the Cranium in a Young Man
A 20-year-old man visited our clinic with a 1-year history of worsening headache and swelling of the right frontal region. Physical examination revealed bony swelling with a smooth cortical lining. The swollen area was mildly tender, and the overlying scalp was intact. Neurological examination was unremarkable. Plain skull X-ray films demonstrated a lytic lesion with a sclerotic margin. A computed tomographic (CT) scan demonstrated a 3×3.5-cm focal calvarial thickening and expansion of the diploic space by a hypo-attenuated mass with a sclerotic margin and ground-glass appearance. Magnetic resonance imaging showed heterogeneous signal intensity on T2-weighted images and intermediate signal intensity on T1-weighted images with multifocal enhancement (). There was no soft tissue or intracranial invasion. Focal hot uptake at the lesion site was observed on bone scan.\nThe patient underwent a craniectomy under general anesthesia. The lesion was completely excised with sufficient safety margins by inspection under guidance of intra-operative navigation. There were neither scalp nor dural invasions. The gross specimen was bulging with a pinkish color at the lesion site, which contained a round dark-brownish area with a sclerotic margin in the diploic space, slightly expanded and thicker compared to normal bone flaps. Sectioning after decalcification revealed an ill-defined fibrotic area. The lesion was accompanied by yellow necrotic foci and exhibited fibroblastic proliferation within a collagenous background, with extensive hemorrhage and fat necrosis. Tumor cells included spindle cells and lacked significant unclear atypia and mitotic figures. These findings suggested desmoplastic fibroma of the skull. Immunohistochemical stain for smooth muscle actin (SMA) was focally positive (), and S-100 was positive. Other markers such as EMA, CD34, CD68, vimentin, and desmin were negative. All margins were free of tumor cells.