Temporoparietal dermoid cysts with intracranial extension.

A 9-month-old boy presented with a swelling in his left temporal area first noted by his mother 2 weeks prior to admission. Initially, the mass was soft and tender and the overlying skin was erythematous. Subsequently it enlarged and became firm and nontender. On physical examination, a firm, nontender 3 x 1 cm mass was palpated in the left temporal area, and a small black spot was noted on the overlying skin. Films of the skull (Fig. 1A) showed a vertical 3 x 0.4 mm groove with slightly sclerotic margins in the left temporal area, involving primarily the greater wing of the sphenoid. A CT scan of the skull (Fig. 1 B) showed a left temporal mass and a vertical groove with raised margins in the inner table of the skull, corresponding to the defect seen in the skull films. At surgery, white, cheesy material was found extruding from a small defect in the temporal bone. Adjacent to this area, beneath the temporal muscle, was some purulent material and a sinus tract leading to the skin anterior and above the left ear. The soft-tissue cyst, overlying skin , and a bone flap centering on the lesion were removed together with an intracranial, decompressed part of the cyst that showed no attachment to the dura. Histologic examination of the surgical specimen (Fig. 1 C) showed a ruptured dermoid cyst with a few eccrine glands and hair follicles beneath the epithelium lining. The cyst was surrounded by granulation tissue, and the section of the bone showed periosteal reaction with new bone formation , granulation tissue , and marked acute inflammation. Foreign-body giant cells were evidence of reaction to previous rupture.