Glial heterotopia in the subcutaneous tissue overlying T-12

Heterotopic glial nodules occur most commonly in the head and neck area, and are theorized to arise following abnormalities in the development of the facial and skull bone plates. However, in spite of the fact that some of these lesions are associated with communication with the central nervous system (CNS), the lack of a meningeal component, argues against simple herniation and separation of brain tissue through a defect in the skull. We present an infant with a nodule directly over the spine present in the T-12 region with no skin abnormalities. Magnetic resonance imaging (MRI) and computerized axial tomography (CT) showed no spinal abnormalities with an overlying fibrotic soft tissue mass. The patient had no other associated clinical findings. Histologic findings showed a cellular component arising within the reticular dermis with a deep circumscribed margin. The nodule contained irregularly shaped cells containing abundant cytoplasm and indistinct cellular margins with bland nuclei. These cells were clustered around and between a fibro-mucinous stroma. Immunohistochemical stains showed positive staining for S-100 protein, vimentin, GFAP, NSE, and CD57, and negative staining for Ki-67, CD34, Neurofilament protein, cytokeratin, and EMA. The spindle cells showed positive staining for CD34 and vimentin. The clinical and histologic features and immunohistochemical profiles are used to separate this lesion from the closely related, ependymal rests, ependymomas, and primary cutaneous chorodomas.