Thomas C. Cannon

Medullomyoblastoma: case report.

This 7-year-old boy presented with a 2-week history of headache, nausea, vomiting, anorexia, lethargy, and unsteadiness of gait. Brain magnetic resonance imaging (MRI) revealed a cystic mass within the vermis of the cerebellum. A suboccipital craniectomy was performed to remove a tumor that contained primitive neuroectodermal cells with florid skeletal muscle differentiation. Immunohistochemical studies and electron microscopy confirmed the presence of both a primitive neuroectodermal component and rhabdomyoblastic differentiation, consistent with the diagnosis of medullomyoblastoma. This exceedingly rare tumor of the cerebellar vermis of children is characterized by two components: primitive neuroectodermal tumor cells and skeletal muscle. Although the histogenesis remains uncertain, advances in immunohistochemistry and electron microscopy suggest the origin of this tumor from a multipotential stem cell precursor. (J Child Neurol 2001 ; 16 :598-599).

Survey of sinonasal inverted papillomata for Epstein-Barr virus

Several studies have indicated an etiologic role for viruses in the development of sinonasal inverted papillomata (IP). A recent report demonstrates a strong relationship (65%) between Epstein‐Barr virus (EBV) and these lesions using polymerase chain reaction (PCR) analysis.

Regarding limbal stem cell deficiency following phototherapeutic keratectomy.

To the Editor: We found the article “Limbal Stem Cell Deficiency Following Phototherapeutic Keratectomy” intriguing. There are 2 points that need clarification by the authors. Figure 2 is a photomicrograph of a histologic section labeled as an excised “pannus.” This histologic section shows conjunctival epithelium with goblet cells and no inflammation. The text of the article states that there are goblet cells and inflammatory cells present in the epithelium. Neither of these histologic features is diagnostic of a pannus. Although the slit-lamp photos clearly show peripheral vascularization of the cornea, this is not presented to the readership in the photomicrograph. If this overlies the cornea, then it would more accurately be described as conjunctivalization of the cornea. A pannus may be degenerative or inflammatory in nature, and these two types may be present in the same lesion. A degenerative pannus is characterized predominantly by a fibrous membrane beneath the corneal epithelium with minimal subepithelial inflammation and preservation of Bowman’s layer. In an inflammatory pannus there is destruction of the Bowman’s layer and vascularized connective tissue with a chronic inflammatory cell infiltrate present beneath the corneal epithelium. Clearly, this patient has several underlying reasons for epitheliopathy and localized limbal stem cell deficiency. With a history of trauma, recurrent epithelial erosions, diabetes, and rosacea, a localized stem cell deficiency may be related to those disease processes rather than phototherapeutic keratectomy. It is also unclear why the authors delivered several additional laser spots by “passively moving the patient’s head in a circular fashion at constant speed.” To deliver additional laser treatments and perform extensive debridement in areas where there is already a localized stem cell deficiency will only further compromise the limbal stem cells. This case report makes a significant contribution to the medical literature by continuing to raise awareness that all therapeutic maneuvers at the limbus can have a significant impact on the stem cells, and this should be considered in planning surgery.