Neuronal Elements within Gliomatosis Peritonei: Immunohistochemical Evidence of an Under-Recognized Feature
AY Huang, AW Bollen, CJ Zaloudek. UCSF, San Francisco, CA
Background: Gliomatosis peritonei (GP) is a rare condition in which small nodules of mature glial tissue are found throughout the peritoneal cavity, usually in a patient with concurrent or previous immature ovarian teratoma. Glial implants may be found with or without other teratomatous elements and they may occur within lymph nodes as well as on the peritoneum. While GP is considered to be a benign condition, it can be mistaken for peritoneal carcinomatosis and has been reported to undergo malignant transformation. Recent molecular studies have suggested that glial implants arise from peritoneal cells, presumably pluripotent Mullerian stem cells, rather than from the teratoma. Case reports of non-teratomatous glial implants in patients with a ventriculoperitoneal shunt support the theory that peritoneal cells may be induced to undergo glial metaplasia. Neuronal elements have only rarely been described in reported cases of glial implants and it is unclear whether this is a common finding. It is also unclear whether the presence of neuronal elements might differentiate teratomatous implants from metaplastic implants or provide prognostic information on the malignant potential of the implants. No studies to date have identified neurons with neuron-specific immunohistochemical stains.
Design: Seven cases of gliomatosis peritonei in 6 patients with concurrent or prior diagnosis of immature ovarian teratoma were compiled from our institution (two of the cases were separate surgical specimens from a single patient). Neuronal elements were not previously described within the glial implants in any of these cases. We performed immunohistochemical stains for glial fibrillary acidic protein (GFAP), Neu N, neurofilaments, and synaptophysin on slides with glial implants from the seven cases.
Results: Cells morphologically consistent with neurons were identified in six of the seven cases (representing 5 of the 6 patients) using three neuronal stains (Neu N, neurofilaments, and synaptophysin). The neurons generally had a mature appearance and appeared in clusters within a glial background. One case did not show positive neuronal staining but contained only small foci of GP.
Conclusions: Our findings suggest that neuronal elements are present in many cases of GP but are often overlooked. Further studies to determine whether neuronal elements have any histogenetic or prognostic significance are warranted.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 167, Tuesday Afternoon