Recurrent glioblastoma diagnosed by fluorescence in situ hybridization for EGFR.

Glioblastoma (GBM) continues to be the most common primary brain tumor in adults with a rapidly progressive and fatal course despite current therapies. The molecular genetics of these tumors are being intensely investigated and diVerent types of genetic pathways are seen within two types of GBMs: de novo (or primary) GBMs often show epidermal growth factor receptor (EGFR) gene ampliWcation and overexpression, p16INK4A deletion, and deletions on chromosome 10 (PTEN) while secondary GBMs may show TP53 and RB mutations. However, to date, none of these molecular markers have been shown to predict patient prognosis independent of age and histological grade. After the initial diagnosis of GBM, most patients undergo surgical resection followed by radiotherapy and/or chemotherapy. Occasionally a biopsy is performed to distinguish radiation necrosis from recurrent tumor. The interpretation of these biopsies is diYcult as these interventions are all accompanied by macrophage inWltrates, vascular changes, and variable degrees of necrosis which may be intense. We recently undertook to evaluate such a needle biopsy using Xuorescence in situ hybridization (FISH) for the EGFR locus on chromosome 7 using the formalin Wxed paraYn embedded needle biopsy specimen from a patient with a GBM. Our Wndings indicate that, in selected cases, FISH for EGFR is a powerful method to identify and diagnose recurrent GBM. A 54-year-old man initially presented to an outside hospital with Xu-like symptoms, headache, and leftsided weakness and was found to have a brain lesion in the right occipital lobe. The tumor was resected at the outside hospital and diagnosed as a GBM with small cell morphology (Figs. 1a, b). The patient had resolution of symptoms following surgery. A follow-up MRI imaging of the brain showed possible residual tumor with a nodular marginal enhancement surrounding the previous resection cavity as well as a separate nodule of enhancement identiWed superior to the resection cavity measuring approximately 10 £ 9 £ 7 mm. Approximately 3 weeks after his initial surgery, he underwent a repeat craniotomy with Rickham reservoir placement at Duke University Medical Center. His follow-up therapy at Duke University Medical Center included initiation of radiolabeled monoclonal antibody treatment. Microscopic examination from the patient s second resection demonstrated brain tissue with a dense population of cells (Fig. 1c). HAM-56 immunostaining, a marker for macrophages and endothelial cells [Am J Surg Pathol 1992; (5):493–499] showed that the macrophage population in the biopsy accounted for at least 50% of the cells in the section (Fig. 1d). These cells were associated with an intermixed population of glial Wbrillary acidic protein (GFAP) positive, small astrocytes usually with elongated, complex processes suggestive of reactive astrocytes. Slightly atypical nuclei are also seen (Fig. 1e). The Ki-67 labeling index was brisk, but because of the signiWcant macrophage population, its signiWcance was unclear. A diagnosis of “Hypercellular brain with marked macrophage inWltrate” was rendered with the comment that it was not clear that the intermixed glial population M. N. Grunkemeier (&) · K. Turner · R. E. McLendon Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, NC 27710, USA e-mail: natalie.grunkemeier@duke.edu