RARE-17. PRIMARY DIFFUSE LEPTOMENINGEAL GLIOMATOSIS OF HIGH GRADE TUMORS

Primary diffuse leptomeningeal gliomatosis(PDLG) of high grade glioma(HGG) is a rarely documented phenomenon observed in less than 5% of glioblastoma(GBM). Purposes of this study are to investigate the clinical outcomes of PDLG of HGG and to analyze the results according to the procedures of operations. We retrospectively reviewed the medical records of 469 patients of HGG at our institute between 2004 and 2019 and 9 of who with PDLG were enrolled in our study. These 9 patients satisfying the condition of Karnofsky performance status ≥70 and Eastern Cooperative Oncology Group performance status ≤2 were conducted the primary surgical biopsy with or without intracranial pressure control. All patients finished the surgery within about 11 days after the detection of leptomeningeal seeding(LMS) on preoperative MRI images and completed the concurrent chemoradiotherapy(CCRT) with temozolomide(TMZ). Among 9 patients, 7 patients started adjuvant temozolomide and 3 patients completed the six cycles of it. 7 patients had done ICP control operation such as ommaya reservoir insertion, extraventricular drainage, and ventriculoperitoneal shunt within 23.3 days after defined as PLDG and survived nearly 10 months. Their pathologic findings were turned out to be seven glioblastomas and two anaplastic astrocytomas. Their median overall survival was 14 months and the 1- and 2-year overall survival rates were 50.8±17.7% and 16.9±15%, respectively. Compared to the 10-year study of GBM in the same institute between 2004 and 2011, in which 67 patients finished with CCRT with TMZ, the median overall survival was 19 months and the 1- and 2-year overall survival rates were 78.3% and 41.7%. The results indicate that PLDG has a worse outcome and overall survival rate is lower than GBM without LMS, so the earlier start of standard CCRT right after aggressive control of increased ICP like conducting CSF diversion might be helpful for the elongation of life expectancy.

Primary leptomeningeal gliomatosis in a domestic shorthaired cat

A 15-y-old neutered male domestic shorthaired cat was presented with a 16-d history of hindlimb paralysis in conjunction with 1-wk duration of inappetence and lethargy. Given intractable clinical signs, development of seizures, and poor prognosis, euthanasia was elected. Gross examination revealed mild, chronic, multifocal intervertebral disk disease; however, no gross abnormalities were noted in the spinal cord. Histologic examination of the cervical, thoracic, and lumbar spinal cord and the myelencephalon revealed diffuse and variable expansion of the meninges by sheets of neoplastic round-to-polygonal cells. The cells formed sheets and clusters, supported by a variably eosinophilic, fibrillar-to-basophilic, homogeneous matrix, and contained a small amount of eosinophilic cytoplasm. The nuclei were round with finely stippled to hyperchromatic chromatin and 1–2 small nucleoli. Mild white matter degeneration was present in the dorsal and ventral funiculi multifocally throughout the spinal cord, but was most severe in the ventral lumbar sections. Immunohistochemistry revealed strong intranuclear immunoreactivity for Olig2, and intracytoplasmic immunoreactivity for glial fibrillary acidic protein, MAP2, and vimentin in the neoplastic glial cells. To our knowledge, primary leptomeningeal gliomatosis has not been reported previously in a cat.