title: Surgically treated incidentally discovered low-grade gliomas are mostly IDH mutated and 1p19q co-deleted with favorable prognosis.
abstract: OBJECTIVE
  LGGs (low-grade gliomas) are sometimes encountered by chance during radiological examinations. These incidentally discovered LGGs (IDLGGs) were relatively under-studied in the literature. The purpose of current study is to review a cohort of patients with IDLGGs surgically treated in our institution for their clinical and histological aspects and determine their IDH1 and 1p19q status.
  
  
  METHODS
  All patients with hemispheric LGGs receiving operation in our institution between 2001 and 2004 were reviewed. Clinical, radiological and treatment data of the patients were collected and IDLGGs were retrieved and compared with symptomatic LGGs. Histological review was carried out and formalin-fixed paraffin embedded (FFPE) tissues of IDLGGs were examined for IDH1/IDH2 mutation and 1p/19q codeletion.
  
  
  RESULTS
  Twenty three IDLGGs (10.4%) were identified while 196 patients had symptomatic LGGs. The reasons for patients with IDLGGs having radiological examination included trauma (47.8%), dizziness (26.1%), unrelated headache (21.7%), and health checkup (4.4%). Clinically, patients with IDLGGs had higher preoperative KPS (P < 0.001), smaller tumor volume (P = 0.014), lower frequency of eloquent areas involvement (P < 0.001) and higher rate of complete resection (P = 0.037) comparing to those with symptomatic LGGs. Histologically, there is a preponderance of oligodendroglial differentiation with 6 oligodendrogliomas and 11 oligoastrocytomas but there were also 6 astrocytomas. IDH1 mutation and 1p/19q co-deletion were detected in 95.7% (22/23) and 69.6% (16/23) of IDLGGs, respectively. The latter encompassed all but one of the cases of oligodendroglial tumors. Patients with IDLGGs had longer overall survival than those with symptomatic LGGs (P = 0.027).
  
  
  CONCLUSIONS
  We conclude that the majority of IDLGGs are IDH1 mutated and are predominantly oligodendroglial tumors. With a median follow-up of 9.3 years to our series, we conclude that patients with IDLGGs had better prognosis than those with symptomatic LGGs. The favorable prognosis of IDLGGs may be accounted by the higher practicability of extensive resection, non-eloquent tumor location and smaller tumor volume. Frequent IDH1 mutation and 1p/19q co-deletion in IDLGGs may also contribute to the favorable prognosis of this subgroup of patients.
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Zhen-Yu
authors: ZY
authors: Zhang
authors: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong 30-32 Ngan Shing Street, Shatin, N.T., Hong Kong, China.
authors: Aden Ka-Yin
authors: AK
authors: Chan
authors: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong 30-32 Ngan Shing Street, Shatin, N.T., Hong Kong, China.
authors: Ho-Keung
authors: HK
authors: Ng
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Xiao-Jie
authors: XJ
authors: Ding
authors: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong 30-32 Ngan Shing Street, Shatin, N.T., Hong Kong, China.
authors: Yan-Xi
authors: YX
authors: Li
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Zhi-Feng
authors: ZF
authors: Shi
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Wei
authors: W
authors: Zhu
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Ping
authors: P
authors: Zhong
authors: Department of Neuropathology, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Yin
authors: Y
authors: Wang
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Ying
authors: Y
authors: Mao
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Yu
authors: Y
authors: Yao
authors: Department of Neurosurgery, Huashan Hospital, Fudan University 12 Wulumuqi Zhong Road, Shanghai 200040, China.
authors: Liang-Fu
authors: LF
authors: Zhou
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D002872:Chromosome Deletion; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D002888:Chromosomes, Human, Pair 19 / Q000235:genetics; D004252:DNA Mutational Analysis; D005260:Female; D005910:Glioma / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D033162:Incidental Findings; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D053208:Kaplan-Meier Estimate; D008297:Male; D009154:Mutation; D060787:Neoplasm Grading; D011379:Prognosis
chemical_list: C538784:IDH2 protein, human; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human
keywords: Low-grade glioma; incidental; pathology; prognosis; surgery