A 6‐year‐old boy with left temporal lobe mass

Access at https://isn-slidearchive.org/?col=ISN&fol=Archive&file=ID8033672.R1_1.svs. A 6-year-old boy presented to the neurosurgical department with recurrent episodes of vomiting over the past week. CT imaging revealed an isodense mass measuring approximately 32 × 27 mm with a calcified rim, 7 mm in maximum thickness. The adjacent bony structures were intact and unaffected by the tumor. MRI revealed a well-defined, circular tumor in the parasellar region of the middle cranial fossa, isointense on T1WI, mildly hyperintense on T2WI, with homogeneous, significant enhancement on post-contrast T1WI. The calcified rim at the tumor margins, apposed to the dural surface, showed low signal intensity on T2WI. A non-enhancing, T2WI hyperintense area suggested a possible colloid-like cystic component. No dural tail sign was observed (Figure 1). The patient was subjected to a surgical procedure for the excision of the brain tumor. The tumor appeared grayish-white and firm. Its boundary with the temporal lobe parenchyma was indistinct. Focal calcified components of the tumor had breached the leptomeninges, with adhesions to the dura mater. The tumor was excised along its visible boundaries. Additionally, tissue from the surrounding area, including the sandy-textured peripheral zone and regions with gliotic proliferation, was carefully removed. After the patient's discharge, no further treatment was arranged and follow-up evaluations were scheduled as needed. The intra-operative frozen section revealed a spindle cell tumor with no obvious cellular atypia, hemorrhage, or necrosis. Combined with radiological findings of a solid mass apposed to the dura mater, meningioma was initially considered as a possible diagnosis. Hematoxylin and eosin (H&E) staining showed a prominent fibrous stroma composed of abundant collagen and spindle cells resembling fibroblasts, arranged in a storiform or fascicular pattern, with many areas of calcification (Box 1).Immunohistochemical analysis demonstrated that the spindle cells were negative for EMA, PR, SSTR2, and STAT6, ruling out meningioma and solitary fibrous tumor. In contrast, SOX10, GFAP, and OLIG2 were strongly positive in a subset of cells, confirming the presence of glial components. These glial components showed strong positivity for BRAF V600E immunohistochemical staining, while IDH1 p.R132H was negative and ATRX was positive. The Ki-67 proliferation index was 3%. Only a few synaptophysin-positive neurons were identified after thorough examination of all sections. Next-generation sequencing identified only the BRAF V600E mutation, with no other pathogenic mutations or fusions detected (Figure 2). Desmoplastic infantile ganglioglioma, CNS WHO grade 1. According to the 2021 WHO classification of CNS tumors, desmoplastic infantile astrocytoma/ganglioglioma (DIA/DIG) is categorized as a type of glioneuronal tumor with low invasiveness. This tumor predominantly occurs in early childhood, typically under 2 years old, though non-infantile cases have also been reported. The tumor shows a male predilection, with a gender ratio of approximately 2–1.5:1. The most common clinical presentations include rapidly increasing head circumference, symptoms of intracranial hypertension, and seizures. DIA/DIG are predominantly located in the supratentorial regions, most commonly in the frontal, temporal, and occipital lobes. Vandenberg first described the histological patterns of DIA/DIG in 1987.1 While DIA consists solely of neoplastic astroglia cells, DIG features a mixture of neoplastic astroglial, neuronal, and more primitive neuroepithelial cells. BRAF or RAF1 mutations or fusions are frequently observed in DIA/DIG in absence of CDKN2A/B homozygous deletion, with BRAF V600E mutation frequently reported particularly in non-infantile cases of DIA/DIG, as seen in this case.2 This case aims to present a DIA with atypical features, posing a diagnostic challenge due to its close resemblance to meningioma both in imaging and macroscopic appearance. On imaging, the tumor was relatively limited in size and lacked the typical giant cystic component seen in most DIA/DIG.3 Additionally, rigid peripheral calcifications resembling those associated with meningioma were observed, which are not characteristic of DIA/DIG. Intraoperatively, the tumor was primarily parenchymal in location; however, portions of its calcified components had breached the leptomeninges and exhibited focal adhesions to the dura mater. In addition, the presence of sandy-like tissue surrounding it macroscopically also contributed to the initial diagnostic confusion. In intraoperative frozen sections, spindle-shaped tumor cells can be observed in both meningiomas and DIA/DIG. A thorough analysis of postoperative immunohistochemical staining confirmed the diagnosis of DIG, characterized by the presence of glial markers OLIG2 and GFAP, along with scattered synaptophysin-positive neurons. We hypothesize that the atypical features observed in this case may be partially attributed to the tumor's special location in the middle cranial fossa, where spatial constraints and compression may have influenced its growth pattern. Given the favorable prognosis associated with complete surgical resection, no additional treatment was planned for this patient. The follow-up strategy includes routine evaluations with periodic imaging and clinical assessments to monitor for any signs of recurrence or complications. Kaiyu Liu collected the data and drafted the manuscript; Shilei Zhang and Mengqiu Cao provided essential materials; Renhua Huang, Jiong Hu, Hongda Shao, Yichao Jin, Bingqian Shen, and Hongyu Zhou offered constructive feedback; Lihua Sun and Xiaohua Zhang supervised the study. All authors approved the final version of the manuscript. The case was reviewed and discussed by the neuro-oncology multidisciplinary team at our institute. All team members offered professional support and valuable suggestions for the manuscript. The authors declare no conflicts of interest. Informed consent was obtained from the patient for the publication of this case report and accompanying images. The data that support the findings of this study are available from the corresponding author upon reasonable request.