11C-MET PET and 18F-FDG PET characteristics of chordoid meningioma

A 17-year-old female patient presented to the neurology department with a 3-month history of left limb numbness and spasm with transient loss of consciousness 3 weeks earlier. A brain MRI revealed a right temporal lobe mass (Figure 1a, arrow) with hypointensity on T1WI, hyperintensity on T2WI, and no diffusion restriction on DWI and ADC mapping. The lesion showed minimal tracer uptake on ¹⁸F-FDG PET (Figure 1b, solid arrowhead) but avid uptake on ¹¹C-MET PET with an SUVmax of 5.7 (Figure 1c, hollow arrowhead) with the contralateral normal tissue as a reference, suggesting a benign tumor other than inflammatory granuloma or malignant tumor. After conservative treatment with hormone and antiepileptic drugs, the patient's symptoms significantly improved. At the 3-month follow-up, the patient presented again with seizures of the left upper limb and transient loss of consciousness. She underwent mass excision in the neurosurgery department. Histopathology (Figure 1d) revealed a neoplasm with cords or trabeculae of small epithelioid to vacuolated cells embedded in a mucin-rich matrix, characteristic of chordoid meningioma (WHO grade 2), a rare type of meningioma [1-3. Immunostaining for SSTR-2 (Figure 1e), EMA, and PR showed strong reactivity in the tumor cells, and the MIB-1 labeling index was about 1%. Postoperative recovery was good, and no positive symptoms were found during a 5-year follow-up period [4]. This case report highlights the need to consider intracranial chordoid meningioma as a differential diagnosis when there is a discrepancy in the extent of tracer uptake on ¹¹C-MET and ¹⁸F-FDG PET [5, 6].

Leilei Yuan: Writing – original draft (Lead). Mengyan Zhang: Writing – original draft (Equal). Li Xu: Resources (Supporting). Xin Wang: Writing – original draft (Supporting). Qian Chen: Writing – review & editing (Supporting). Lin Ai: Writing – review & editing (Lead).

The authors declare no conflicts of interest.

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