Case 2
An 18 years old female, with no addictions or comorbidities, developed an episode of seizure in 2016. Without adequate workup, she was started on phenytoin. The seizures recurred in 2018, while she was on the same anti-epileptic drug. MRI brain done in August 2016 showed a well-defined solid cystic lesion measuring 48x37x46 mm in right parieto-occipital region, with heterogeneous post-contrast enhancement in solid component. Mass effect was seen in form of effacement of adjacent sulci and compression of ipsilateral lateral ventricle. She then underwent surgery with excision of right parieto-occipital lesion, with the post-operative HPR favoring a diagnosis of a peripheral PNET. She was advised to undergo RT, but she never received RT due to some personal reasons, nor did she receive any systemic therapy. She remained asymptomatic for the next five years.
In April 2023, she developed pain in nape of neck, along with vomiting episodes, left sided upper and lower limb weakness. CT scan of brain revealed a heterogeneous space occupying lesion (SOL), measuring 68x49 mm in right parieto-occipital region, with areas of bleed and complex cystic component. Mass effect was seen in form of compression of third and right lateral ventricles and displacement of left lateral ventricle. She underwent surgical resection for the recurrence in September 2023. The HPR showed different diagnosis at three different centres, namely,
  1. embryonal tumor with multilayered rosettes or CNS tumor with BCOR duplication,
  2. WHO grade 2 ependymoma
  3. high grade neoplasm with divergent differentiation.
After surgery, the patient presented to us in February 2024, without having received any adjuvant therapy even this time. Our in-house slide and block review revealed PNET with PanCK, NKX2.2 and EMA positivity, while GFAP, OLIG 2, CK7 and CK20 were negative. MRI brain shown inFigure 6 , revealed a heterogeneously enhancing solid cystic mass in the right parieto-occipital region, measuring 8.3 x 5 x 7.3 cm, underneath the craniotomy site, suggestive of disease recurrence for the second time. Also, a 9.2 x 9.2 mm well-defined enhancing lesion of similar morphology was seen in the right occipital lobe, likely a metastatic deposit. Mass effect was seen as a 6 mm midline shift to left. MR spectroscopy shows absolute choline peak with Choline to N-Acetyl Aspartate ratio 1.7. MR perfusion shows hyper perfusion with relative cerebral blood volume being 1.6. Whole body PET-CT was done to rule out any extracranial source of intracranial PNET, but there was no metabolically active disease noted elsewhere. CSF cytology was also negative.
She underwent Re-do right parieto-occipital craniotomy and near total tumor excision in last week of May 2024. The small occipital lesion could not be tracked with USG and was left behind. Post-operative MRI brain showed stable well-defined enhancing lesion involving the right occipital lobe, with expected postoperative changes in right parietal lobe, as shown in Figure 7 . The postoperative HPR showed a tumor arranged in trabeculae, cords, nests, tubules and rosette pattern, with extensive sclerosis, as shown in Figure 8 . It was composed of round to elongated cells with moderate nuclear pleomorphism and clear cytoplasm. A diagnosis of PNET was made again, with diffuse PanCK, focal EMA, strong complete membranous CD99, NKX2.2 and FLI-1 positivity, and negative staining for GFAP, INSM-1 and synaptophysin. EWSR1 gene rearrangement tested with FISH showed split signals and/or loss of green signals only in 8% tumour cell nuclei, and again it was classified as Embryonal tumour as per WHO CNS Tumour classification 2021 and treatment was decided upon as per High-risk MB protocol. She has been planned for CSI to a dose of 36 Gy in 20 fractions, 1.8 Gy per fraction, followed by radiotherapy boost to residual disease and tumour bed to a dose of 18 Gy in 10 daily fractions, 1.8 Gy per fraction by VMAT technique. The concurrent chemotherapy planned is daily vincristine, 1.5 mg/m2, followed by adjuvant chemotherapy as per Packers A regimen.