Glial papillary tumour of the spinal cord with SMARCB1/INI1-loss and favourable long-term outcome

CNS Low-grade Diffusely Infiltrative Tumors With INI1 Deficiency, Possessing a High Propensity to Progress to Secondary INI1-deficient Rhabdoid Tumors

Atypical teratoid/rhabdoid tumors (AT/RTs) are highly malignant tumors of the central nervous system that predominantly occur in infants, and are characterized by the presence of rhabdoid cells and inactivation of INI1 or (rarely) BRG1. Most AT/RT are identified as primary tumors; however, rare AT/RT or INI1-deficient RTs arising from other primary tumors have been reported. Here, we report 3 cases of hitherto unclassifiable low-grade tumors with loss of INI1 nuclear expression, for which we propose the designation of central nervous system low-grade diffusely infiltrative tumors with INI1 deficiency (CNS LGDIT-INI1), 2 of which progressed to secondary RT. All 3 CNS LGDIT-INI1 exhibited a similar histology: diffusely distributed small tumor cells with round to oval or irregular nuclei and scant cytoplasm were admixed with degenerative neurons and large reactive astrocytes in an edematous, myxoid, or collagenous background. Mitotic figures were absent. Immunohistochemistry revealed that the tumor cells in all 3 CNS LGDIT-INI1 and 2 RT were negative for INI1. Genetically, total or partial homozygous deletions of the INI1 gene were detected in all CNS LGDIT-INI1 and RT excluding 1 CNS LGDIT-INI1 without sufficient DNA quality and quantity. Despite the loss of INI1 expression, these low-grade lesions were clearly distinguishable from AT/RT by their low proliferative activity, diffusely infiltrative growth pattern, and lack of rhabdoid cells and polyphenotypic immunoreactivity. In conclusion, CNS LGDIT-INI1 may represent a rare group of tumors that are clinically indolent but have a high propensity to progress to RT.

Papillary glioblastoma exhibiting a neuroradiological cyst with a mural nodule: A case report

RATIONALE

Glioblastomas are malignant, infiltrating gliomas classified as grade IV by the World Health Organization. Genetically, most glioblastomas do not exhibit the isocitrate dehydrogenase (IDH) 1/2 gene mutation and rarely harbor the 1p/19q co-deletion. Neuroradiologically, glioblastomas rarely form a cyst with a mural nodule lesion.

PATIENT CONCERNS

In this study, a 78-year-old woman, with speech difficulty and forgetfulness, had a cystic tumor with a mural nodule in the right frontoparietal lobe. Therefore, partial tumor resection was performed.

DIAGNOSIS

Histopathology of the tumor, a glioblastoma, exhibited pseudopapillary features with non-hyalinized capillary cores and rich mini-gemistocytic cells. Genetic analysis of the tumor revealed co-deletion of 1p36/19q13, with wild-type IDH.

INTERVENTIONS

The patient underwent a combination of postoperative radiotherapy and temozolomide chemotherapy before leaving the hospital. After discharge, she was treated by 20 courses of temozolomide chemotherapy.

OUTCOMES

The patient is free from tumor recurrence 23 months after the operation.

LESSONS

We present a unique case of glioblastoma that exhibited novel neuroradiological, histopathological, and genetic features with a favorable prognosis for the patient. Therefore, a compilation of similar cases with clinicopathological and genetic analyses to characterize this unique glioblastoma is critical. Clinical evidence will help develop effective therapeutic approaches to improve prognosis in patients with glioblastoma.