Desmoplastic myxoid tumour of the pineal region, SMARCB1-mutant is a rare type of pineal parenchymal tumour encountered in adults.
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Epidemiology
Desmoplastic myxoid tumour of the pineal gland SMARCB1-mutant occurs in adolescents and young adults (mean age of diagnosis 40 years old) with a slight predominance in females (M:F ratio of 3:4)1.
Pathology
Its characteristics are still uncertain since the number of cases is limited. Desmoplastic myxoid tumour of the pineal gland SMARCB1-mutant shares with atypical teratoid/rhabdoid tumours (AT/RT) the mutation of the SMARCB1 gene, although it has different histopathological and clinical features 1,2.
Microscopic features
Desmoplastic myxoid tumour of the pineal gland SMARCB1-mutant usually demonstrates spindled and epithelioid cells in a desmoplastic stroma alternating with a myxoid matrix. Unlike atypical teratoid/rhabdoid tumours, it does not present brisk mitotic activity and necrosis 1,2.
Immunophenotype
Similarly to atypical teratoid/rhabdoid tumours, desmoplastic myxoid tumour of the pineal gland SMARCB1-mutant displays loss of nuclear SMARCB1/INI1 protein expression. Ki-67 index ranges from 2% to 15% 1.
Radiographic features
Desmoplastic myxoid tumour of the pineal gland SMARCB1-mutant is indistinguishable from other pineal tumours 2,3.
MRI
T1: hypointense
T2/FLAIR: hyperintense
T1 C+ (Gd): strong enhancement
Treatment and prognosis
Data about treatment and prognosis of the SMARCB1-mutant type of tumour are still limited. Surgical resection is the treatment of choice. Chemotherapy and radiotherapy have been employed in some cases 2.
Differential diagnosis
The differential diagnosis generally includes other pineal parenchymal tumours.