An extracranial CNS presentation of the emerging "intracranial" mesenchymal tumor, FET: CREB-fusion positive

Multidisciplinary treatment of a rare rapidly progressive intracranial myxoid mesenchymal tumor of uncertain differentiation FET-CREB fusion-negative

BACKGROUND

Non-meningothelial intracranial mesenchymal tumors are a heterogeneous group of central nervous system neoplasms endowed with great variability clinically and histologically. For this precise reason, significant difficulties exist in specifically cataloguing tumor entities with such distant characteristics and such uncertain clinical course.

CASE DESCRIPTION

In an attempt to increase the knowledge inherent in this type of central nervous system lesions we report a case of a rare and unusual myxoid mesenchymal tumor of difficult anatomopathological classification characterized by rapid progression and optimal therapeutic response after combined surgical and radiotherapy treatment, with histo-molecular definition and DNA methylation profile. In this case, multidisciplinary management led to timely surgical intervention based on the rapid clinical deterioration and radiological progression; after adjuvant therapy with hadron therapy, the patient has no signs of recurrence two years after the surgical procedure. No FET-CREB fusion was detected, and the DNA methylation profile suggested the presence of multiple chromosomal gains and losses.

CONCLUSIONS

The molecular definition as well the optimal therapeutic regimen of these tumors is not clearly defined yet and analysis of larger series is strongly warranted.

Potential prognostic determinants for FET::CREB fusion-positive intracranial mesenchymal tumor

Intracranial mesenchymal tumor (IMT), FET::CREB fusion-positive is a provisional tumor type in the 2021 WHO classification of central nervous system tumors with limited information available. Herein, we describe five new IMT cases from four females and one male with three harboring an EWSR1::CREM fusion and two featuring an EWSR1::ATF1 fusion. Uniform manifold approximation and projection of DNA methylation array data placed two cases to the methylation class "IMT, subclass B", one to "meningioma-benign" and one to "meningioma-intermediate". A literature review identified 74 cases of IMTs (current five cases included) with a median age of 23 years (range 4-79 years) and a slight female predominance (female/male ratio = 1.55). Among the confirmed fusions, 25 (33.8%) featured an EWSR1::ATF1 fusion, 24 (32.4%) EWSR1::CREB1, 23 (31.1%) EWSR1::CREM, one (1.4%) FUS::CREM, and one (1.4%) EWSR1::CREB3L3. Among 66 patients with follow-up information available (median: 17 months; range: 1-158 months), 26 (39.4%) experienced progression/recurrences (median 10.5 months; range 0-120 months). Ultimately, three patients died of disease, all of whom underwent a subtotal resection for an EWSR1::ATF1 fusion-positive tumor. Outcome analysis revealed subtotal resection as an independent factor associated with a significantly shorter progression free survival (PFS; median: 12 months) compared with gross total resection (median: 60 months; p < 0.001). A younger age (< 14 years) was associated with a shorter PFS (median: 9 months) compared with an older age (median: 49 months; p < 0.05). Infratentorial location was associated with a shorter overall survival compared with supratentorial (p < 0.05). In addition, the EWSR1::ATF1 fusion appeared to be associated with a shorter overall survival compared with the other fusions (p < 0.05). In conclusion, IMT is a locally aggressive tumor with a high recurrence rate. Potential risk factors include subtotal resection, younger age, infratentorial location, and possibly EWSR1::ATF1 fusion. Larger case series are needed to better define prognostic determinants in these tumors.