Intracranial solitary fibrous tumors/hemangiopericytomas: first report of malignant progression

Abstract

OBJECTIVE Meningeal solitary fibrous tumors/hemangiopericytomas (MSFTs/HPCs) are rare intracranial tumors resembling meningiomas. Their classification was redefined in 2016 by the World Health Organization (WHO) as benign Grade I fibrohyaline type, intermediate Grade II hypercellular type, and malignant highly mitotic Grade III. This grouping is based on common histological features and identification of a common NAB2-STAT6 fusion. METHODS The authors retrospectively identified 49 cases of MSFT/HPC. Clinical data were obtained from the medical records, and all cases were analyzed according to this new 2016 WHO grading classification in order to identify malignant transformations. RESULTS Recurrent surgery was performed in 18 (37%) of 49 patients. Malignant progression was identified in 5 (28%) of these 18 cases, with 3 Grade I and 2 Grade II tumors progressing to Grade III, 3-13 years after the initial surgery. Of 31 Grade III tumors treated in this case series, 16% (5/31) were proved to be malignant progressions from lower-grade tumors. CONCLUSIONS Low-grade MSFTs/HPCs can transform into higher grades as shown in this first report of such progression. This is a decisive argument in favor of a common identity for MSFT and meningeal HPC. High-grade MSFTs/HPCs tend to recur more often and be associated with reduced overall survival. Malignant progression could be one mechanism explaining some recurrences or metastases, and justifying long-term follow-up, even for patients with Grade I tumors.

Grading of meningeal solitary fibrous tumors/hemangiopericytomas: analysis of the prognostic value of the Marseille Grading System in a cohort of 132 patients

“…In CNS SFT/HPC, this view might not accurately reflect the particular behavior and the prognosis uncertainty of some of the “benign‐looking” classic fibrous end of the SFT/HPC spectrum. Such tumors may display recurrences and even metastasis during follow‐up . In our cohort, six MGS I tumors (4.5%) recurred after a median follow‐up of 60 months (despite 2 cases with complete surgical resection).…”

“…Long‐term follow‐up is advised for all patients with a meningeal SFT/HPC regardless of grade, because recurrence(s) and/or metastasis can occur several years after initial diagnosis, even following complete surgical resection . It is important to note that such adverse events can also happen for meningeal SFT/HPC with the classic fibrous phenotype . In our cohort, recurrence was observed in eight cases (6%) harboring a classic fibrous phenotype with low mitotic activity (all of which were MGS I) and one of these cases recurred after complete surgical resection.…”

“…Like the 2013 WHO Classification of Tumors of Soft Tissue and Bone , the revised WHO Classification of Tumors of the Central Nervous System regrouped SFT and HPC into a single entity: SFT/HPC. SFTs/HPCs encompass a spectrum consisting of two main phenotypes , but it is important to note that tumors with intermediate morphology or evolution from one phenotype to another are also encountered, often making discrimination between these phenotypes arbitrary . The NAB2‐STAT6 gene fusion and the subsequent nuclear relocation of STAT6, which are both present in the whole spectrum, proved to be highly sensitive and specific for the diagnosis.…”

“…All six patients died of their disease including two cases harboring metastasis. Other examples of tumors with the classical SFT phenotype exhibiting aggressive behavior during long‐term follow‐up have been documented . Recent data suggest late metastatic capacity even for apparently “benign” soft‐tissue SFTs .…”

Pazopanib efficacy in recurrent central nervous system hemangiopericytomas

“…The resulting STAT6positive nuclear staining is the hallmark of the disease, also present in systemic SFT/H [1,2]. SFT/H range from benign grade I fibrohyaline tumors, that are usually surgically removable, to highly aggressive grade III recurrent metastatic lesions: patients need iterative operations in 38-51% of cases and will develop systemic metastases in 10-20% [3,4]. Even though radiation therapy improves progressionfree survival, there is no effective treatment for patients with multiple meningeal lesions not amenable to surgery.…”