Neuroblastoma‐like schwannoma of the skull base: an enigmatic peripheral nerve sheath tumor variant

Abstract

Neuroblastoma-like schwannoma is an extremely rare histological variant of schwannoma, which histologically mimics a malignant small round cell tumor. Only 19 cases have been reported in the literature to date. We report a case of this tumor located at the skull base in a 44-year-old woman who presented with symptoms of right-sided earache and hearing loss. MRI revealed a large, lobulated, extra-axial mass measuring 8.8 cm × 3.6 cm × 4.2 cm in the floor of the middle and posterior cranial fossa. Microscopic examination revealed a perplexing histopathology with peculiar collagenous rosettes. Differential diagnoses included a broad range of benign and malignant tumors. Typical schwannoma seldom poses a difficulty in diagnosis; however, this unusual variant is a diagnostic challenge which requires an extensive clinico-radiological correlation and immunohistochemical work-up. Hence, knowledge of this entity is a must to avoid erroneous diagnosis and inappropriate treatment.

Neuroblastoma‐like schwannoma with giant rosette: A potential diagnostic pitfall for hyalinizing spindle cell tumor

“…This differential diagnosis is clinically relevant because HSCT is malignant and requires prolonged follow‐up whereas NLS is considered to be a benign neoplasm . Bone erosion, which rarely happens in conventional schwannoma, was extensive in a reported case which lacked histological signs of malignancy . In the literature, nuclear atypia if present is mild and focal and mitotic figures are rarely encountered .…”

“…Thus, our case with 2.6 mm, presents the biggest rosettes up to now. It is worth noting that only four reported cases of NLS showed small rosettes that are really reminiscent of the Homer Wright rosettes, because of their uniform appearance and a roughly unique rim or circular arrangement of lymphocyte‐like cells . Hence, the main differential diagnoses in these cases should be neuroblastoma.…”

“…It is worth noting that only four reported cases of NLS showed small rosettes that are really reminiscent of the Homer Wright rosettes, because of their uniform appearance and a roughly unique rim or circular arrangement of lymphocyte-like cells. 1,3,4,8 Hence, the main differential diagnoses in these cases should be neuroblastoma. However, the cells in NLS are smaller than in neuroblastoma with no significant atypia nor frequent mitotic figures.…”

“…14,15 Bone erosion, which rarely happens in conventional schwannoma, was extensive in a reported case which lacked histological signs of malignancy. 8 In the literature, nuclear atypia if present is mild and focal 2,10 and mitotic figures are rarely encountered. 1,2,8,12 It is worth mentioning that a transformation into an epithelioid malignant peripheral nerve sheath tumor, in an NLS appearing in a patient with a schwannomatosis with a germline SMARCB1 mutation, has been published.…”

“…We conducted a literature review and identified 24 previously reported cases of NLS, predominantly arising in females with a median age of 32.2 years. Cases were mostly located on the limbs although they can involve other areas, including vulva, labial mucosa, orbit, nerve roots, and skull base (Table ).…”