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

Neuroblastoma-like schwannoma (NLS) is a rare variant of a common tumor. The aim of this study is to discuss, through a literature review, the differential diagnoses of NLS while emphasizing the importance of ancillary studies. So far, 24 cases have been reported. We describe an additional case in a 64-year-old woman who had a 3-cm subcutaneous tumor on her flank. The histological examination showed an encapsulated neoplasm. Most of the tumor was made of giant rosettes. These rosettes had several sizes reaching 2.6 mm. They showed a palisade of rounded cells. Nuclei were hyperchromatic but bland. The center was made of eosinophilic cores of collagenous radiating fibrils. Neoplastic cells stained strongly for S-100 protein. In the capsule, perineural cells stained for epithelial membrane antigen (EMA). No expression of Mucin 4 (MUC4) was present. This was consistent with NLS. The same peculiar appearance of giant rosettes has been described in hyalinizing spindle cell tumor with giant rosettes (HSCT). We propose the term "neuroblastoma-like schwannoma" when there are small rosettes, "HSCT-like schwannoma" for tumors with giant rosettes and "collagen-rich schwannoma" when there are "ill-defined" structures reminiscent of rosettes. Immunohistochemical panel containing S100, EMA, and MUC4, as well as molecular testing when needed should be performed.

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

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 in a case of schwannomatosis: Report of a rare case.

Schwannomatosis is a term used to describe patients with multiple nonvestibular schwannomas with no other stigmata of neurofibromatosis type-2 (NF2). Neuroblastoma-like schwannoma is a rare subtype of schwannoma, with histological features resembling a neuroblastoma. This case is probabaly the second case of very uncommon neuroblastoma-like schwannoma, in a patient of schwannomatosis.

Pleural-based neuroblastoma-like schwannoma: a case report with cytologic findings and review of literature.

We report a rare case of a 45-year-old African American woman with Neuroblastoma-like Schwannoma (Neurilemmoma) occurring in the posterior mediastinum as a pleural-based mass noted on computed tomography (CT) scan. A CT-guided core biopsy of the mass was performed and core biopsy imprints were prepared during the procedure. A Diff-Quik stain was performed for on-site evaluation of specimen adequacy. The hematoxylin and eosin (H&E) staining was evaluated subsequently. Immunohistochemistry panels were applied to the same specimen. The cytologic findings of the core biopsy imprints showed hypercellular smears with a predominance of small cells with atypical features including hyperchromatic, round nuclei and occasional nucleoli. Neurocytic rosettes were particularly appreciated on H&E stain. The immunohistochemical results exhibited strong and diffuse immunoreactivity for S-100 and vimentin. This case enriches the cytopathology literature by providing awareness of this tumor presenting as a posterior mediastinal mass.