Schwannoma with features mimicking neuroblastoma: report of two cases with immunohistochemical and ultrastructural findings

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.

Schwannomas and their pathogenesis

Schwannomas may occur spontaneously, or in the context of a familial tumor syndrome such as neurofibromatosis type 2 (NF2), schwannomatosis and Carney's complex. Schwannomas have a variety of morphological appearances, but they behave as World Health Organization (WHO) grade I tumors, and only very rarely undergo malignant transformation. Central to the pathogenesis of these tumors is loss of function of merlin, either by direct genetic change involving the NF2 gene on chromosome 22 or secondarily to merlin inactivation. The genetic pathways and morphological features of schwannomas associated with different genetic syndromes will be discussed. Merlin has multiple functions, including within the nucleus and at the cell membrane, and this review summarizes our current understanding of the mechanisms by which merlin loss is involved in schwannoma pathogenesis, highlighting potential areas for therapeutic intervention.

Neuroblastoma-like schwannoma of lumbar spinal nerve root

Neuroblastoma-like schwannoma is a rare nerve sheath tumor with histological features resembling a neuroblastoma. A comprehensive literature review identified only 10 previous case reports of this condition. The authors present the first reported case of a neuroblastoma-like schwannoma at a spinal nerve root. The patient, a 61-year-old woman, presented with severe pain in the right lower extremity that failed to resolve after conservative management. Magnetic resonance imaging revealed an intradural enhancing lesion extending out of the right neural foramen at L1–2. A right L1–2 hemilaminectomy and facetectomy with gross-total resection of the tumor was performed without complications. Neuroblastoma-like schwannoma was diagnosed based on histopathological examination of the biopsied tumor specimen. A postoperative course of serial examination and imaging was chosen based on a suspected benign postoperative course as in the case of a completely resected schwannoma. The authors present the novel case of neuroblastoma-like schwannoma at a lumbar spinal nerve root and describe the distinguishing pathological features of this rare lesion.

A practical and comprehensive immunohistochemical approach to the diagnosis of superficial soft tissue tumors

Soft tissue tumors include neoplasms of specific and unknown lineages, and, therefore, lineage markers of smooth muscle, skeletal muscle, endothelial, epithelial and Schwann cells have proven useful in everyday practice. However, groups of tumors remain that are defined essentially on grounds of histology; others can be defined by molecular genetic studies. The complex distribution patterns of many antigens and loss of some differentiation antigens in malignant tumors often necessitate the use of panels of antibodies. Optimally such panels should address all significant differential diagnostic alternatives. There is little doubt that numerous new differentiation markers will appear in the future. The evaluation of tumor proliferation, apoptosis, and cell cycle control will give new information related to tumor biology and prognosis.

Primary intrathoracic low-grade fibromyxoid sarcoma

Low-grade fibromyxoid sarcoma (LGFMS) is a rare neoplasm commonly affecting young adults and typically arising in the somatic soft tissue of the proximal extremities. Its occurrence within the thoracic cavity is exceedingly rare. We report an LGFMS arising from the epicardial surface of the right side of the heart in a 44-year-old woman. Diagnosis was aided by a strikingly characteristic light microscopic appearance of a bland spindle cell sarcoma containing numerous so-called giant collagen rosettes and supported by immunohistology, evidence of FUS translocation by fluorescence in situ hybridization, and electron microscopy demonstrating a fibroblastic phenotype. Aspiration cytology showed a nonspecific bland spindle cell lesion. Review of the literature uncovered 5 previously reported examples of intrathoracic LGFMS. Low-grade fibromyxoid sarcoma is probably an underrecognized intrathoracic neoplasm and should be considered in the differential diagnosis of spindle cell neoplasms of the mediastinum, pleura, heart, and lungs.

Collagen-rich variant of benign epithelioid peripheral nerve sheath tumor of the skin

Schwannoma and neurofibroma account for the majority of cutaneous benign peripheral nerve sheath tumors and usually pose little diagnostic difficulty in their classic forms. In rare instances, however, benign peripheral nerve sheath tumors may display epithelioid morphology and lack otherwise usual features of schwannoma or neurofibroma, making classification difficult. These unusual changes may prompt consideration of other benign neoplasms or a malignancy. Benign epithelioid peripheral nerve sheath tumor (BEPNST) is a somewhat non-specific term recently proposed to describe these neoplasms of imprecise histogenesis. Also diagnostically challenging, rare BEPNST with unusual arrangements of extracellular collagen have been described and reported as neuroblastoma-like schwannoma and collagenous spherulosis. We report a unique case of cutaneous BEPNST with a peculiar arrangement of abundant extracellular collagen, different than the previously observed patterns. Specifically, the neoplastic cells in this tumor were nearly obscured by the collagen, which formed large nodules and compressed the majority of the few remaining tumor cells to the periphery of the lesion. This excessive collagen production emphasizes the importance of adequate sampling to ensure a correct diagnosis.

Rosetoid schwannoma (neuroblastoma-like) in association with an anetoderma

BACKGROUND

We report an additional case of an extremely uncommon but distinctive histological variant of benign schwannoma, which was previously designated as neuroblastoma-like schwannoma by Goldblum et al.

METHODS

A 29-year-old woman referred to a 6-year-history of an atrofic macule. Its clinical appearance was similar to that of an anetoderma.

RESULTS

A cutaneous biopsy showed findings consistent with a neuroblastoma-like schwannoma with the following peculiar features: (i) Being fully composed of rosette-like structures. (ii) Association to an anetoderma.

CONCLUSIONS

Because neither the histological pattern nor the type of tumor allows a differential diagnosis with neuroblastoma, we propose the descriptive term of rosetoid schwannoma. And to our knowledge, this will be the first case reported of rosetoid schwannoma associated to anetoderma.

Schwannoma with neuroblastoma-like rosettes: an unusual morphologic variant

In the past ten years, seven cases of schwannomas with giant fibrillar rosettes or perivascular rosettes have been reported. As these unusual variants of schwannomas had areas with hyperchromatic, small round cells recapitulating the appearance of a neuroblastoma, they received the descriptive name of neuroblastoma-like schwannomas. We herein report two additional cases of this unique variant of schwannoma and provide differential diagnostic considerations.

The Big Eye in the 21st century: the role of electron microscopy in modern diagnostic neuropathology

Electron microscopy (EM) remains a powerful and even essential tool in modern diagnostic neuropathology. tumors are still encountered that defy histological or immunohistochemical classification, and EM can often provide answers in these cases. Tumors of the CNS for which EM is useful include unusual or atypical variants of meningioma, ependymoma, and schwannoma; oligodendroglioma-like tumors composed of small "clear" cells; and small "blue cell" tumors of childhood. EM is of great value in identifying site of origin for metastatic adenocarcinomas of unknown origin-an under-recognized and under-utilized potential for this technique. EM is useful in the diagnosis of peripheral nerve sheath tumors and gastrointestinal autonomic nerve tumors. EM is also important in the evaluation of certain congenital, inherited and metabolic diseases-including ceroid lipofuscinoses, CADASIL syndrome, certain myopathies, and mitochondrial encephalomyopathies--and of certain toxic and drug-induced peripheral neuropathies. An important application of EM is its utility in initiating a workup of an atypical tumor or metabolic condition, for which clinical and histological clues point in no obvious direction. In these situations, EM may provide either an answer outright (including answers to questions not asked) or important clues that guide further workup and narrow the range of diagnostic possibilities.