Intranodal hybrid benign nerve sheath tumor

Hybrid tumors with perineurioma components: a systematic review of the literature and illustrative case

PURPOSE

Hybrid peripheral nerve sheath tumors (HPNST) are a newly recognized class of peripheral nerve sheath tumor, composed of at least two areas characteristic of perineurioma, schwannoma, or neurofibroma. The literature consists only of case reports and small series; therefore, we present an illustrative case and an analysis of all reported cases of HPNST with a perineurioma component in the literature.

METHODS

A systematic search of the literature was performed to identify all reported cases of hybrid perineurioma-schwannoma or perineurioma-neurofibroma in the world's literature. Individual cases were analyzed for demographics, clinical features, imaging, and outcomes.

RESULTS

A total of 159 cases were identified across 41 studies. Hybrid tumors tended to present in mid-adulthood (median 38.5 years), predominantly affected females (57%, 89/156), as a painless (63%, 63/100) mass, or swelling. Ten patients (10/74, 14%) had a history of neurofibromatosis 1, and 2 patients a history of neurofibromatosis 2 (2/74, 3%). The majority (78%, 122/157) of cases occurred superficially, most commonly in the lower extremity (25%, 39/157). Perineurioma-schwannoma was the most reported (86%, 137/159) pathologic diagnosis, with 3 cases presenting with malignant features. Two cases reocurred after resection.

CONCLUSION

HPNST tend to occur in mid-adulthood and present as slowly progressive, painless, superficial masses, with a heterogeneous appearance on imaging. These entities pose a unique diagnostic challenge and likely remain under-recognized in the literature and current clinical practice. They pose low risk of recurrence or malignant transformation, and future work regarding the association with neurofibromatosis and genetic profiles is needed.

Intranodal Neurofibroma: A Case Report and Literature Review

PURPOSE

To report a case of neurofibroma involving the lymph nodes and to perform a literature review on this topic.

OBSERVATIONS

A 72-year-old woman with a history of neurofibromatosis and biopsy-proven malignant melanoma of the left forearm underwent wide local excision of the malignant lesion along with sentinel axillary lymph node biopsy. Histological examination of axillary nodes revealed diffuse neurofibromatosis within 2 lymph node capsules. A thorough review of the English literature pertaining to intranodal neurofibroma was performed by querying Google Scholar and PubMed. Only 5 cases of intranodal neurofibroma have been described until now.

CONCLUSIONS AND IMPORTANCE

Neurofibroma involving the lymph nodes is rare and this is the first reported case that is shown to diffusely involve the intracapsular space. Furthermore, intranodal neurofibroma can represent a diagnostic pitfall in the evaluation of sentinel lymph nodes for metastatic melanoma.

Primary intraosseous hybrid epithelioid schwannoma/perineurioma in the proximal tibia: a case report of benign hybrid neoplasm with local hypercellularity

Background

As a new entity included in the 4th edition of the WHO classification of tumours of soft tissue and bone in 2013, hybrid peripheral nerve sheath tumours are benign composite neoplasms that demonstrate features of more than one type of nerve sheath tumour, with a wide age distribution and a predilection for superficial location. Those involving deep sites are relatively rare. To the best of our knowledge, only one case of primary intraosseous hybrid peripheral nerve sheath tumours has been documented. In this article, we report another case of hybrid peripheral nerve sheath tumours occurring in bone with different clinical, radiological and pathological features from those in the previously reported cases.

Case presentation

A 28-year-old female presented with a painful nodule in the right tibia. Radiological examination revealed an oval eccentric osteolytic lesion in the proximal tibia. Histologically, the circumscribed but unencapsulated lesion demonstrated biphasic cellular differentiation. Bland, small epithelioid cells arranged in clusters in the myxoid or collagenous stroma and inconspicuous spindle cells scattered in the hypercellular areas were suggested to originate from Schwann cells according to the detection of S100. Both the elongated spindle cells with thin, wavy nuclei and the spindle cells in fascicular or storiform pattern in hypercellular areas showed a positive immunoreaction for epithelial membrane antigen, indicating perineurial differentiation. Based on histological and immunochemical examinations, the patient was diagnosed with hybrid epithelioid schwannoma/perineurioma. The lesion was resected and has not recurred for 8 months since resection.

Conclusion

The present case is the second primary intraosseous hybrid peripheral nerve sheath tumour to be reported. This is also the first reported intraosseous tumour composed of epithelioid schwannoma and perineurioma with hypercellularity, indicating diverse involvement sites and a wide range of histological features among hybrid peripheral nerve sheath tumours. Awareness of such diversity is critical for accurate diagnoses. The morphological overlap with other spindle and epithelioid cell neoplasms, especially pure peripheral nerve sheath tumours, requires that immunochemical and molecular examinations be used as objective tools to provide the necessary information for a differential diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13000-019-0829-x) contains supplementary material, which is available to authorized users.

Hybrid peripheral nerve sheath tumors: report of five cases and detailed review of literature

BACKGROUND

Hybrid peripheral nerve sheath tumors (PNSTs) have been recognized recently and were first included in the 4th edition of World Health Organization (WHO) Classification of Tumors of Soft tissue and Bone, published in 2013. These tumors show combined features of more than one type of conventional benign peripheral nerve sheath tumors. The most common combinations are those of schwannoma/perineurioma followed by combinations of neurofibroma/schwannoma and neurofibroma/perineurioma. A detailed literature review of published cases is presented. We have discussed the types and etiology, epidemiology and sites of localization, gross and microscopic appearances and immunohistochemical features of hybrid PNSTs and association of these tumors with tumor syndromes.

CASE PRESENTATION

We have included five cases which were diagnosed in our department as we believe that publication of these new cases is relevant for the improved understanding of these specific tumors. Four of our five patients were males, mean age was 24 years. There was wide variation in the location of these tumors. Mean size of excised tumors was 5.5 cms in the greatest dimensions. Three out of five cases represented hybrid schwannoma/perineurioma histologically. No significant nuclear atypia, mitotic activity or necrosis seen. All five cases were completely excised. All five patients are alive and well at the time of writing with no recurrence.

CONCLUSION

Hybrid PNSTs are distinct tumors and are usually benign. However, rare case reports have described local recurrence and at least two recent case reports have described malignant transformation in these tumors. Further studies on large number of cases are required to determine the exact pathogenetic basis of these tumors.

Mesenteric intranodal schwannoma: uncommon case of neurogenic benign tumor

Intranodal schawnomas are extremely rare. Just a few cases have been described before. Clinical presentation comprises not only symptomatic mass in several anatomical body parts, but also, they can be found during analysis of surgical specimens resected for other reasons. The report is based on the case of an 80-year-old patient who underwent to right hemicolectomy for an adenocarcinoma. The histopathologic analysis revealed one mesenteric intranodal schwannoma in the surgical specimen. The diagnosis was confirmed by immunohistochemistry with positive result for vimentin and S100 protein. Less than 12 cases have been reported in the literature before. The findings pointed out our patient as, one of these few reported with such diagnosis.

24-year-old woman with an internal auditory canal mass. Hybrid peripheral nerve sheath tumor with schwannoma/perineurioma components

Benign peripheral nerve sheath tumors are divided into schwannomas, neurofibromas and perineuriomas. In recent years, tumors with hybrid features, composed of multiple, discrete areas of different histological types, were described. These tumors may represent a diagnostic challenge. A 24-year-old woman with multiple sclerosis was found to have a 1.3 cm TV × 0.7 cm AP T2 intermediate lesion within the left internal auditory canal. Gross examination revealed a tan-white, well circumscribed mass. Histologic examination demonstrated a well demarcated, cellular, solid neoplasm with a biphasic pattern. Most of the tumor was composed of spindle cells arranged in fascicles with focal Verocay body formation and diffuse S100 positivity. A second, minor area showed concentric proliferation of neoplastic spindle cells around one or more axons. Tumor cells in this area were positive for perineurial markers, claudin-1 and Glut-1, and focally immunopositive for CD34.We present here a case of a benign peripheral nerve sheath tumor with histological and immunohistochemical features consistent with a dual pattern of differentiation of schwannoma and perineurioma, in the VIIIth cranial nerve. This is, to our knowledge, the first case of a hybrid perineurioma/schwannoma reported in a cranial nerve.

Hybrid schwannoma/perineurioma: report of 10 Chinese cases supporting a distinctive entity

Hybrid schwannoma/perineurioma is a recently described benign nerve sheath tumor that typically manifests as a dermal tumor on the extremities and trunk. Occurrence outside the skin is uncommon. This article describes 10 cases of hybrid schwannoma/perineurioma arising in diverse anatomic locations. They all occurred in adult patients (age range 27-81 years, median 35 years) with a marked female predominance (2 males and 8 females). Of the 10 tumors, 7 were situated in the subcutis of trunk (n = 3), extremities (n = 2), neck (n = 1), and labium majus (n = 1) and 3 in the submucosa of nasal cavity, sigmoid colon, and rectum, respectively. Histologically, they were composed of intimately admixed plump spindle cells and elongated slender spindle cells forming storiform, lamellar or fascicular architecture. By immunohistochemistry, the tumor showed dual differentiation of schwannian cells (plump-spindled) and perineurial cells (slender-spindled), characterized by strong S100 protein expression in the former component and variable immunoreactivity of epithelial membrane antigen, claudin-1, and CD34 in the latter. Awareness of its morphological characteristics and potential occurrence in diverse sites may aid in the recognition of this rare tumor type.