Soft-tissue perineurioma in a 20-year-old patient with neurofibromatosis type 1 (NF1): report of a case and review of the literature

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

Extraneural Sclerosing Perineurioma of the Tongue

Perineurioma (PN) is an uncommon benign peripheral nerve sheath tumor. For the rarity of this tumor in the oral cavity, otolaryngologists and oral surgeons might not be familiar with this entity. Perineuriomas are typically benign and complete excision is deemed adequate management. Thus, their histological recognition is mandatory to avoid unnecessary overtreatment. We report the clinicopathologic findings of an uncommon variant, the Extraneural Sclerosing PN, in an unusual and never described site, the tongue.

A Case of Multiple Perineuriomas in the Colon With Underlying Neurofibromatosis Type I

A 45-year-old woman was referred to us after a positive fecal occult blood test. Colonoscopy revealed a 20-mm polyp in the transverse colon and a 10-mm polyp in the sigmoid colon. Endoscopic mucosal resection was performed as a diagnostic treatment. Both resected polyps were histologically diagnosed as perineuriomas. She was later found to exhibit multiple café-au-lait spots on the skin and subsequently diagnosed as having neurofibromatosis type I (NF-1). Perineuriomas are rare benign peripheral nerve sheath tumors, with no reports of multiple colonic lesions in a patient with NF-1 to date. NF-1 might be associated with the onset of multiple perineuriomas.

Soft Tissue Perineurioma in a Child With Neurofibromatosis Type 1: A Case Report and Review of the Literature

Soft tissue perineurioma is a rare benign peripheral nerve sheath tumor, especially in children. This manuscript presents an unusual case of soft tissue perineurioma in a 10-year-old boy with neurofibromatosis type 1. The patient presented with a lump in the region of the right breast. A subcutaneous, well circumscribed mass was removed. The cut surface was cream with a vaguely nodular appearance. Histology showed a spindle cell lesion with variable architecture and biphasic morphology. There was no nuclear atypia or pleomorphism. The differential diagnosis and other soft tissue lesions that can be seen in neurofibromatosis type 1 are discussed.

Superficial papular neuroma: Case series of a new entity

BACKGROUND

Dermal neural lesions arise in various circumstances and may be difficult to classify.

METHODS

We describe the clinical, histopathologic and immunophenotypic features of a series of terminally differentiated neural lesions not described previously, to our knowledge.

RESULTS

Four cases from men aged 58 to 66 years were included. Some lesions reportedly bled, but no inciting trauma or prior biopsies were reported. None recurred after biopsy, with follow-up ranging from 19 to 113 months. All lesions were papular, with vertically oriented S100-positive spindled cells and nerve fibers in the papillary dermis. Slight epidermal hyperplasia, dilated superficial thin-walled vessels and minimal to mild inflammation were seen in each. Fibers were uniformly fine in 3 cases, with slightly thicker central fibers in the fourth. Three had parakeratotic scale. None were associated with dermal fibrosis or adnexal proliferation. Neurofilament stained axons in each. EMA was negative in all cases. CD34, melan-A and HMB45 were negative when performed.

CONCLUSIONS

We report a small series of benign neural lesions and propose the name "superficial papular neuroma" for this distinct entity. Awareness is important to understand the clinical significance of these lesions and avoid misinterpretation that could lead to overtreatment, unnecessary work-up and increased cost.

Intraoral Pseudo-Onion Bulb Intraneural Proliferations in a Patient with Hemimandibular Hyperplasia: A Case Report and Review of the Literature

This report and review of the literature describes a case of benign intraoral lesions of perineurial origin in a patient with symptomatic hemimandibular hyperplasia causing partial denture soreness. Perineuriomas are a benign peripheral nerve sheath tumor composed of perineurial cells. Intraoral perineuriomas are an extremely rare entity. Two main types of perineuriomas have been described: intraneural and extraneural perineuriomas. A third, similar entity, called an intraneural pseudoperineuriomatous proliferation, has recently been proposed in the literature as a separate and distinctive diagnosis. This report describes the histologic and clinical presentation of intraneural pseudoperineuriomatous proliferations in a patient with hemimandibular hyperplasia.

[Nerve sheath tumours]

Peripheral nerve sheath tumors are common neoplasms in daily practice. Diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer; but on occasion, they are diagnostically challenging (especially with locally aggressive and malignant tumors). This article aims to provide an update of the data (clinical, histological, immunohistochemistry and genomic) of benign, intermediate and malignant peripheral nerve sheath tumors, thanks to the latest WHO "Classification of Tumors of Soft Tissue and Bone", published in 2013, which includes a new chapter on "Nerve Sheath Tumors". Advances in molecular biology have provided new insights into the nature of the various peripheral nerve sheath tumors, and have begun to suggest novel targeted therapeutic approaches.

Microscopic intraneural perineurial cell proliferations in patients with neurofibromatosis type 1

Benign peripheral nerve sheath tumors (PNSTs) showing more than one line of differentiation (hybrid PNSTs) have been increasingly recognized, mainly due to awareness of their existence and as a consequence of increased use of immunohistochemisty during the last decade. Two recent studies suggested overrepresentation of hybrid tumors among benign PNSTs in patients with neurofibromatosis type 1 (NF-1). This study was performed to assess the presence of perineurial cells in microscopic (early) neurofibromatous lesions and normal-looking peripheral nerves in specimens from 5 patients with NF-1 using markers of perineurial cell differentiation (epithelial membrane antigen, claudin-1, and glucose transporter 1). In 2 patients, multiple normal looking nerve fibers as well as hypertrophied nerves and microscopic tumor nodules showed variable intraneural perineurial cell proliferations that frequently occupied the whole nerve fascicle resulting in multiple microscopic reticular perineurioma-like nodules (microscopic hybrid neurofibromatosis/perineuriomatosis). None of the cases showed the onion skin pattern of intraneural perineurioma. However, other nerve fibers within the same specimens showed normal compact rim of perineurium without any detectable intraneural perineurial cells. Both patients had concurrent multiple larger PNSTs (plexiform neurofibromas, hybrid neurofibroma/perineurioma and lesions with features intermediate between the 2 types). One specimen harboring high-grade malignant PNST and 2 specimens with large solitary neurofibromas displayed no intraneural perineurial cells. These observations suggest that intraneural perineurial proliferations are part of the early lesions in the setting of constitutional NF-1 inactivation and support the concept of pure and hybrid perineuriomatous lesions as novel member of the spectrum of PNSTs in NF-1.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Extraneural sclerosing perineurioma of the buccal mucosa: a case report and clinicopathologic review

The perineurioma is an infrequently encountered benign peripheral nerve sheath tumor composed of a clonal proliferation of perineurial cells. Rare cases of perineurioma have been reported in the oral cavity. An extraneural sclerosing perineurioma arising in the buccal mucosa of a 17-year-old male is presented. Histopathologically, the tumor is composed of a well circumscribed nodular proliferation of spindle cells arranged in a storiform growth pattern, in some areas subtly arranged around vascular channels. The tumor cells reveal positive immunostaining for epithelial membrane antigen (EMA), collagen type IV and vimentin, and negative immunostaining for S-100 protein, consistent with a perineurial origin. To the best of our knowledge, this case represents the first report of an extraneural sclerosing perineurioma involving the oral cavity.

Multiple hybrid granular cell tumor-perineuriomas

Hybrid peripheral nerve sheath tumors (PNSTs) are recently recognized, rarely reported entities. Very few hybrid PNSTs with elements of perineurioma have been reported. We report a case of a 47-year-old man who presented with multiple (>20) cutaneous nodules on all 4 extremities, present since childhood. The patient and his family had no history of other PNSTs, other neural-origin tumors, or genetic disorders, including neurofibromatosis. Five excised lesions are well circumscribed but unencapsulated nodular tumors composed of cytologically bland spindled cells with tapering nuclei and indistinct cytoplasm arranged in a storiform pattern in a collagenous matrix. Scattered among these cells are large granular eosinophilic cells. The spindled cells are epithelial membrane antigen-positive and S-100 protein negative. The cytoplasm of the granular cells contains abundant S-100 protein, NK1/C3, and CD68-positive granules. Sparse nerve fascicles contain neurofilament-positive axons. Each tumor also contains poorly marginated areas that histologically resemble pure granular cell tumor, and superficial biopsies of these tumors can histologically resemble pure granular cell tumors. Considering a Schwannian origin for both perineurial and granular cells can provide a logical explanation for the pathogenesis of this case. To the best of our knowledge, our case is the first report of multiple hybrid granular cell tumor-perineurioma.