Plexiform and other unusual variants of palisaded encapsulated neuroma

Treating Trigeminal Schwannoma through a Transorbital Approach: A Systematic Review

Background: Trigeminal schwannomas (TSs) are uncommon tumors found along any segment of the fifth cranial nerve (CN V). Typically located at the skull base, these benign tumors carry substantial morbidity due to the extent of traditional surgical methods. Minimally invasive endoscopic surgery such as the endoscopic transorbital approach (ETOA) presents promising new avenues for treatment, with the transorbital approach emerging as a potentially successful alternative. Methods: This review systematically assesses the application of the ETOA in treating TSs. PubMed, Ovid MEDLINE, and Embase were thoroughly searched for articles detailing the use of the ETOA in clinical case studies. The outcomes of interest encompassed epidemiological profiling, surgical results, and complication rates. Results: This study included 70 patients with TSs (from six studies), with 22 males (31.4%) and 58 females (68.6%). Patients averaged 55 years and were monitored for around 16.4 months (on average). In most tumors, the middle cranial fossa was involved to some degree. The majority (87.2%) were large (3-6 cm) and underwent gross total resection (GTR) or near-total resection in 87.2% of patients. Preoperatively, sensory alterations were common, along with proptosis, neuropathic pain, and diplopia. Postoperatively, complications included ptosis, diplopia, sensory impairment, corneal keratopathy, masticatory difficulty, and neuralgia. The pure ETOA was the primary surgical technique used in 90% of cases, with no recurrence observed during the follow-up period. Conclusions: Using the ETOA to treat TSs demonstrated an oncologic control rate of 87.2%. Postoperative complications including ptosis, diplopia, and sensory disturbances have been observed, but careful monitoring and management can mitigate these problems. The ETOA emerges as a viable surgical option, especially for tumors involving the middle cranial fossa, capable of adapting to individual patient needs and demonstrating efficacy in TS management.

Oral palisaded encapsulated neuroma; a diagnosis seldom suspected clinically

Key Clinical Message

Palisaded encapsulated neuroma (PEN) is generally seen in the head and neck area as an asymptomatic nodule with the same color as the surrounding skin and rarely occurs in the oral cavity. The exact etiology of PEN is not known, but there is evidence supporting the role of trauma as its etiological factor.

Abstract

Palisaded encapsulated neuroma (PEN) is one of the benign nerve sheath tumors of Schwann cell origin, which is commonly found in the skin of the head and neck area, and rarely occurs in the oral cavity. Its exact etiology is unknown, but there is evidence that supports the role of trauma as an etiological factor. Here we present a case of PEN in the hard palate of a 30-year-old patient and review the differential diagnoses of these nerve sheath tumors of the oral cavity.

Multiple Cutaneous Solitary Circumscribed Neuroma in a Patient with Neurofibromatosis Type 2: An "Incidentaloma" or New Association?

Solitary circumscribed neuroma formerly known as palisaded encapsulated neuroma is a rare, benign neural tumor that usually presents as a painless firm nodule or papule on the face and within oral cavity, although they can occur elsewhere on the body. No association with neurofibromatosis has been reported in the literature. Herein, we report, a previously unreported unique association of neurofibromatosis type 2 (NF-2) with multiple cutaneous solitary circumscribed neuromas in a 24-year-old female. A 24-year-old female with history of NF-2 presented with two slow-growing soft-to-firm papules on the chin and forehead that had been gradually increasing in size over a period of 5 years. The papule on the chin was increasingly tender to palpation. Histologic sections demonstrated a dermal based almost encapsulated, smoothly contoured tumefactive mass composed of spindle cell proliferation with neuroid structures and foci of palisaded growth (resembling schwannoma) and intralesional cleft like spaces. By immunohistochemistry, the lesional cells were strongly and diffusely positive for S-100 and SOX10 with multifocal neurofilament expression while the "capsule" was diffusely reactive for epithelial membrane antigen. The overall features were considered prototypic for solitary circumscribed neuroma. The patient is 18-months post-surgical resection with no evidence of recurrence. In summary, we report for the first time a case of multiple solitary circumscribed neuromas in a patient with known NF2. We highlight pertinent diagnostic clues relevant to surgical pathologist to facilitate recognition (as this tumor is often mistaken for schwannoma or neurofibroma). The clinical behavior is excellent and surgical resection is considered curative.

A Giant Schwannoma Extending from Medial Portion of Middle Cranial Fossa to Parapharyngeal Space and Deep Parotid Space

Trigeminal schwannomas are rare tumours comprising 0.2% of all intracranial tumours and 0.5% of all head and neck tumours. Patients with trigeminal schwannomas presented with facial hypoesthesia and pain. We presented a case with left bulging oropharynx. The CT scan showed a 3.8x2.6x4.9cm left parapharyngeal tumour compressed to the oropharynx and middle cranial fossa. We performed 3 ways in two times of operation to excise the whole tumour. We chose the transoral approach for parapharyngeal space, trans-parotid approach for deep parotid part and the endoscopic endonasal trans-pterygoid approach and trans-maxillary with Canine fossa trephination for intracranial lesions. The pathology showed schwannoma. A huge schwannoma extended from intracranial to several spaces is difficult to resect just by one approach. We should separate the tumour to several parts by clinical image before the operation and design a plan to remove the whole tumour in different approach. The different space of tumour involvement had several ways to access. We needed to choose the less harm but with better surgical field.

Acral multiple symmetrical palisaded encapsulated neuromas: A rare case report and review of the literature

Palisaded encapsulated neuroma (PEN) is a benign neoplasm composed of nerve tissue. It typically presents as isolated, asymptomatic, skin-colored papules or nodules on the face, neck, or oral mucosa of the middle-aged and elderly. Here, we reported a very unusual and unique case of acral multiple symmetrical PENs with no obvious systemic abnormalities and reviewed the published work on acral PEN.

Plexiform Schwannoma of the Oral Cavity: Report of Eight Cases and a Review of the Literature

Plexiform schwannoma represents an unusual schwannoma variant, characterized by multinodular growth grossly and/or microscopically. A review of the English-language literature reveals only 28 previously reported cases involving the oral cavity, and herein we present 8 additional cases. Among these 36 patients, the average age at diagnosis was 28 years (range 5 to 62 years), with a female-to-male ratio of 1.4:1. The most frequently involved sites were the tongue (n = 13) and lip (n = 11). Lesion duration prior to presentation averaged 5.3 years (range, 6 weeks to 26 years). The average lesion size was 2.1 cm (range, 0.3 to 16 cm). The typical clinical presentation was a painless mass, although infrequent findings included pain/discomfort, paresthesia, difficulty chewing, and limited buccal mobility. All cases clinically appeared as a solitary mass or localized cluster of tumor nodules, with the exception of one patient who had neurofibromatosis 2 (NF2) and exhibited two distinct nodules on the tongue and buccal mucosa. In addition, extraoral neural neoplasms were evident in four patients, including three with NF2. Typical microscopic findings included multiple well-circumscribed tumor nodules, each surrounded by a perineurium-derived capsule with immunoreactivity for epithelial membrane antigen. The nodules contained characteristically bland and diffusely S-100-positive spindle cells arranged in Antoni A and B patterns; however, modest nuclear pleomorphism was evident in three cases. Most patients (n = 23) were treated by excision or enucleation and curettage, and three patients experienced recurrence. Unlike plexiform neurofibromas, plexiform schwannomas exhibit only a weak association with neurofibromatosis and have no known malignant potential.

Hypercellular Encapsulated Neuroma Imitating Desmoplastic Melanoma

Palisaded encapsulated neuromas (PENs) are benign cutaneous nerve sheath proliferations that typically occur as flesh-colored papules solitarily on the head and neck in adults, with a slight predilection for females. Histopathologically, they are partially or completely encapsulated intradermal nodules with Schwann cells and axons in fascicles separated by clefts. Although these features are often characteristic, the hypercellular variant of PEN can pose a diagnostic challenge in distinguishing between other cellular neural and melanocytic lesions. We herein report a case of hypercellular PEN, which showed striking similarity to desmoplastic melanoma.

Palisaded Encapsulated (Solitary Circumscribed) Neuroma: A Review of 30 Cases

Background. Solitary circumscribed neuroma (SCN), also known as palisaded encapsulated neuroma (PEN), is a benign neural tumor. It may be mistaken as either schwannoma or neurofibroma in pathology practice. In this study, we aimed to define clinicopathologic and immunohistochemical features and discuss its differential diagnosis. Materials and Methods. The histopathological features of 30 cases of SCN/PEN were reviewed. The presence of intralesional axons, Schwann, and perineural cell distributions were investigated by performing neuronal immunomarkers. Results. Twelve cases were females, and 18 cases were males. The mean age was 48 years. Lesions were mostly located on the face (27/30). Histologically, 18 had a lobular pattern, 9 were plexiform, 2 fungating, and 1 multilobular. Although the majority of cases were well circumscribed, capsular integrity was at least focally disrupted (73%). Verocay body was noted only in 6 cases (20%). One case showed excessive hyperkeratosis, forming a keratin horn. Adipocytic change was detected in another case. The lesions consisted of S100-positive Schwann cell proliferation and were partially surrounded by perineural cells highlighted by EMA or Claudin-1. The amount of intralesional axons revealed by neurofilament immunostaining was variable. Conclusion. SCN/PEN is a relatively common lesion, and usually seen as an asymptomatic papule on the face of elderly patients. A circumscribed lesion composed of bundles of bland-looking spindle cells thought to be of neural origin is seen in the dermis. Pathologists should be aware of the existence of plexiform and multilobular PEN/SCN variants, to avoid misdiagnosis of plexiform neurofibroma or schwannoma.

Palisaded Encapsulated Neuroma: An Unusual Presentation

Palisaded encapsulated neuroma (PEN) is a distinctive benign neural tumor, which usually presents as a solitary skin-colored papule or a nodule. It is a benign lesion and may clinically mimic a cutaneous neurofibroma, melanocytic nevi, or cutaneous schwannoma. Here we report a rare case of multifocal cutaneous PENs and its differentiation from cutaneous schwannomas, which is possible by histopathology.

Trigeminal schwannoma

Schwannoma is a benign tumor of the nerve sheath arising from the perineural schwann cells. The nerves most commonly involved in schwannomas of the head and neck are the vagus and the cervical sympathetic chain. Trigeminal schwannomas are rare tumours. A 17 year old male patient with a chief complaint of swelling on face was diagnosed as suffering from bening tumor extending from cranial base (from foramen ovale) to the parapharengeal space. Mandibular access osteotomy was done to expose the tumor. Surgical excision of the tumor was done along with the preservation of the nerve. Schwannomas can occur along the pathway of any somatic or sympathetic nerve. Superficial schwannomas require simple exposure and excision but the one which are deep and large, may require complex access osteotomies. Careful surgery is required to preserve the nerve function. Once completely excised, the prognosis is excellent.

Acral Plexiform Palisaded Encapsulated Neuromas as the Initial Cutaneous Manifestation of Cowden Syndrome

Cowden syndrome (CS) is an autosomal dominant genodermatosis associated with characteristic mucocutaneous findings of facial trichilemmomas, palmoplantar keratoses, sclerotic fibromas, and oral papillomas. Mucocutaneous neuromas have also been reported in association with CS. We describe a patient with CS whose sole cutaneous finding was palisaded encapsulated neuromas (PENs) with a plexiform growth pattern in an acral location. Along with previous reports, this case suggests that acral plexiform PENs may be an early, highly specific finding in CS and highlights the importance of screening these patients for PTEN mutation.

Extracranial Trigeminal Schwannomas: A Retrospective Analysis

OBJECTIVE

To analyse the clinic-radiological features and treatment outcome of extracranial trigeminal schwannomas.

METHOD

Medical records and radiographs of patients treated, from January 2011 to December 2013, for neurogenic tumors were retrospectively reviewed. Extracranial schwannomas other than those of trigeminal nerve were also excluded. A number of parameters, including the patient's age, gender, site, clinical features, radiographic features, histologic variants and treatment provided as well as any associated complications were recorded and analysed.

RESULT

A total of 5 patients met the inclusion criteria. The patients were males, aged 16-56 years. All the schwannomas appear to originate from the terminal branches of trigeminal nerve.

CONCLUSION

Long standing asymptomatic swelling of cheek should include trigeminal schwannomas as the differential diagnosis. The diagnosis though confirmed by the histologic examination but can also be made on the basis of MRI finding. Neural function can be preserved by meticulous surgery.

Zosteriform palisaded encapsulated neuroma: an unusual presentation

Palisaded encapsulated neuroma (PEN) is an infrequent benign cutaneous neural tumor, which usually presents as solitary, asymptomatic, papule or nodule, often localized on the faces, around the orifices, in middle age with no sex preponderance. Rarely, it can be multiple. Both solitary and multiple lesions are not associated with neurofibromatosis or multiple endocrine neoplasica syndrome type 2B (MEN 2B). We hereby report, a rare case of multiple cutaneous PEN in a 30-year-old female who presented with multiple asymptomatic soft-to-firm papules and nodules in a dermatomal distribution on the face along the supply of the ophthalmic division of the trigeminal nerve with no signs of neurofibromatosis or MEN 2B.

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.

Palisaded encapsulated ("solitary circumscribed") neuroma of the oral cavity: a review of 55 cases

We describe the clinicopathologic characteristics of 55 oral palisaded encapsulated (solitary circumscribed) neuromas (PEN/SCN). Fifty-five cases of PEN/SCN in 54 patients were reviewed. Lesions were categorized according to their histologic pattern, partial or complete encapsulation, presence of Verocay bodies and presence of a parent peripheral nerve. In 13 selected cases immunohistochemical evaluation for neuronal markers (S-100, GFAP, NFP, EMA) was performed. When immunoreaction with EMA was weak, claudin-1 and glut-1 stains were utilized. Thirty-eight patients were men and 16 were women. Mean patient age was 48 years (SD: +/-14). The vast majority involved the masticatory (palate and gingiva) mucosa (76.4%) followed by the labial mucosa, the tongue and buccal mucosa. Recurrence was recorded in only one case. Histologically, 34 lesions had a lobular pattern, 10 were plexiform, 7 fungating and 4 multilobular. Stroma was limited, but focal myxoid changes were seen at the periphery of the lobules. Only one predominantly myxoid lesion was encountered. The number of intralesional axons varied, but the ratio of Schwann cells to axons was generally less than 1:2. Most lesions (89%) were only partially surrounded by perineurium. Tumor cells were S-100 positive and GFAP negative. The parent nerve was identified in 50% of the cases. Overlying epithelium was generally atrophic. Peritumoral connective tissue was generally unremarkable, but chronic inflammation was present in five cases. PEN/SCN is a relatively common peripheral nerve sheath tumor. Generally, its diagnosis is simple. GFAP may be of help to distinguish PEN/SCN from other peripheral nerve sheath tumors (schwannoma, neurofibroma, traumatic neuroma) in cases where histomorphologic features may be confusing. Finally, pathologists should be aware of the occurrence of plexiform and multilobular PEN/SCN variants, to avoid misinterpretation as plexiform neurofibroma or schwannoma.

Unusual Benign Myxoid Nerve Sheath Lesion: Myxoid Palisaded Encapsulated Neuroma (PEN) or Nerve Sheath Myxoma With PEN/PEN-like Features?

A 38-year-old woman had a polypoid nodule on her scalp. The lesion histopathologically demonstrated an extensive myxoid lobular lesion associated with a nonmyxoid and cellular area in the peripheral area of the lesion. The features of the peripheral cellular area resembled those of palisaded encapsulated neuroma (PEN). Most of the lesion was myxoid, with a large lobule in which several thin fibrous septa were present, dividing it into smaller lobules. The myxomatous area was composed of spindle cells or stellate cells with elongated cytoplasmic processes. There was a loose cellular network with a reticular and netlike network pattern or a lamellar pattern. From the immunohistochemical findings, as well as the histopathologic features, the whole lesion was thus considered to be a PEN, whereas the main, myxoid, lobular lesion was thought to have been caused by myxoid changes within a PEN, namely, myxoid PEN. It cannot be completely ruled out, however, that this case could be that of a nerve sheath myxoma with a PEN/PEN-like lesion. Thus, the present case may suggest that PEN can show extensive myxoid change or may demonstrate a relationship between PEN and nerve sheath myxoma.

Multiple cutaneous neuromas and macular amyloidosis associated with medullary thyroid carcinoma

Multiple cutaneous neuromas are rarely seen in dermatology practice. We report a case of multiple cutaneous neuromas, macular amyloidosis (MA), and medullary thyroid carcinoma (MTC) and discuss the interrelationship of the associated conditions. Multiple endocrine neoplasia 2 (MEN 2) is a hereditary syndrome that comprises MEN 2A, MEN 2B, and familial MTC. Germline mutations in the RET proto-oncogene is the underlying cause of the syndrome. MEN 2A and MEN 2B show some common endocrine manifestations including MTC and pheochromocytoma. There are reports of families with MA and MEN 2A. Multiple mucosal neuromas occur in 100% of patients with MEN 2B syndrome. Cutaneous neuromas are infrequently reported in MEN 2B syndrome. Our patient was a heterozygote carrier of GAG-->GAC mutation (Glu 768 Asp) in exon 13, codon 768 of the RET proto-oncogene. We speculate that our patient may represent an unusual presentation of MEN 2B or an overlap of MEN 2A and MEN 2B syndromes or a sporadic MTC case with unusual associations.

Recurrent multinodular neurilemmoma of the female upper lip

Neurilemmoma is the most commonly encountered nerve sheath tumour of the oral cavity. It generally appears as a single encapsulated nodule. The tongue is involved most frequently and the lip rarely. The tumour is usually uninodular. Multinodular neurilemmoma of the upper lip is very rare and has been reported in only one patient. This is the first reported case of multinodular neurilemmoma in the upper lip of a female.

Reticular and plexiform perineurioma: clinicopathological and immunohistochemical analysis of two cases and review of perineurial neoplasms of skin and soft tissues

Perineurioma represents a recently described and relatively rare neoplasm in the spectrum of benign peripheral nerve sheath tumours composed of perineurial cells staining immunohistochemically positive for epithelial membrane antigen (EMA). In addition to intraneural, extraneural and sclerosing perineurioma, rare variants of perineurioma may occur, and their knowledge is important in the differential diagnosis of mesenchymal tumours of different lines of differentiation and clinically more aggressive neoplasms. We present a case of deep-seated reticular perineurioma arising on the upper arm of a 34-year-old female and a case of a dermal plexiform perineurioma arising on the lower lip of a 60-year-old female. The diagnosis was confirmed in both cases immunohistochemically; neoplastic cells stained positively for EMA and for the newly described perineurial markers, claudin-1 and glut-1. The morphological spectrum and the differential diagnosis of perineurial neoplasms of skin and soft tissues are discussed.

Intraneural dendritic cell neurofibroma with pseudorosettes

Dendritic cell neurofibroma with pseudorosettes (DCNWPR) is a recently proposed variant of neurofibroma. However, its peripheral nerve sheath origin has subsequently been questioned, and it has been suggested that the neoplasm could represent a hitherto undescribed variant of melanocytic nevus with neural differentiation. Here we report a case of DCNWPR that arose almost exclusively within the confinement of the perineurium in the skin. This observation gives further evidence that this entity is a peripheral nerve sheath tumor and is unrelated to melanocytic neoplasms.

Neural spectrum: palisaded encapsulated neuroma and verocay body poor dermal schwannoma

We examined 25 palisaded encapsulated neuromas (PEN) of the skin and used peripherin antibody as an immunohistochemical label for axons. Quantitative analysis of the axon to schwann cell nuclear ratio for each PEN was determined by examining cross-sectioned neuroid fascicles. This revealed that 120 of the 253 cross-sectioned fascicles in PEN lacked axon and only 5% of the fascicles had an axon to schwann cell nuclear ratio greater than 1:2. In contrast, all fascicles in 40 dermal nerves adjacent to PENs as well as 35 traumatic neuromas in surgical scars had an axon to schwann cell nuclear ratio of at least 1:2 and the majority a ratio of 1:1 or higher. These results suggest that there is a spectrum between PENs which are axon rich to a form of schwannoma with an identical histopathology which lacks significant axonal content and that not all PENs are true neuromas.

Cutaneous nerve hypertrophy

We present a case of cutaneous nerve hypertrophy possibly secondary to scratching or other trauma. The patient was symptomatic and sought surgical treatment, despite no clinical lesion being evident. This type of change has not been previously reported in this clinical setting. There was no clinical evidence of multiple endocrine neoplasia-type 2b (MEN-2b). Awareness of this entity may avoid unnecessary surgery.

Benign neural tumors of the oral cavity: a comparative immunohistochemical study

To determine if immunohistochemistry can be used as adjunct to the diagnosis and classification of oral benign neural tumors, we stained 77 neurally differentiated tumors with a panel of neural-associated antibodies (S-100 protein, CD57, epithelial membrane antigen, factor XIIIa, CD34, CD68, collagen IV). Using standard histologic criteria, we identified 13 schwannomas, 16 neurofibromas, 23 traumatic neuromas, 16 palisaded and encapsulated neuromas, and 9 granular cell tumors from archived oral pathology specimens. Silver stains showed that neurofibromas, traumatic neuromas, and palisaded and encapsulated neuromas consistently contained axon filaments. Although all neural tumors contained S-100-positive cells, schwannomas and palisaded and encapsulated neuromas contained the most. All tumors expressed CD57; traumatic neuromas were stained intensely and the others stained weakly. The consistent epithelial membrane antigen capsular staining of schwannomas and the absence of factor XIIIa-positive dendritic/spindle cells helped distinguish these tumors from others. Many CD34-positive cells were found in schwannomas, and few were found in palisaded and encapsulated neuromas. Variable numbers CD68-positive cells were seen in all neural tumor types; some of these cells appeared to be macrophages and mast cells, but many were thought to be Schwann cells expressing this antigen. Collagen IV staining, apparently representing basement membrane, was generally a feature of all benign neural tumors. The immunophenotype of the granular cells of the GCTs was S-100+, CD57+, and collagen IV+ supporting the putative neural origin of these tumors. We conclude that neural origin/differentiation of a connective tissue tumor can be confirmed with stains for S-100 protein, epithelial membrane antigen, CD57, and collagen IV. Staining patterns and intensities associated with the panel of antibodies tested can be useful in tumor classification.

Idiopathic solitary neuroma of skin with unusual histologic changes

We report herein a case of idiopathic solitary neuroma with vascular proliferation and neurofibroma-like features. Clinically, the skin lesion was a 0.7 cm nodule without tenderness on the forearm. Histologically, there was vascular proliferation in the upper dermis, some neural structures among the proliferative vasculature in the mid dermis and large bundles of neural structures extending in various directions in the mid and deep dermis (resembling neurofibroma). Special stains, such as Masson's trichrome and Luxol fast blue, and immunohistochemical studies, including S-100 protein, neuron-specific enolase (NSE), vimentin, desmin, factor-VIII related antigen and epithelial membrane antigen (EMA), were added for this very rare case.

Cutaneous plexiform schwannoma associated with neurofibromatosis type 2

BACKGROUND

Plexiform schwannoma (PS) is a rare benign tumor of the nerve sheath that can be located either in the deep soft tissues or in the dermis or subcutis. The tumor predominantly affects young adults and occurs most commonly as a slowly growing asymptomatic solitary nodule in the head and neck region, trunk, and upper extremities.

METHODS

A cutaneous PS located in the preauricular region of a 19-year-old white female is reported. The patient exhibited six "café-au-lait" spots in the trunk and the extremities. Magnetic resonance imaging examination showed bilateral tumors in both acoustic nerves (considered schwannomas) and also masses in the right major sphenoidal wing, falx, and T2-T3 level of rachis and a solid and cystic tumor in the low medulla oblongata. Tumors of the preauricular region, medulla oblongata, spinal cord at level T2-T3, and major sphenoidal wing area were surgically removed. The tumors were studied by immunohistochemistry and diagnosed as PS, pilocytic astrocytoma, and meningiomas, respectively.

RESULTS

Seventy-eight cases of PS have been reported in the literature: 8 (10.2%) have been associated with clinical schwannomatosis, 6 (7.7%) with multiple cutaneous schwannomas syndrome, and only 3 (3.8%) with neurofibromatosis type 1 (NF-1).

CONCLUSIONS

In this report, to the authors' knowledge, for the first time PS is described associated with neurofibromatosis type 2. The tumor does not appear to have significant association with NF-1. Plexiform schwannoma should be recognized because it may be misdiagnosed as plexiform neurofibroma or other plexiform malignant tumors. Differentiation from plexiform neurofibroma is important, because the latter is virtually pathognomonic of neurofibromatosis type 1 and has a propensity for malignant transformation.

Multinodular versus plexiform neurilemoma of the hard palate. Report of a case

Neurilemoma (schwannoma) is the most commonly encountered nerve sheath tumor of the oral cavity. It generally appears as a single encapsulated nodule that occasionally causes pain or discomfort. The tongue is involved most frequently, followed by the palate, floor of mouth, and buccal mucosa. Neurilemomas occur most often during the second or third decades of life. Our patient is a 21-year-old woman with a recurrence of a palatal mass that was excised 3 years earlier. Histologically the lesion appeared to be a multinodular neurilemoma, a pattern rarely reported in the oral cavity.