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We present six cases of a plexiform nerve sheath tumor of childhood that previously had been designated a form of malignant peripheral nerve sheath tumor (MPNST), and we provide evidence that such tumors are in fact benign plexiform cellular schwannomas. At presentation, the four girls and two boys ranged in age from 2 to 15 months with tumors of the leg (four), deep groin and upper thigh (one), and pelvis (one). Of the six lesions, five were congenital and none was associated with type 1 neurofibromatosis. Tumor sizes ranged from 2.0 to 9 cm, with three larger than 5 cm. Three tumors were well circumscribed, two were purely infiltrative, and one had a mixed circumscribed and infiltrative growth pattern. Peripheral nerve involvement was evident in two cases. Grossly, the tumors were multinodular or plexiform in configuration and, on sectioning, lobulated and homogeneously tan without necrosis. Characteristic histologic features included hypercellularity, composition of cells spindle in shape with elongate hyperchromatic nuclei, and indistinct cellular outlines. Their nuclei varied minimally in size and shape but were at least three times the size of typical neurofibroma nuclei. Mitoses were seen in every tumor and in the areas of greatest proliferative activity ranged from 4 to 31/10 high power fields. MIB-1 staining of at least 30% of the cells was noted in three cases. In five cases in which p53 immunoreactions were performed, no nuclear staining was evident. That the tumors are schwannomas was evident from their uniform strong staining for S-100 protein and an ultrastructure in all five cases showing only differentiated neoplastic Schwann cells. Architecturally, the tumors differed from conventional schwannoma and nonplexiform cellular schwannomas by their lack of both well-formed capsules and degenerative changes. Follow-up was available in all cases and ranged from 2 to 13.6 years. All tumors recurred locally and were treated by local resections. With the exception of one child lost to follow-up at 25 months, all the children are alive and free of disease. Our data combined with cases previously reported by Meis-Kindblom and Enzinger show a childhood peripheral nerve tumor unassociated with type 1 neurofibromatosis, occurring most commonly in infants, often presenting as a congenital tumor and, though prone to local recurrence, having no metastatic potential. The behavior is that of a benign tumor, although its often rapid growth, hypercellularity and increased mitotic activity, sometimes locally aggressive behavior, and difficulties encountered in obtaining tumor-free margins are unsettling to pathologist and clinician alike. These features may lead to a misdiagnosis of malignancy, which could result in harmful overtreatment.

ejd.2011.1609 Auteur(s) : Jiong Zhou, Xiao-Yong Man, Min Zheng, Sui-Qing Cai cai.suiqing@gmail.com Department of Dermatology, Second Affiliated Hospital, Hangzhou 310009, China Schwannomas are benign neurogenic tumors, first described by Verocay in 1908 [1]. There are 7 subtypes: classical (Verocay), cranial nerve, cellular, plexiform, degenerated (ancient), melanotic, and granular cell schwannoma [2]. Plexiform schwannoma is a rare subtype, accounting for approximately 5% of schwannomas [2]. Sometimes, [...]

We report a patient with a plexiform schwannoma located in the cervical part of the esophagus. A large pedunculated intraluminal polyp, originating in the postcricoid region and protruding into the oropharynx, was found in association with multiple submucosal nodules. Both the intraluminal polyp and submucosal nodules consisted of cellular schwannomatous tissue. The patient showed no signs of neurofibromatosis or schwannomatosis. Plexiform schwannomas are uncommon tumors, mainly confined to the dermis and subcutis of trunk, head, and neck region and upper extremities. Visceral examples are vanishingly rare, and a location in the esophagus has not yet been described. The intruiging mode of presentation in the present case, mimicking that of so-called giant esophageal fibrovascular polyp, probably relates to mechanical factors inherent to the unique esophageal location, Int J Surg Pathol 8(4):353-357, 2000

We present a case of subcutaneous plexiform schwannoma, a rare benign peripheral nerve sheath tumour characterized by a multinodular and plexiform growth pattern. A review of the literature was performed to identify the relationship between plexiform schwannoma and neurofibromatosis types 1 and 2, and schwannomatosis.It is also important to distinguish plexiform schwannoma from plexiform neurofibroma, a particular type 1 neurofibromatosis lesion, because of the propensity of the latter for malignant degeneration.

The present report describes a plexiform schwannoma involving the subcutis of the foot in an 8-year-old boy. Gross findings revealed thin fibrous septa in a multilobulated tumor that was partly separated into free body-like nodules in the subcutis. Preoperative CT and MRI failed to delineate this multinodular architecture or free bodies. This is a case presentation including the CT and MR findings associated with plexiform schwannoma.

We describe a 42-year-old man who had tumors occupying the right deep neck through the upper part of the mediastinum. The right vocal cord was fixed and bulgings of the pharyngeal and tracheal wall were observed. At surgery, the masses were subtotally removed as much as possible. Histological examination revealed that they were schwannomas. The postoperative course was uneventful, except for the presence of hoarseness.

Cutaneous plexiform schwannoma is a rare multilobulated variant of benign schwannoma. When presenting as the cellular subtype with significantly increased proliferative rate, diagnostic consideration of a malignant peripheral nerve sheath tumor is prompted. However, follow up demonstrates a benign natural history with propensity for local recurrence and typical lack of association with neurocutaneous syndromes. These lesions most commonly occur as cutaneous and subcutaneous masses of the extremities in the first four decades. Only 9 cases of congenital tumors are reported. A case of congenital plexiform cellular schwannoma, presenting as a cutaneous mass measuring 3.5 × 2.5 × 2.0 cm, excised from the left upper arm of a 16 month old female is discussed. Regions of increased cellularity and proliferation co-localized and were unassociated with nuclear anaplasia. Mitotic figures numbered 7 per 10 400x fields. The tumor cells were strongly immunoreactive for S-100 protein. The MIB-1index was multifocally 25% and p53 protein over expression was present in 50% of nuclei. Following excision with free margins the tumor locally recurred after 16 months. The recurrence was morphologically identical to the original lesion. Recognition of the clinical and morphological characteristics of this rarely encountered benign neoplasm will facilitate in diagnosing this entity.

Only three cases of clitoral schwannoma have been reported in the English language literature, with none of them being a plexiform schwannoma. Here we report the first plexiform schwannoma of the clitoris. A 41-year-old woman without neurofibromatosis presented with a 2 x 2 cm, slowly growing, painless tumor of the clitoris. Simple excision of the tumor was performed, and pathological examination revealed a plexiform schwannoma. No evidence of recurrence was noted after 2 years of follow-up. Despite its rarity, a schwannoma should be included in the differential diagnosis of a clitoral enlargement or mass. Our case, despite its unique plexiform growth pattern, has clinical features similar to those of other reported cases of clitoral schwannoma.

A 5-year-old girl presented with a 3 year history of a slow-growing lump in the right labia minora. On examination, a 20×15 mm mass was attached to the overlying vulva skin. After an initial incomplete resection the lump recurred twice, with subsequent repeat excisions 10 and 12 years after initial presentation. Microscopic examination of all three excisional biopsies revealed classical histological features of plexiform schwannoma, namely Antoni A and B areas including Verocay bodies and a multinodu-lar architecture. The most recent excision performed in 2012 also contained scattered bizarre pleomorphic nuclei, consistent with ancient change. Diffuse strong positive staining for S100 was seen. Plexiform (multinodular) schwannoma is an uncommon variant of schwannoma, accounting for approximately 5%. This variant is characterised by a multinodular growth pattern, and can occur in both conventional and cellular types of schwannoma. Plexiform schwannomas can occur in both superficial and deep soft tissues, however the vulva is an uncommon site. Most cases of plexiform schwannoma have no association with neurofibromatosis. Plexiform neurofibroma is an important differential diagnosis to exclude. As seen in our case, plexiform schwan-noma can recur locally, which is thought to be related to the mul-tinodular growth pattern. Malignant transformation and distant metastases of plexiform schwannoma have not been reported.

A plexiform schwannoma is a distinct and rare subtype of a benign solitary schwannoma. This is a description of the tumor associated with macrodactyly.

lateral side which caused penis curvature ( fig. 1 ). Ultrasonographic examination detected a 6.0 ! 5.0 ! 2.0 cm hypoechoic mass with irregular margins. A pelvic CT scan showed that the tissue was located beside the left corpus spongiosum with soft tissue density ( fig. 2 ). The postoperative pathological diagnosis was benign plexiform schwannoma. Dear Sir, Schwannomas usually occur along the peripheral nerves but are very rare at the penis [1, 2] . A 35-year-old man presented to our clinic seeking evaluation for a painless swelling on his penis. He had first noticed the mass 5 years before presentation; it gradually increased in size and recently interfered with sexual activity. Examination revealed a cordlike mass on the left Received: July 10, 2012 Accepted: July 29, 2012 Published online: November 27, 2012

Plexiform schwannoma is a benign neoplasm of the peripheral nerves. It is generally localized in the skin and subcutaneous tissues of the head, neck, arms, and chest. Visceral localization of plexiform schwannoma is very uncommon (1). In particular, gastric involvement of plexiform schwannoma is extremely rare. Neurofibromatosis type 2 (NF2) is a dominantly inherited tumor-prone disorder characterized by the development of multiple schwannoma and meningiomas (2). The clinical features of NF2 typically include nervous system tumors and ocular abnormalities (3). We present a case in an 18-year-old man affected by NF2 with a gastric plexiform schwannoma, which was confirmed by endoscopic biopsy. To our knowledge, the case we present is the first report of a patient affected by NF2 with extremely rare case of gastric schwannoma. CASE REPORT

Summary An immunohistochemical study using a comprehensive panel of antibodies to Schwann cell markers, intermediate filaments and extracellular matrix components has been performed on three cases of plexiform schwannoma. All tumour cells expressed S 100 protein, Leu 7-HNK 1 antigen and vimentin; glial fibrillary acidic protein was detected in many tumour cells. In addition, expression of cytokeratin was also demonstrated in one case. The associated extracellular matrix was found to be reactive with antibodies to laminin, heparan sulfate proteoglycan, fibronectin, type I, III, IV and VI collagen. It is concluded that Schwann cells producing their own extracellular matrix are the main components of these tumours. The significance of the cytokeratin expression and the possible role of the extracellular matrix in regulating Schwann cells' proliferation in peripheral nerve tumours are discussed.

To the Editor.— Schwannomas (neurilemomas) are rare benign nerve tumors, usually presenting as solitary encapsulated subcutaneous nodules adherent to a peripheral nerve. It is most uncommon for schwannomas to possess multinodular intertwining characteristics (ie, a plexiform pattern). Plexiform schwannomas (PS) have often been confused with plexiform neurofibromas. 1 Unlike the latter, which have a strong association with neurofibromatosis (NF), PS seem to affect exclusively the skin as solitary or multiple lesions. 2,3 Nonetheless, there seems to be a small but definite association between PS and NF, 2 and, recently, multiple cutaneous plexiform schwannomas (MCPS) have been reported in Japan as a marker of a novel neurocutaneous syndrome, neurilemomatosis (NL). 4 We report a case of MCPS with multiple tumors of the central nervous system in the absence of any cutaneous and genetic marker for NF. Report of a Case.— An 18-year-old normally intelligent woman was born to a family without

R E F E R E N C E S 1. Shishiba T, Nimura M, Ohtsuka F, et al. Multiple cutaneous neurilemmomas as a skin manifestation of neurilemommomatosis. J Am Acad Dermatol 1984;10:744-54. 2. Vai-Bernal F, Figols J, Vasquez-Barquero A. Cutaneous plexiform schwannoma associated with NF type 2. Cancer 1995; 76:1181-6. 3. Reith JD, Goldblum JR. Multiple cutaneous schwannomas: report of a case and review of the literature with reference to the association with types 1 and 2 neurofibromatosis and schwannomatosis. Arch Pathol Lab Med 1996;120:399-401. 4. Nimura M. Aspects of neurofibromatosis from the viewpoint of dermatology. J Dermatol 1992;19:868-72. 5. Enzinger FM, Zhang R. Plexiform fibrohistiocytic tumor presenting in children and young adults: an analysis of 65 cases. Am J Surg Pathol 12:818-26. 6. Meis-Kindblom JM, Enzinger FM. Plexiform malignant peripheral nerve sheath tumor of infancy and childhood. Am J Surg Pathol 1994;18:479-85. 7. Woodruff JM, Scheithauer BW. Nerve sheath tumors. Am J Surg Pathol 1995;19:608-9.

Four cases of neurilemmomatosis with multiple cutaneous neurilemmomas are described, including clinical, histologic, and electron microscopic features. Thirteen definite cases and sixteen probable cases of neurilemmomatosis with cutaneous tumors were collected from the Japanese literature. The skin lesions of multiple cutaneous neurilemmomas are nodules, infiltrated pigmented lesions, and plaque-like lesions consisting of papules. From the findings presented here, neurilemmomatosis is a clinical entity clearly distinguished from the neurofibromatosis of von Recklinghausen's disease.

We describe a rare variant of schwannoma characterized by a interconnecting multinodular growth mimicking a plexiform neurofibroma. The schwannoma recurred twice. The second recurrence was not excised and has not increased in size for 1 1/2 years. The patient is alive and well, 3 years and 4 months after the first excision with no clinical evidence of metastasis.

Plexiform schwannoma is an infrequent variant of schwannoma characterized grossly and microscopically by multi-nodular growth. Although plexiform schwannoma has such growth patterns, it is a benign tumor as well as a conventional schwannoma. It rarely infiltrates adjacent organs or arises from the organ itself. In this report, we describe a case in which plexiform schwannoma involved the tracheal wall and left recurrent laryngeal nerve to a great extent. As it was expected to be difficult to achieve complete resection even if the longer tracheal resection were performed, we preserved the trachea and resected as much of the tumor as possible. This report is thought to be the first to describe plexiform schwannoma infiltrating or growing from the trachea. Although the treatment decisions we made might be controversial, we believed we could make an accurate diagnosis and adequate treatment decision through surgery. Electronic supplementary material The online version of this article (doi:10.1186/s40792-015-0070-0) contains supplementary material, which is available to authorized users.

Background It is often challenging to completely resect multinodular/plexiform schwannomas involving important deep nerves using minimally invasive surgically techniques. Case description A 32-year-old woman presented with a 5-year history of a slowly growing, painful mass in the medial aspect of the right ankle. Magnetic resonance imaging (MRI) demonstrated multiple nodular lesions with iso-signal intensity relative to skeletal muscle on T1-weighted sequences and heterogeneous high signal intensity on T2-weighted sequences. Mild to moderate enhancement was identified after gadolinium administration. All 58 tumors were completely enucleated using an intracapsular technique. Histological examination confirmed the diagnosis of schwannoma consisting mainly of Antoni A areas. The burning sensation was relieved immediately after surgery. The patient had no aggravated neurological deficit and was very satisfied with the outcome of the treatment at final follow-up. Discussion and evaluation We experienced a very rare case of a large multinodular/plexiform schwannoma arising from the posterior tibial nerve and its larger terminal branch. Our case had the characteristic MRI features of this condition. It is extremely important to differentiate multinodular/plexiform schwannoma from plexiform neurofibroma and malignant peripheral nerve sheath tumor, with complete surgical enucleation being curative. Conclusions MRI is a clinically useful modality in the evaluation and detection of deep-seated multinodular/plexiform schwannoma. Intracapsular enucleation seems to be an acceptable treatment for this peculiar tumor located in the foot and ankle.

Background Schwannomas are slow-growing typically encapsulated tumors composed of differentiated Schwann cells, the primary class of peripheral glial cells. Complete excision is the treatment of choice for orbital schwannomas that cause pain, disfigurement, diplopia, or optic neuropathy. The presence of multiple schwannomas in a single patient suggests possible association with neurofibromatosis type 2 (NF2) or schwannomatosis. Case presentation We present 2 patients who experienced recurrent orbital schwannoma without evidence for neurofibromatosis. The recurrence in one patient, a 59-year old man, occurred 6 years after complete excision of the initial tumor. This recurrence consisted of 2 independent tumors in the same orbit. The recurrence in the second patient, a 5 year-old girl, occurred multiple times within days to weeks of partial excisions until eventually a complete excision was performed. Conclusion The clinical history, histopathologic features and particularly the intraoperative findings suggest that the 59 year old man suffers from orbital schwannomatosis, while the rapid recurrence in the second patient correlated with the cellular features of her plexiform schwannoma. Hence, the recurrence in each patient is linked to a different etiology, with implications for treatment and patient counseling given the difficulty in treating orbital schwannomatosis. To our knowledge, this is the first description of isolated orbital schwannomatosis.

Introduction Plexiform schwannoma is one of the least common variants of schwannoma. It is usually found on the trunk, head, neck and upper extremities. Most reported cases are small tumors, less than 2cm in maximum diameter, arising from superficial nerves. Trauma and neurofibromatosis type 2 are well-recognized risk factors for plexiform schwannoma. It is important to differentiate it from plexiform neurofibroma, because the former has neither an association with von Recklinghausen’s disease nor a malignant potential. Case presentation We report a case of a large plexiform schwannoma arising from the posterior tibial nerve in proximity with the medial malleolus. The patient had no history of ankle strain, fracture or neurofibromatosis type 2. Magnetic resonance imaging demonstrated a multinodular, inhomogeneous lesion, measuring 6 × 4 × 2.8 cm. Fine needle biopsy was suggestive of a benign lesion, deriving from neural elements. The mass was excised marginally. Permanent section showed that the lesion was multilobular, surrounded by a thin fibrous capsule and consisting of elongated cells, rare typical mitosis, cells with degenerative features and stained positive for S-100 protein. The patient was not evident disease at the latest follow-up 2.3 years later, with an excellent functional result. No sensory or motor deficits were encountered. Conclusion There are no reports in the literature for large plexiform schwannomas arising from the tibial nerve. Marginal excision seems to be the recommended therapy for this rare tumor.