[Gastric gastrointestinal stromal tumour and schwannoma: An unusual presentation in a patient without neurofibromatosis]

The majority of gastric neoplasms are of epithelial type. Stromal tumours are the next most frequent and are most commonly gastrointestinal stromal tumours, followed by leiomyoma and schwannoma. We present an exceptional case of a patient with a gastrointestinal stromal tumour with suspicion of residual gastric disease, which was diagnosed post-operatively as a schwannoma.

Retroperitoneal Schwannomas: Diagnostic and Therapeutic Implications

Aims and background

Schwannomas are a rare group of soft-tissue tumors that are derived from the peripheral nerve sheath and rarely develop in the retroperitoneum.

Methods and study design

We reviewed the clinicopathological features of 4 patients referred to our unit between October 1999 and March 2004 who on radiological examination were diagnosed with pancreatic, adrenal, psoas and retroperitoneal fat tissue tumors and subsequently underwent surgical treatment.

Results

The preoperative diagnosis was incorrect in all cases. At time of surgery, we found a mass probably arising from the adrenal gland in 2 patients, a lesion originating from the femoral nerve in 1 patient, and a retroperitoneal mass without a clear site of origin in 1 patient. Pathological evaluation revealed schwannomas in all cases, with no signs of malignancy. Complete surgical excision was performed in all patients without any major postoperative complications. At the time of writing all patients are alive with no evidence of local or distant recurrence.

Conclusions

Radical surgical excision is considered the best treatment for these neoplasms, resulting in a very good long-term prognosis.

Successful treatment of a giant ossified benign mesenteric schwannoma

Primary benign schwannoma of the mesentery is extremely rare. To date, only 9 cases have been reported in the English literature, while mesenteric schwannoma with ossified degeneration has not been reported thus far. In the present study, we present the first giant ossified benign mesenteric schwannoma in a 58-year-old female. Ultrasound, computed tomography and magnetic resonance imaging were used, but it was still difficult to determine the definitive location and diagnose the mass. By laparotomy, a 10.0 cm × 9.0 cm × 9.0 cm giant mass was found in the mesentery and was then completely resected. Microscopically, the tumour located in the mesentery mainly consisted of spindle-shaped cells with a palisading arrangement. Some areas of the tumour were ossified, and a true metaplastic bone formation was observed, with the presence of bone lamellae and osteoblasts. Immunohistochemical investigation of the tumour located in the mesentery showed that the staining for the S-100 protein was strongly positive, while the stainings of SMA, CD34, CD117 and DOG-1 were negative. The cell proliferation index, measured with Ki67 staining, was less than 3%. Finally, a giant ossified benign mesenteric schwannoma was diagnosed. After surgery, the patient was followed up for a period of 43 mo, during which she remained well, with no evidence of tumour recurrence.

Colonic Schwannoma: A Case Study and Literature Review of a Rare Entity and Diagnostic Dilemma

An asymptomatic 73-year-old woman was found to have a submucosal mass in the descending colon on routine colonoscopy. A CT scan revealed a 31 × 28 × 31 mm lesion in the same location. Previous biopsy proved to be nondiagnostic, and the patient underwent a laparoscopic descending colon resection. Histologic evaluation of the tumor revealed a low grade spindle cell neoplasm with strong, diffuse positivity for S-100 protein by immunohistochemistry, leading to the diagnosis of schwannoma. A review of the literature revealed intestinal schwannoma to be a rare disease entity, with only about 50 cases previously reported.

Melanotic schwannoma of thoracic spinal root mimics metastatic melanoma: a potential pitfall for misdiagnosis

Melanotic Schwannoma (MS) is a kind of rare subtypes of Schwannoma. In this tumor, amounts of melanin always mislead inexperienced pathologists to a diagnosis of primary or metastastic melanoma. Different from the ordinary Schwannoma, MS is considered as a low malignant nerve sheave tumor. Here we present a case of MS arising from the thoracic spinal and initially was misdiagnosed as metastastic melanoma. But the patient followed a benign course, without recurrent in 30 months follow-up.

Primary adrenal microcystic/reticular schwannoma: clinicopathological and immunohistochemical studies of an extremely rare case

A case of primary adrenal microcystic/reticular schwannoma affecting the right adrenal gland in a 31-year-old female was reported. Histologically, the tumor significantly consisted of strikingly anastomosing strands of spindle cells imparting a microcystic and reticular pattern with a focal transition to epithelioid nests. Immunohistochemically, S-100 and CD56 protein showed a uniform and strong positivity, GFAP and EMA weakly and focally expressed, but AE1/AE3, CK5/6, CD31, CD34, calrentin, D2-40, WT1, CgA, Melan-A and Neu-N were negative. The patient live through a calm period for 4 months after the whole right paranephros was removed with no evidence of relapse. This interesting case showed primary adrenal microcystic/reticular schwannoma is characteristic of a distinctive and infrequent morphology compared to another subtype of schwannoma involved in the paranephros. To be familiar with its significant histological features would prompt us to take it into consideration when facing the mimickers.

A neurogenic tumor containing a low-grade malignant peripheral nerve sheath tumor (MPNST) component with loss of p16 expression and homozygous deletion of CDKN2A/p16: a case report showing progression from a neurofibroma to a high-grade MPNST

Development of malignant peripheral nerve sheath tumors (MPNSTs) is a stepwise process that involves the alteration of many cell cycle regulators and the double inactivation of the NF1 gene. Inactivation of the TP53 gene and deletion of the CDKN2A/p16 gene are known to play an important role in the process. Herein, we present a 19-year-old man with a familial history of neurofibromatosis type 1, in whom the tumor arose from the intercostal nerve and showed 3 components: a neurofibroma, a low-grade MPNST, and a high-grade MPNST. Loss of p16 expression and homozygous deletion of the CDKN2A/p16 gene were observed in both the low-grade and the high-grade MPNST. In contrast to low-grade MPNSTs, high-grade MPNSTs generally tend to lose expression of p16 and harbor homozygous deletion of the CDKN2A/p16 gene. Loss of p16 expression and homozygous deletion of the CDKN2A/p16 gene in low-grade MPNST in our case might be related to its progression to high-grade MPNST. To the best of our knowledge, this is the first study correlating the p16 expression status and CDKN2A/p16 gene alteration in low-grade MPNSTs.

Gastroduodenal intussusception due to gastric schwannoma treated by billroth II distal gastrectomy: One case report

Schwannomas are rarely observed in the gastrointestinal tract. The most common symptoms of a gastric schwannoma are abdominal pain or dyspepsia, gastrointestinal bleeding, and an abdominal mass. Many gastric schwannomas are asymptomatic and are discovered incidentally or at postmortem. The diagnosis of a schwannoma is based on immunohistochemical positivity for S-100 protein. We present a case report of a rare complication of gastric schwannoma causing gastroduodenal intussusception that was successfully managed by a Billroth II distal gastrectomy. In this rare case, the patient had intermittent, colicky abdominal pain, nausea, and vomiting for over 4 wk accompanied by a weight loss. A diagnosis of gastric intussusception was made by computed tomography. A Billroth II distal gastrectomy was then performed, and complete en bloc removal (R0 resection) was achieved. Pathology confirmed a gastric schwannoma through positive immunohistochemical staining for S-100 protein.

Endoscopic full-thickness resection and laparoscopic surgery for treatment of gastric stromal tumors

AIM: To assess the effectiveness of endoscopic full-thickness resection (EFR) and laparoscopic surgery in the treatment of gastric stromal tumors arising from the muscularis propria.

METHODS: Out of 62 gastric stromal tumors arising from the muscularis propria, each > 1.5 cm in diameter, 32 were removed by EFR, and 30 were removed by laparoscopic surgery. The tumor expression of CD34, CD117, Dog-1, S-100, and SMA was assessed immunohistochemically. The operative time, complete resection rate, length of hospital stay, incidence of complications, and recurrence rate were compared between the two groups. Continuous data were compared using independent samples t-tests, and categorical data were compared using χ² tests.

RESULTS: The 32 gastric stromal tumors treated by EFR and the 30 treated by laparoscopic surgery showed similar operative time [20-155 min (mean, 78.5 ± 30.1 min) vs 50-120 min (mean, 80.9 ± 46.7 min), P > 0.05], complete resection rate (100% vs 93.3%, P > 0.05), and length of hospital stay [4-10 d (mean, 5.9 ± 1.4 d) vs 4-19 d (mean, 8.9 ± 3.2 d), P >0.05]. None of the patients treated by EFR experienced complications, whereas two patients treated by laparoscopy required a conversion to laparotomy, and one patient had postoperative gastroparesis. No recurrences were observed in either group. Immunohistochemical staining showed that of the 62 gastric stromal tumors diagnosed by gastroscopy and endoscopic ultrasound, six were leiomyomas (SMA-positive), one was a schwannoglioma (S-100 positive), and the remaining 55 were stromal tumors.

CONCLUSION: Some gastric stromal tumors arising from the muscularis propria can be completely removed by EFR. EFR could likely replace surgical or laparoscopic procedures for the removal of gastric stromal tumors.

Bowel mesentery (meso-appendix) microcystic/reticular schwannoma: Case report and literature review

Microcystic/reticular schwannoma is a recently described variant of schwannoma with a predilection for the gastrointestinal tract. Due to overlapping features with other tumors, unawareness of this tumor type may lead to diagnostic and therapeutic pitfalls. We here report a case of microcystic/reticular schwannoma arising in the meso-appendix of a 43-year-old woman. The tumor was incidentally discovered by computed tomography scan for unrelated reasons. A laparoscopic operation was performed shortly after admission. Histological examination revealed a circumscribed tumor with a striking microcystic and cribriform architecture. Immunohistochemically, the tumor cells were diffusely positive for S100 protein, glial fibrillary acid protein and protein gene product 9.5, which were consistent with a peripheral nerve sheath tumor. The patient remains well with no signs of recurrence at a 10-mo follow-up. To our knowledge, this is the first case of microcystic/reticular schwannoma arising in the meso-appendix. Albeit very rare, microcystic/reticular schwannoma should be included in the differential diagnosis of appendiceal tumors.

Cystic schwannoma of eyelid in an Indian male: a rare presentation

Eyelid schwannoma (neurilemmomas) is an extremely rare, benign neoplasm. A case of Cystic Schwannoma in eyelid of a young adult is reported. A 19-year-old male presented with a firm-nodular painless lesion, 3.5 cms in diameter, located on the left lower eyelid for the last 2 years. The lesion was surgically excised. Histopathological diagnosis of cystic schwannoma was made. Immunohistochemistry revealed strong S-100 positivity indicative of Schwann cell origin. No recurrance was seen after a follow up of 1 year.

The controversial nosology of benign nerve sheath tumors: neurofilament protein staining demonstrates intratumoral axons in many sporadic schwannomas

Schwannomas are benign peripheral nerve sheath tumors believed to be composed purely of cells with ultrastructural features of Schwann cells; these tumors are believed to develop eccentrically from the surface of nerves and not to contain axons, other than immediately beneath the capsule. This concept has recently been disputed in cases associated with neurofibromatosis type 2. The usual presence of intratumoral axons in neurofibromas is said to allow easy distinction from schwannomas. Eighty sporadic schwannomas (20 conventional, 20 cellular, 20 ancient, 10 gastric, and 10 plexiform) were retrieved from the authors' files. Hematoxylin-and-eosin stained slides were reviewed, diagnoses were confirmed and all tumors were stained for S-100 protein and neurofilament protein (NFP). The amount (rare, focal, multifocal, and diffuse) and distribution (central and/or peripheral) of axons within the tumors were analyzed. All tumors were strongly and diffusely positive for S-100 protein (nuclear and cytoplasmic staining). NFP-positive axons were identified in 11 of 20 (55%) conventional schwannomas (2 rare, 4 focal, 3 multifocal, and 2 diffuse; 5 central, 4 peripheral, and 2 central and peripheral) and in 15 of 20 (75%) cellular schwannomas (3 rare, 6 focal, and 6 multifocal; 12 central, 1 peripheral, and 2 central and peripheral). Of the 20 ancient schwannomas, 7 cases (35%) showed intratumoral axons, highlighted by NFP immunostaining (1 rare, 4 focal, 1 multifocal, and 1 diffuse; 4 peripheral, 2 central, and 1 central and peripheral). Most cases of gastric schwannoma showed no evidence of intratumoral axons; 9 cases (90%) were negative for NFP and only 1 case (10%) was positive (focal and central). Seven of 10 cases (70%) of plexiform schwannomas were negative for NFP, whereas only 3 cases (30%) showed positive axons (2 multifocal and 1 focal; 3 central). The unexpected but quite frequent presence of intratumoral axons in schwannomas argues against conventional views of these lesions' pathogenesis as an eccentric encapsulated lesion and raises the possibility that a more diverse cell population, perhaps more closely resembling neurofibromas, may constitute these neoplasms. Although NFP-positive axons were most often present in the conventional and cellular variants of schwannoma, their presence was also observed in a minority of ancient, gastric and plexiform schwannomas. Differentiation between neurofibroma and schwannoma in cases with overlapping cytoarchitectural features should not be based solely on the presence or absence of NFP-positive axons within a given tumor.

Expression of Angiopoietin-1, 2 and 4 and Tie-1 and 2 in gastrointestinal stromal tumor, leiomyoma and schwannoma

AIM: To investigate the role of angiopoietin (Ang) -1, -2 and -4 and its receptors, Tie-1 and -2, in the growth and differentiation of gastrointestinal stromal tumors (GISTs).

METHODS: Thirty GISTs, seventeen leiomyomas and six schwannomas were examined by immunohistochemistry in this study.

RESULTS: Ang-1, -2 and -4 proteins were expressed in the cytoplasm of tumor cells, and Tie-1 and -2 were expressed both in the cytoplasm and on the membrane of all tumors. Immunohistochemical staining revealed that 66.7% of GISTs (20 of 30), 76.5% of leiomyomas (13 of 17) and 83.3% of schwannomas (5 of 6) were positive for Ang-1. 83.3% of GISTs (25 of 30), 82.4% of leiomyomas (14 of 17) and 100% of schwannomas (6 of 6) were positive for Ang-2. 36.7% of GISTs (11 of 30), 58.8% of leiomyomas (10 of 17) and 83.3% of schwannomas (5 of 6) were positive for Ang-4. 60.0% of GISTs (18 of 30), 82.4% of leiomyomas and 100% of schwannomas (6 of 6) were positive for Tie-1. 10.0% of GISTs (3 of 30), 94.1% of leiomyomas (16 of 17) and 33.3% of schwannomas (2 of 6) were positive for Tie-2. Tie-2 expression was statistically different between GISTs and leiomyomas (P < 0.001). However, there was no correlation between expression of angiopoietin pathway components and clinical risk categories.

CONCLUSION: Our results suggest that the angiopoietin pathway plays an important role in the differentiation of GISTs, leiomyomas and schwannomas.

Psammomatous melanotic schwannoma presenting as colonic polyps

Psammomatous melanotic schwannoma is an uncommon neoplasm that usually occurs in the setting of Carney's complex. They can occur in the gastrointestinal tract with preferential location in the stomach. A 43-year-old female presented with two colonic polyps at routine endoscopy. The patient was asymptomatic and did not have features of Carney's complex. Both polyps were composed of melanin-containing epithelioid and spindle cells with several psammoma bodies. There was no evidence of cytological atypia or necrosis. The tumor was diffusely positive for S-100, and focally for HMB-45 and melan-A. The differential diagnosis includes melanoma, GIST, pigmented neuroendocrine tumor, and epithelioid leiomyoma. The lack of malignant features separates this lesion from melanoma while the immunophenotype of the other lesions is characteristic.

Esophageal schwannoma: report of a case

We report a case of esophageal schwannoma in a 46-year-old woman who presented with rapidly progressive dyspnea and dysphagia. Chest computed tomography showed a large mediastinal mass, which was extrinsically compressing the trachea, widely adjacent to the upper thoracic esophagus. We performed an axillary right thoracotomy to enucleate the tumor, which was located in the esophageal muscle layer. A definite diagnosis of esophageal schwannoma was made from the pathologic findings, which included positive immunohistochemical staining for S-100 protein and negative staining for c-kit and CD34.

Schwannoma of the breast: a case report and review of the literature

Schwannoma arising within breast parenchyma is very rare. This report describes such a case in a 58-year-old woman. The tumor, which measured 4.4 x 3.5 x 2.1 cm, was painless, mobile and elastic-soft. Mammography showed a well-circumscribed, oval-shaped nodule without microcalcifications. At ultrasonography it appeared as a hypoechoic solid mass. Fine-needle cytology revealed several clusters of spindle cells indicative of a neoplasm of mesenchymal origin. Histological examination evidenced the characteristic morphological appearance of a schwannoma with Antoni A and Antoni B areas. A review of the 23 proven cases of breast schwannoma is included. The main differential diagnostic findings are also discussed.

Orbital schwannoma: histopathologic correlation with magnetic resonance imaging

CASE REPORT

A 45-year-old man presented with an orbital tumour that on MRI was most consistent with a hemangioma. Histopathologic examination disclosed an orbital schwannoma, with cystic and mucinous degeneration complicating radiologic interpretation.

COMMENTS

An array of ancillary studies including orbital ultrasonography may be useful in substantiating the diagnosis preoperatively.

Benign hybrid perineurioma-schwannoma in the colon. A case report

A 48-year-old man of Haitian descent presented with progressive constipation, hematochezia, and weight loss. Colonoscopy and computed tomography scan revealed an obstructing colonic mass, causing intussusception and pneumatosis of the descending/upper sigmoid colon and necessitating an emergency left hemicolectomy. Gross examination revealed a 4.9-cm obstructing mass in the sigmoid colon extending through the muscularis propria. Histologically, the lesional cells were bland, spindled, with tapered and often wavy nuclei set in a loose fibromyxoid stroma. Focally, the lesional cells displayed whorling or storiform growth pattern mixed with spindle wavy cells. In many areas, the cells had bipolar cytoplasmic processes. Immunohistochemistry revealed patchy positivity for epithelial membrane antigen, CD34, vimentin, diffuse positivity for S-100, and negativity for CD117, cytokeratin (AE1/AE3), ALK1, desmin, smooth muscle actin, neuronal nuclei antigen (NeuN), and neurofilament protein. The morphology and immunohistochemical findings were consistent with hybrid perineurioma-schwannoma. Electron microscopic examination revealed the characteristic features of perineuriomal and schwannomatous differentiation. Based upon the histopathology, immunophenotype, and ultrastructure, this tumor was classified as a benign hybrid perineurioma-schwannoma, a counterpart to the tumor described in the soft tissue. This is the first case report of hybrid perineurioma-schwannoma in the colon.

Bilateral Simultaneous Ancient Schwannomas of the Orbit

An unusual case of purely cystic bilateral ancient schwannomas of the orbit is reported. Complete ophthalmologic examination and CT was performed. Diagnosis was established by excisional biopsy of both tumors, including clinicopathologic study. Histologic examination showed a bilateral purely cystic ancient schwannoma. This case underlines the importance of considering neural tumors, including schwannomas, in the differential diagnosis of both cystic and bilateral orbital tumors. As far as we know, no other case has been previously reported.

Is clear cell sarcoma a malignant form of psammomatous melanotic schwannoma?

✓The authors present a case of clear cell sarcoma (CCS) in which the tumor originated in the S-1 nerve root and had been previously diagnosed as psammomatous melanotic schwannoma (PMS). This is the third case of a spinal nerve root origin for CCS reported in the English-language literature. The similar histogenesis of CCS and malignant melanoma supports the hypothesis that biological agents or immunotherapy are potentially important areas of investigation.

The patient underwent S1–3 laminectomy and gross-total resection of the mass lesion. The border of the resection was extended 1 cm distal to the tumor margin. The postoperative period was uneventful. The new histopathological diagnosis was CCS (malignant melanoma of soft tissue). Despite total resection, the patient returned with disseminated disease at the 18-month follow-up visit. His follow-up magnetic resonance image of the lumbar spine revealed sacral L5–S3 involvement of the vertebral bodies along with disseminated cauda equina seeding.

A CCS originating from peripheral nerves is quite rare. The histopathological and immunohistochemical appearance of CCSs resembles those of PMSs. Surgery should be the first choice of treatment.

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.

Proton magnetic resonance spectroscopy findings of a sacrococcygeal schwannoma

Schwannoma is tumor of peripheral nerves, originating from Schwann cells. It is a rare nerve sheath tumor, which frequently occurs in the intracranial acoustic nerve and spinal nerves. We report on a 28-year-old woman who suffered from a large pelvic mass that was diagnosed to be sacrococcygeal schwannoma. The features of proton magnetic resonance spectroscopy (MRS) study are discussed. The magnetic resonance imaging instrument was a 1.5 T, Gyroscan Intera with a body coil as a radiofrequency transmitter and a signal receiver. T2-weighted images were obtained under the following conditions-turbo spin echo (TSE) T2: turbo spin echo repeat time (TR) = 4500 msec, echo time (TE) = 96 msec. Single voxel MRS was performed by the point-resolved spectroscopy technique with a long TE (136 msec). MRS measurement was performed on two different parts of the tumor. As well as strongly elevated choline and lipid signals, the tumor spectrum showed increased N-acetylaspartate resonances. MRS can be used effectively in the preoperative diagnosis of retroperitoneal and pelvic masses, which demonstrate unusual clinical features.

Of all the nerve! A subcutaneous forelimb mass on a cat

A 16-year-old, male, neutered cat had a 2.5 X 1.5 cm mass on the medial aspect of the right carpus. Cytologic examination of a fine-needle aspirate of the mass indicated a markedly pleomorphic population of plasmacytoid to histiocytic-appearing cells. The cytologic diagnosis was malignant neoplasia of probable mesenchymal or round cell origin. The right forelimb was surgically removed and the scapular, axillary, and prescapular lymph nodes were excised. Malignant fibrous histiocytoma was tentatively diagnosed histologically; however, the tumor cells subsequently were found to be negative for histiocytic (MAC 387, antitrypsin), T-cell (CD3), and B-lymphocyte (immunoglobulin light chains, Ly 5/CD45R) markers, and positive for glial fibrillary acidic protein, vimentin, and S-100. Based on the immunohistochemical results, the diagnosis was modified to malignant peripheral nerve sheath tumor (PNST). Six months after surgery, the cat was reported to be well and had no evidence of metastasis. PNSTs are rare tumors in cats, and are considered as synonymous with schwannomas, neurofibrosarcomas, and hemangiopericytomas. In this cat, the plasmacytoid and pleomorphic appearance of the PNSTcells in cytologic and histologic specimens was unusual, and made it difficult to reach an accurate diagnosis without immunocytochemistry.

Clinicopathological, immunohistochemical, and ultrastructural study of 13 cases of melanotic schwannoma

BACKGROUND

Melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features of schwann cells. The description of the course of the tumors differs somewhat, but it is generally considered as a benign lesion. We investigated the clinicopathologic features, immunophenotypes, and ultrastructural features of 13 patients with nonpsammomatous melanotic schwannoma (NPMS).

METHODS

Tumor specimens of each patient were sectioned and stained with hematoxylin-eosin, Fontana-Masson, Prussian blue, and periodic acid-Schiff (PAS). Immunohistochemical markers such as S-100, Leu-7, HMB-45, Melan-A, CK, EMA, vimentin, GFAP, laminin, collagen IV and MIB-1 were detected with the Envision immunohistochemical staining method. Four of the cases were observed by electron microscopy.

RESULTS

Of the 13 patients, 8 were male and 5 female, aged from 11 to 92 years (mean, 38.6 years). The tumor sites included the spinal nerve root (5 patients), cranial nerve (1), greater omentum (1), subcutaneous tissue (3), mesentery (1), bone (1) and mediastinum (1). Eleven patients were followed up for over 2 years, with a mean of 5.9 years. One patient (9.1%) with a primary tumor in the greater omentum developed another primary tumor of the same type in the subcutaneous tissue of the abdominal wall after the first operation. Local recurrence of the tumor was seen in 2 patients (18.2%). One patient (9.1%) showed the local recurrence and metastasis. Seven patients (63.6%) showed no evidence of the recurrence or metastasis. Grossly, all tumors were well-circumscribed and the gross findings were suggestive of melanin-containing tumors. The tumor was composed of spindled and epithelioid cells with abundant intracytoplasmic melanin pigments. Nuclei were round and contained delicate, evenly distributed chromatins as well as small, distinct nucleoli. In some areas, the nucleoli were large and prominent. Rare mitoses were seen in most lesions except the larger omentum lesion. The pigment was shown to be positive for the Fontana-Masson and negative for Prussian blue and PAS. Immunohistochemical staining for S-100, Leu-7, HMB-45, Melan-A, and vimentin were strongly positive. Linear immunoreactions of both laminin and collagen IV was detected in all patients. Ultrastructurally, numerous elongated tumor-cell processes, duplicated basement membrane and melanosomes were observed in all developmental stages.

CONCLUSIONS

Histologically, melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features of schwann cells. Distinguishing between this tumor and malignant melanoma is of paramount importance in planning of management. Immunohistochemically, combined use of laminin and collagen IV is valuable in distinguishing melanotic schwannoma from malignant melanoma. Wide local resection and additional radiotherapy should be advocated. Further studies including cytogenetic or molecular biology are still required to better delineate melanotic schwannoma from malignant melanoma. Appropriate long-term follow-up is needed for all melanotic schwannomas.

Pseudoglandular Elements in Schwannomas

Context.—Uncommon examples of schwannomas are seen in which a coexisting glandular component is present. The pseudoglandular schwannoma is a relatively recently described variant in which cystic spaces are lined by pseudocolumnar or cuboidal-like neoplastic Schwann cells exhibiting an epithelial-like appearance.

Objectives.—To determine the incidence of pseudoglandular elements in schwannomas, to describe the variable morphology of the schwannomas that may contain pseudoglandular elements, and to discuss the potential mechanisms of development and biological significance of these elements.

Design.—We screened 202 schwannomas from any anatomic site for the presence of pseudoglandular elements and examined these with light microscopy, immunohistochemistry, and electron microscopy.

Results.—Sixteen (7.9%) of the schwannomas contained pseudoglandular elements, which ranged from poorly to well organized in appearance and which were found in schwannomas exhibiting a wide range of morphologic appearances. The Schwann cell nature of the cells composing these elements was apparent both immunohistochemically and ultrastructurally. The frequency of proliferative activity within these elements was no greater than that observed throughout the remainder of the respective schwannomas.

Conclusions.—Our observations suggest that, rather than representing a distinct phenotypic schwannoma variant, pseudoglandular elements likely arise as a response to a degenerative phenomenon, perhaps reflecting the propensity that the Schwann cell has to palisade formation. Such elements may be found within a variety of schwannoma variants and do not appear to possess a unique growth potential.

Hybrid peripheral nerve sheath tumors: Schwannoma-perineurioma and neurofibroma-perineurioma. A report of three cases in extradigital locations

We present three cases of subcutaneous tumors with hybrid features of schwannoma-perineurioma (one case) and neurofibroma-perineurioma (two cases), which occurred in two women aged 50 and 52 years and one man aged 52. Locations included the scapular area, skin overlying breast and knee area. The tumors were 1.5, 4 and 5 cm in largest diameter. None of the patients had signs of neurofibromatosis. All tumors were surgically removed, and patients remained disease-free for 1 to 4 years. The classification of the lesion into schwannoma-perineurioma and neurofibroma-perineurioma rested on histopathological and immunohistochemical findings. An ultrastructural study was performed in one case of neurofibroma-perineurioma. All cases were studied for mutation of the NF2 gene, and in one case (neurofibroma-perineurioma) a point mutation was detected in exon 15 of the gene.

Benign Cutaneous Epithelioid Schwannoma

Benign peripheral nerve sheath tumors are relatively common. They are mostly characterized by the presence of delicate S-shaped spindle cells and myxoid stroma. Although variants with epithelioid foci can be present, the pure epithelioid variant of benign cutaneous schwannoma is extremely rare. It was first reported as cutaneous epithelial schwannoma by Kindblom et al in 1998. Since then, only six cases have been reported. Care should be taken not to misdiagnose them as malignant neoplasms. Their diagnosis can be problematic as their histopathologic features may overlap with those of other soft-tissue and melanocytic tumors. We report a case of cutaneous epithelioid schwannoma and review of the literature.

Immunohistochemical staining for calretinin is useful for differentiating schwannomas from neurofibromas

We studied 25 cases of schwannoma and 42 cases of neurofibroma immunohistochemically with antibodies to calretinin and S-100 protein to explore the potential usefulness of calretinin in differentiating schwannomas from neurofibromas. Of 25 schwannomas, 24 (96%) showed moderate to strong staining for calretinin, with the extent of staining ranging from focal to diffuse. In contrast, only 3 (7%) of 42 neurofibromas displayed focal weak to moderate staining with calretinin. All 42 cases of neurofibromas and all 25 cases of schwannomas showed diffuse moderate to strong staining with S-100 protein. Calretinin also labeled mast cells, whose presence was confirmed further by staining for c-kit, which commonly was present in both tumor types in a scattered individual cell pattern easily differentiated from the clustered pattern of neoplastic spindle cells. Taken together, these results indicate that calretinin is detected in almost all schwannomas and in only a small percentage of neurofibromas, suggesting it is a useful marker for differentiating schwannomas from neurofibromas. Although mast cells present in these 2 neoplasms also react with calretinin, the pattern of staining can be distinguished easily from that of neoplastic cells.

Perineurial cells and nerve axons in gastrointestinal schwannomas: a similarity with neurofibromas. An immunohistochemical study of eight cases

Gastrointestinal schwannoma (GIS) is a distinctive and extremely rare lesion showing some differences from conventional soft tissue schwannoma and some similarities with common soft tissue neurofibroma. Soft tissue neurofibromas and schwannomas differ by contents of specific types of nerve sheath cells, such as Schwann cells, perineurial cells and CD34+ cells. To compare GIS with these soft tissue lesions, eight cases of typical GIS were studied immunohistochemically to evaluate their nerve sheath cell types. Epithelial membrane antigen (EMA) and claudin-1 as perineurial cell markers, and neurofilament protein as a marker for intratumoral axons were used. In addition, the tumors were stained for cytokeratin, CD117 (C-KIT), alpha-muscle specific actin, S100 protein and CD34. EMA- and claudin-positive cells were seen in 2 (25%) and one lesion, respectively, thus resembling cellular composition of neurofibroma. Intratumoral neurofilament protein positive axons otherwise typical of neurofibroma were found inside 4 tumors (50%). CD34 positivity was found in 6 tumors (75%) and often revealed a diffuse pattern as seen in neurofibroma and not a zonal pattern as described in schwannomas. These results show that GIS has some features that are more typical for neurofibroma than for conventional schwannoma. In surgical pathology practice, a finding of intratumoral axons and positivity for claudin-1 and especially for EMA should not preclude diagnosis of GIS.

A benign neoplasm with histopathological features of both schwannoma and retiform perineurioma (benign schwannoma-perineurioma): a report of six cases of a distinctive soft tissue tumor with a predilection for the fingers

We present six cases of a distinctive soft tissue tumor which occurred in five women and one man. None of the patients had signs of neurofibromatosis. All tumors occurred on the fingers ( n=5) or the thenar eminence of the hand ( n=1). The mean age of the patients was 33 years. The tumors were 1-2.5 cm in diameter (mean size 1.6 cm). Three patients with follow-up were without signs of recurrence or metastasis. Microscopically the lesions were nonencapsulated and featured a multilobular architecture and both myxoid and pseudocystic change. The lobules varied in size and shape and were separated by variably thickened, dense, sclerotic/collagenous septae. The lobules were composed of two components: schwannomatous and perineuriomatous. The schwannomatous component was immunohistochemically S-100 protein positive and CD34 and EMA negative, and the perineuriomatous component had the appearance of retiform perineurioma. The perineurial parts were mostly S-100 protein and CD34 negative and EMA positive. These two components either formed separate nodules or the schwannomatous tissue surrounded the perineurial parts located in the centers of the lobules. We interpreted the lesions as hybrid tumors with features of schwannoma and retiform perineurioma.

Cystic schwannoma of the pancreas

Intrapancreatic schwannoma is a rare neoplasm. We report a case of a 46-year-old man with a cystic schwannoma in the head of the pancreas. This tumor, based on clinical manifestations and radiologic features, was initially suspected to be a cystic mucinous tumor of the pancreas or a pseudocyst. Histologically, the tumor was a typical schwannoma with cyst formation caused by degenerative changes. Immunostaining showed the tumor cells to be strongly and diffusely positive for S-100 protein, vimentin, and CD56, and negative for cytokeratin AE1/AE3, desmin, smooth muscle myosin specific, CD34, and CD117, which support the diagnosis of schwannoma. Cystic schwannoma is a rare neoplasm occurring in the pancreas and should be considered in the differential diagnoses for patients presenting with pancreatic cystic lesions.

Unusual presentation of an abdominoinguinal schwannoma

Schwannoma is a rare, benign peripheral nerve sheath tumor of uncertain origin. This report describes a retroperitoneal cellular schwannoma that extended into the inguinal region. Surgical dissection of a tumor in this site requires an abdominopelvic approach. Histology revealed nodules of pale epithelioid cells separated by fascicles of spindle cells. With immunohistochemistry, no actin was seen. Neurospecific vimentin confirmed the presence of nerve cells. The tumor was completely removed, and as of 6 months later there had been no recurrence. Schwannoma are extremely difficult or even impossible to diagnose preoperatively. If clinicians are faced with an inguinal swelling or herniation and a coexisting abdominal mass, they should perhaps consider radiologic studies that better identify the origin.

Cellular schwannoma: report of a case diagnosed intraoperatively with the aid of cytologic imprints

The diagnosis of cellular schwannoma in intraoperative consultation is difficult because of the hypercellularity and deep location, which may lead to errors. The recognition of cytologic features together with the histological appearance are of great importance to make the correct diagnosis. An accurate diagnosis of this variant of schwannoma is important because other spindle cell tumors display differences in treatment and clinical behavior. We report a demonstrative case of cellular schwannoma arising in retroperitoneum of a 52-yr-old woman in which the cytologic imprints were useful to make an accurate diagnosis intraoperatively. Briefly, the differential diagnosis is discussed.

[Clinicopathological and immunohistochemical analysis of gastrointestinal, urinary and perineal stromal tumors]

OBJECTIVE

To study the histogenesis and pathological characteristics of gastrointestinal stromal tumors (GIST) and GIST type stromal tumor (ST) beyond the gastrointestinal tract.

METHODS

A retrospective study was carried out on leiomyoma, leiomyosarcoma and neurilemoma (46 cases in gastrointestinal tract and l3 cases in urinary tract and perineal area). 4 antibodies (CD117, CD34, SMA, S-100) were used for immunohistochemical staining.

RESULTS

Among 45 cases of GIST, the positive rate of CD117 and CD34 was 93.3% and 88.9% respectively. Among 12 cases of GIST type ST beyond the gastrointestinal tract, the positive rate of CD117 and CD34 was 83.3% and 75.0% respectively. In 2 cases (1 in gastrointestinal tract) of leiomyomas, both CD117 and CD 34 were negative in tumor cells, while SMA was extensively positive.

CONCLUSIONS

CD117 and CD34 positivity are the most valuable factors in diagnosing ST. Both GIST and GIST type ST beyond the gastrointestinal tract are considered originating from a proto-interstitial stem cell with disoriented differentiation.

Neuroblastoma-like schwannoma: a case report and review of the literature

We report a case of schwannoma (neurilemmoma) predominantly composed of small cells arranged in rosettes around central collagenous cores and discuss the differential diagnosis of this unusual variant. Schwannoma with giant rosettes, previously designated as neuroblastoma-like schwannoma by Goldblum et al., must be differentiated from neuroblastoma, peripheral neuroectodermal tumors, and malignant change in a schwannoma.

Retroperitoneal schwannoma with features of gastrointestinal schwannoma. A case report

A case of retroperitoneal schwannoma with histological features of gastrointestinal (GI) schwannoma occurring in a 67-year-old woman is reported. The tumor was composed of spindle cells with focal pseudoatypism and it showed several features typical of gastrointestinal-type schwannoma such as lymphocytic infiltration, peripheral cuff of lymphocytes, lack of Antoni A pattern, and absence of thick walled vessels. Immunohistochemically, the tumor showed diffuse reactivity for S100 protein and glial fibrillary acidic protein. The authors discuss a phenotypical similarity of the lesion with GI schwannoma as well as the possible existence of GI-type schwannoma outside the tubal GI tract.

Schwannoma (neurilemmoma) of the facial nerve presenting as a parotid mass

A 32-year-old male presented with a mass in the parotid gland. Superficial parotidectomy was performed. Histopathologically the tumour was found to be schwannoma (neurilemmoma) and because this is unusual, the case is presented together with the histopathological findings.

Ancient schwannoma arising in a lymph node: report of a case and review of the literature

We report a case of an intranodal schwannoma in a 79-year-old woman. The patient underwent a left colectomy for a colonic adenocarcinoma, with regional lymph node dissection. Macroscopic examination of the specimen revealed a well-circumscribed 4 cm nodule located in the pericolic fat. Macroscopically, it was interpreted as a metastatic lymph node. Microscopically, the nodule was composed of a proliferation of bland spindle cells, was immunohistochemically positive for S100 protein, and negative for smooth muscle actin, desmin, and cytokeratin. The pathological findings led to the diagnosis of a very rare case of primary schwannoma of the lymph node.

[Thalamic intracerebral schwannoma: case report]

The intracranial schwannomas cover about 8% of all the brain tumors, although, those localized inside the encephalic parenchyma are rare only 55 cases being reported in the literature. The histopathologic diagnosis is based on the cellular type and arrangement common to the nervous sheath tumors, the immunohistochemical findings (GFAP, S-100 protein, EMA) and electronmicroscopic findings as well. The clinical presentation related to the intraparenchimatous schwannoma is variable, depending on its localization, the image diagnosis does not show any typical aspect. The surgical treatment is curative once a complete extirpation is obtained. These tumors are benign but one case reported presented malignant signs. We present a patient that had a thalamic schwannoma with histological confirmation. We found no case with this localization in the literature.

Malignant stromal tumor of the gallbladder with interstitial cells of Cajal phenotype

Malignant mesenchymal tumors of the gallbladder are exceedingly rare. We report a malignant stromal tumor of the gallbladder with a phenotype of interstitial cells of Cajal. To our knowledge, only the benign counterpart of this tumor has been described previously. A 34-year-old woman presented with right upper quadrant abdominal pain. At the time of cholecystectomy, the gallbladder was noted to have a thickened wall and a polypoid mass arising in the neck of the gallbladder. Histologic sections showed a cellular proliferation of spindle neoplastic cells that were arranged in short fascicles. Numerous mitotic figures and foci of necrosis were noted. The neoplastic cells expressed CD117 (c-Kit protein) and vimentin. They were negative for smooth muscle actin, desmin, myoglobin, cytokeratin, S100 protein, and CD34. Our case demonstrates that a malignant stromal tumor that is histologically and immunohistochemically identical to gastrointestinal stromal tumor can occur in the gallbladder, and that the expression of CD117 may be of therapeutic importance.