Cellular schwannoma. A clinicopathologic study of 29 cases

Successful management of a rare radius schwannoma mimicking malignant bone tumors: A case report and literature review

Background

Schwannomas are benign tumors originating from Schwann cells, frequently occurring in the spinal cord and peripheral nerves. Intraosseous schwannomas, a rare subset, account for approximately 0.2% of schwannomas. Intraosseous schwannomas commonly impinge the mandible, followed by the sacrum and the spine. By far, only three cases of radius intraosseous schwannomas have been reported in PubMed. The tumor was treated differently in all three cases, resulting in different outcomes.

Case presentation

A 29-year-old male construction engineer who complained of a painless mass on the radial aspect of the right forearm was diagnosed with an intraosseous schwannoma of the radius based on radiography, three-dimensional computed tomography reconstruction, magnetic resonance imaging, pathological examination, and immunohistochemistry. A different surgical approach was employed to reconstruct the radial graft defect using bone microrepair techniques, resulting in more reliable bone healing and early functional recovery. Meanwhile, no clinical and radiographic findings suggestive of recurrence were observed at the 12-month follow-up.

Conclusion

Vascularized bone flap transplantation combined with three-dimensional imaging reconstruction planning might yield better results for repairing small segmental bone defects of the radius caused by intraosseous schwannomas.

Angiomyofibroblastoma and Potential Mimicking Soft Tissue Tumors That May Occasionally Present in the Retroperitoneum: An Approach to the Differential Diagnosis With Report of an Unusual Index Case Abutting the Kidney

The retroperitoneal soft tissues, extending from the pelvic floor to the level of the diaphragm, are the source of a variety of mesenchymal neoplasms with overlapping features and distinct clinical behaviors, making their distinction of crucial importance. Herein, we report a rare retroperitoneal angiomyofibroblastoma (AMFB) that presented as a right abdominal mass in a 25-year-old woman and that clinically simulated a primary renal carcinoma. The patient underwent complete surgical resection showing a well-circumscribed tumor adjacent to but separate from the right kidney. It was comprised of irregular, often anastomosing islands and cords of plump to spindled cells in a collagenous stroma with numerous thin-walled vessels. The tumor cells clustered around the vessels and admixed with moderate numbers of adipocytes. There was neither significant nuclear atypia nor mitotic activity. Immunohistochemically, the tumor cells showed strong reactivity for desmin, diffuse expression of estrogen and progesterone receptors, retained nuclear expression of retinoblastoma protein, and absent CD34 expression. The immunomorphological features were these of a "lipomatous variant" of AMFB of the retroperitoneum. The occurrence of AMFB in the retroperitoneum is unexpected since it mostly develops in the lower genital tract of young women, making its recognition in this rare location difficult. As a consequence, more common pelvic or retroperitoneal soft tissue neoplasms may represent the primary diagnostic considerations. We, therefore, review a variety of soft tissue tumors occurring in the pelvis/retroperitoneum that, to some degree, may mimic AMFB, and present key findings to assist in accurate diagnosis.

Retrospective analysis of the clinical presentation and imaging of eight primary benign mediastinal schwannomas

OBJECTIVE

Mediastinal schwannomas are sometimes confused with other neoplasms during initial radiological studies, especially when there is a history of cancer in another area. In these cases, a more accurate analysis using computed tomography (CT) or even magnetic resonance (MRI) is required. Our study aimed to perform a retrospective analysis of the clinical and imaging features for a series of patients with mediastinal schwannomas that were confirmed by histology and immunohistochemistry.

RESULTS

We found eight patients, five men and three women, with an average age of 51 years for this study. The main signs and symptoms at diagnosis were chest pain, dyspnea, cough, and dysphagia. CT showed that the tumor was located in the posterior compartment of the chest in 7/8 cases. Tumors > 10 cm were more heterogeneous and showed cystic changes. All patients underwent posterolateral thoracotomy, and radiological follow-up showed no evidence of recurrence. Histological analysis was considered the gold standard to confirm diagnosis, along with at least one neurogenic IHC marker. In conclusion, mediastinal schwannomas are benign encapsulated tumors. According to CT, schwannomas > 10 cm show cystic degeneration more frequently. Posterolateral thoracotomy allows complete resection and is considered the surgical approach of choice.

Comparison of pathological, radiological, and prognostic features between cellular schwannoma and non-cellular schwannoma

PURPOSE

To investigate the differences of pathological, radiological, and prognostic features between cellular schwannoma (CS) and non-cellular schwannoma (NCS).

METHODS

CT and MRI images of 24 patients with CSs and 30 patients with NCSs were reviewed retrospectively. Clinico-pathological characteristics of CSs and NCSs and tumor radiological features including location, shape, size, border, cystic-solid components, hemorrhage, calcification, bone remodeling, pattern of CT/MRI precontrast scan, degree of enhancement, target sign, and tumor vessels were recorded. Statistical analyses were performed with Chi square or Fisher's exact test, independent sample t test, and logistic regression analysis to compare the differences between CSs and NCSs.

RESULTS

Four CSs showed mitotic activity, which was not found in the NCS group (P = 0.034). The CS group showed higher MIB-1 index than that in the NCS group (P = 0.002). Two patients with CS presented with tumor recurrence. Compared to NCSs, CSs were often located in spinal area (P = 0.028) and irregular (P = 0.013) with larger size (P = 0.005). Target sign, a common finding in NCSs (7/22, 31.8 %), was not seen in CSs (P = 0.014). The tumor vessels were only seen in CS group (4/22, 18.2 %; P = 0.027). Regression analysis revealed that location (P = 0.048) and size (P = 0.012) were independent indicators in differentiating CSs from NCSs.

CONCLUSIONS

CS is a rare subtype of schwannoma with some significant radiological features including a predilection for the spinal area, irregular shape, large tumor size, absent target sign, tumor vessels, and potential risk of recurrence. Location and size of the schwannomas were the most useful indicators in differentiating CSs from NCSs.

A clinicopathological study of peripheral schwannomas

Aim and objective

Schwannomas are benign neoplasms of neural origin with sporadic or syndromic occurence. They are commonly seen in cranial nerves. Peripheral schwannomas occur rarely and may have unique presentations. The aim of this study is to evaluate the clinico-pathological characteristics of peripheral schwannomas.

Methods

A retrospective cross sectional study of peripheral schwannomas excluding head neck region was conducted. The study group consisted of 18 cases which were recorded over a period of seven years. The corresponding data were collected from the archives of the Department of Pathology.

Results

Male to female ratio was 1:1. The average age of the cases was 47 years. The most common site was the upper limbs (55.55%) followed by lower limbs, chest and penis. The lesions mostly presented as painless swellings (62%). Histopathological examination revealed classic features of schwannoma. Secondary changes included cystic degeneration, foam cells, epitheloid cells, hyalinization, microcystic change and collection of plasma cells. All cases were confirmed by positive S100 staining.

Conclusion

Peripheral schwannomas may be missed due to its rarity and atypical presentations. Both clinicians and pathologists should be aware of this common entity at unusual sites for the proper management of the patients. Surgery is usually the treatment of choice.

Benign peripheral nerve tumors

Benign peripheral nerve tumors encompass a wide range of neoplasms and non-neoplastic tumor like lesions. Some of these lesions if not encountered in the setting of genetic syndromes, are occurring sporadically. The principles of oncology should be respectfully followed in every step of diagnostic approach and surgical management. Albeit, classified as benign, some of them do have different level of malignant potential, thus the treating physicians should be aware of that to avoid possible pitfalls with devastating outcomes. This article reviews the most common benign peripheral nerve tumors discussing the clinicopathological findings, imaging appearance and the current trend in their approach.

Intracranial cellular schwannomas: a clinicopathological study of 20 cases

AIMS

Cellular schwannoma is a specific subtype of schwannoma, prone to misinterpretation as a malignant neoplasm. Involvement of the intracranial compartment by these tumours is extremely rare. We aim to characterise this clinicopathological subgroup.

METHODS AND RESULTS

We identified a total of 20 cellular schwannomas with predominant intracranial involvement. The mean age of the patients at the time of surgery was 37 years (range = 16-81), with a slight female predominance (1.5:1 ratio). The most common sites were the eighth (n = 8) and fifth (n = 6) cranial nerves. Three tumours involved the anterior cranial fossa/olfactory groove, and a single case involved the glossopharyngeal nerve. All tumours met established criteria for cellular schwannoma, and were composed of interlacing fascicles of spindle cells lacking Verocay bodies with minimal Antoni B pattern and variable chronic inflammation and foamy histiocytes. Rare findings included haemosiderin deposition (n = 6), necrosis (n = 4), brisk mitotic activity (>10 mitoses per 10 high-power fields) (n = 2), focal epithelioid morphology (n = 2), myxoid areas (n = 2), neuroblastoma-like pattern (n = 1) and granular cells (n = 1). Immunohistochemical stains demonstrated expression of Schwann cell markers (S100 protein, SOX10, collagen IV) and preserved H3 K27 trimethylation in all cases tested. Fourteen patients had postoperative follow-up, ranging from 2 months to 21 years (mean = 66 months). In patients with follow-up, local recurrence/persistence developed in six cases; five tumours were initially incompletely resected. No metastatic disease or deaths were reported.

CONCLUSIONS

Intracranial cellular schwannomas share morphological and immunophenotypical features with cellular schwannomas at others sites may demonstrate locally aggressive growth but appear to lack metastatic potential.

What's new in nerve sheath tumors

Peripheral nerve sheath tumors are commonly encountered and frequently pose challenges to the pathologist and the clinician. This review discusses the wide range of entities with an emphasis on new discoveries in the past decade. Clinical, histologic, immunohistochemical, and pathogenetic findings are discussed with an emphasis on clinical implications and differential diagnosis.

Clinicopathological variables of sporadic schwannomas of peripheral nerve in 291 patients and expression of biologically relevant markers

OBJECTIVE While sporadic peripheral schwannomas (SPSs) are generally well treated with surgery, their biology is not well understood. Consequently, treatment options are limited. The aim of this study was to provide a comprehensive description of SPS. The authors describe clinicopathological features and treatment outcomes of patients harboring these tumors, and they assess expression of biomarkers using a clinically annotated tissue microarray. Together, these data give new insight into the biology and management of SPS. METHODS Patients presenting with a primary SPS between 1993 and 2011 (n = 291) were selected from an institutional registry to construct a clinical database. All patients underwent follow-up, and short- and long-term outcomes were assessed. Expression of relevant biomarkers was assessed using a new tissue microarray (n = 121). RESULTS SPSs were generally large (mean 5.5 cm) and frequently painful at presentation (55%). Most patients were treated with surgery (80%), the majority of whom experienced complete resolution (52%) or improvement (18%) of their symptoms. Tumors that were completely resected (85%) did not recur. Some patients experienced short-term (16%) and long-term (4%) complications postoperatively. Schwannomas expressed higher levels of platelet-derived growth factor receptor-β (2.1) than malignant peripheral nerve sheath tumors (MPNSTs) (1.5, p = 0.004) and neurofibromas (1.33, p = 0.007). Expression of human epidermal growth factor receptor-2 was greater in SPSs (0.91) than in MPNSTs (0.33, p = 0.002) and neurofibromas (0.33, p = 0.026). Epidermal growth factor receptor was expressed in far fewer SPS cells (10%) than in MPNSTs (58%, p < 0.0001) or neurofibromas (37%, p = 0.007). SPSs more frequently expressed cytoplasmic survivin (66% of tumor cells) than normal nerve (46% of cells), but SPS expressed nuclear survivin in fewer tumor cells than in MPNSTs (24% and 50%, respectively; p = 0.018). CONCLUSIONS Complete resection is curative for SPS. Left untreated, however, these tumors can cause significant morbidity, and not all patients are candidates for resection. SPSs express a pattern of biomarkers consistent with the dysregulation of the tumor suppressor merlin observed in neurofibromatosis Type 2-associated schwannomas, suggesting a shared etiology. This SPS pattern is distinct from that of other tumors of the peripheral nerve sheath.

Syntaxin-4 and SNAP23 act as exocytic SNAREs to release NGF from cultured Schwann cells

Nowadays peripheral nerve (PN) injury occurs more frequently, the outcome is often poor because of the ineffective treatment. Once the PN was injured, Schwann cells (SCs) release neurotrophins to guide the regeneration of axons. Recent researches revealed the duration of NGF administration acts a positive role during the nerve regeneration, but the molecular mechanisms of NGF release from SCs are unknown. To investigate components of the exocytic machinery of NGF, we used RT-PCR, Western blot and immunocytochemistry to investigate expressions and locations of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) in rat primary cultured SCs. We found that Syntaxin-4 and SNAP23 were co-localized with NGF by immunocytochemistry. Co-immunoprecipitation (Co-IP) and RNA interference (RNAi) confirmed Syntaxin-4 associated with SNAP23 to regulate the release of NGF from SCs. Knockdown of Syntaxin-4 and SNAP23 dramatically decreased the exocytosis of NGF and inhibited the neurite outgrowth of dorsal root ganglia (DRG). Syntaxin-4 and SNAP23 acted as exocytic SNAREs to release NGF from SCs.

Practical Issues for Retroperitoneal Sarcoma

Background

Retroperitoneal sarcoma is rare. Using initial specimens on biopsy, a definitive diagnosis of histological subtypes is ideal but not always achievable.

Methods

A retrospective institutional review was performed for all cases of adult retroperitoneal sarcoma from 1996 to 2015. A review of the literature was also performed related to the distribution of retroperitoneal sarcoma subtypes. A meta-analysis was performed.

Results

Liposarcoma is the most common subtype (45%), followed by leiomyosarcoma (21%), not otherwise specified (8%), and undifferentiated pleomorphic sarcoma (6%) by literature review. Data from Moffitt Cancer Center demonstrate the same general distribution for subtypes of retroperitoneal sarcoma. A pathology-based algorithm for the diagnosis of retroperitoneal sarcoma is illustrated, and common pitfalls in the pathology of retroperitoneal sarcoma are discussed.

Conclusions

An informative diagnosis of retroperitoneal sarcoma via specimens on biopsy is achievable and meaningful to guide effective therapy. A practical and multidisciplinary algorithm focused on the histopathology is helpful for the management of retroperitoneal sarcoma.

Selected benign cutaneous lesions that may simulate melanoma histologically

As cutaneous melanomas manifest a wide spectrum of clinical and pathologic presentations, several other lesions enter into their differential diagnosis. This article considers those entities, including melanocytic hyperplasia, cellular nodules in congenital nevi, atypical lentiginous melanocytic proliferations, "special site" nevi, epithelioid histiocytoma, neurothekeoma, cellular schwannoma, and proliferating scars.

Peripheral Nerve Sheath Tumors

This article presents an overview of the diagnostic categories of benign and malignant nerve sheath tumors, including neuroma, neurofibroma, nerve sheath myxoma, perineurioma, schwannoma, and malignant peripheral nerve sheath tumor. The discussion emphasizes histologic patterns; ancillary studies, such as immunohistochemistry; and differential diagnoses. The information is of value to practicing pathologists in both community and academic settings.

Mesenchymal tumours of the mediastinum--part II

This is the second part of a two-part review on soft tissue tumours which may be encountered in the mediastinum. This review is based on the 2013 WHO classification of soft tissue tumours and the 2015 WHO classification of tumours of the lung, pleura, thymus and heart and provides an updated overview of mesenchymal tumours that have been reported in the mediastinum.

Cutaneous microcystic/reticular schwannoma: a poorly recognized entity

BACKGROUND

Microcystic/ reticular schwannoma is exceptionally rare yet distinctive morphological variant of schwannoma with predilection for visceral sites lacking association with neurofibromatosis.

AIMS

To further delineate clinicopathological features of cutaneous microcystic/reticular schwannoma and to discuss its differential diagnosis.

RESULTS

We analyzed three cutaneous microcystic/reticular schwannomas, occurring in two males and one female (mean age: 37.6 years). The tumors presented as a non-painful slightly raised papule (mean: 0.7 cm) on upper arm (n = 2) and back (n = 1). No recurrences were observed despite marginal excision (mean follow up: 42 months). Histopathologically, a multilobular proliferation was present in the dermis composed of bland tumor cells forming distinctive microcystic, reticular, lace-like or pseudoglandular structures, containing abundant myxoid/mucinous material. By immunohistochemistry, tumor cells lining microcystic structures corresponded to Schwann cells (diffuse S100 positive, variable GFAP positivity). A discontinuous EMA-positive perineurium was present at the periphery of some of the lobules.

CONCLUSION

Cutaneous microcystic/reticular schwannoma expands the spectrum of benign peripheral nerve sheath tumors with reticular morphology encountered in the skin. Other tumors in this group include reticular perineurioma and hybrid tumors with reticular morphology, e.g. reticular perineurioma/schwannoma and reticular perineurioma/neurofibroma.

Results of surgical treatment of schwannomas arising from extremities

Schwannomas are benign neoplasms derived from Schwann cells. In this work, we present our experience in operative management of schwannomas and analyse results of treatment. Clinical material consisted of 34 patients, in whom 44 schwannomas located in extremities were excised between 1985 and 2013. Thirty-five tumours originated from major peripheral nerves and 9 from small nerve branches. Postoperatively, in the first group of tumours, pain resolved in 100%, paresthesias in 83.3%, and Hoffmann-Tinel sign in 91.6% of the patients. Improvement in motor function was noted in 28.5% of the cases, in sensory function: complete in 70%, and partial in 15%. The most frequently affected major peripheral nerves were the ulnar (11 tumours) and median (5 tumours) nerves. Schwannomas originating from small nerve branches were removed without identification of the site of origin. After their resection, definitive healing was achieved. Conclusions. (1) Schwannomas located in extremities arise predominantly from major peripheral nerves, most commonly the ulnar and median nerves. (2) Gradual tumour growth causes exacerbation of compression neuropathy, creating an indication for surgery. (3) In most cases, improvement in peripheral nerve function after excision of schwannoma is achieved. (4) The risk of new permanent postoperative neurological deficits is low.

Results of surgical treatment of schwannomas arising from extremities

Schwannomas are benign neoplasms derived from Schwann cells. In this work, we present our experience in operative management of schwannomas and analyse results of treatment. Clinical material consisted of 34 patients, in whom 44 schwannomas located in extremities were excised between 1985 and 2013. Thirty-five tumours originated from major peripheral nerves and 9 from small nerve branches. Postoperatively, in the first group of tumours, pain resolved in 100%, paresthesias in 83.3%, and Hoffmann-Tinel sign in 91.6% of the patients. Improvement in motor function was noted in 28.5% of the cases, in sensory function: complete in 70%, and partial in 15%. The most frequently affected major peripheral nerves were the ulnar (11 tumours) and median (5 tumours) nerves. Schwannomas originating from small nerve branches were removed without identification of the site of origin. After their resection, definitive healing was achieved. Conclusions. (1) Schwannomas located in extremities arise predominantly from major peripheral nerves, most commonly the ulnar and median nerves. (2) Gradual tumour growth causes exacerbation of compression neuropathy, creating an indication for surgery. (3) In most cases, improvement in peripheral nerve function after excision of schwannoma is achieved. (4) The risk of new permanent postoperative neurological deficits is low.

A recurrent cellular schwannoma

Cellular schwannoma is an uncommon variant of schwannomas that can occur in a peripheral nerve. Although cellular schwannomas typically do not differ in prognosis from regular schwannomas, they are known to cause local recurrence when not completely resected. Here, we report the case of a patient with cellular schwannoma of the posterior mediastinum, which recurred after 13 years.

Challenging epithelioid mesenchymal neoplasms: mimics and traps

Epithelioid mesenchymal malignancies represent a major diagnostic challenge. Epithelioid morphology can be observed in a variety of soft tissue neoplasms, however there exist specific subtypes in which an epithelioid apperance constitutes the most distinctive morphological feature. Moving from epithelioid sarcoma of Enzinger (the prototype of sarcoma with epithelioid morphology), this review will focus on the most relevant entities: namely epithelioid haemangioendothelioma and angiosarcoma, pseudomyogenic haemangioendothelioma, epithelioid malignant peripheral nerve sheath tumour, epithelioid sclerosing fibrosarcoma, epithelioid pleomorphic liposarcoma, alveolar soft part sarcoma, and undifferentiated soft tissue sarcoma with epithelioid morphology. Differential diagnoses and major pitfalls will be discussed in detail.

Infantile cellular schwannoma developing on the skin with atypical clinical features

Cellular schwannoma (CS) is a variety of schwannoma with a predominantly cellular growth, normally developing in middle-aged patients. In this report, we describe a 15-month-old infant with primary cutaneous CS on the knee. Because of its histologically malignant features, CS is sometimes overdiagnosed as a malignant nerve tumor. Therefore, awareness of this variant of schwannoma is important for dermatologists to avoid needless treatments for patients with CS.

Primary pleural hybrid cellular schwannoma/perineurioma: a case report

Hybrid schwannoma/perineurioma is a recently characterized benign nerve sheath tumor, most commonly affecting the lower limb and limb girdle. Hybrid tumors located in the subcutis of the trunk have not previously been reported to affect the pleura. We describe a 52-year-old man with dyspnea and thoracic pain due to a large mass in the right pleura, histologically composed of densely packed, S-100-positive spindle cells, intermixed with cells containing slender nuclei positive for epithelial membrane antigen, Glut-1, and claudin-1. To our knowledge, this is the first report of hybrid schwannoma/perineurioma in the pleura.

Atypical presentation of sinonasal cellular schwannoma: a nonsolitary mass with osseous, orbital, and intracranial invasion

Objective Sinonasal cellular schwannoma represents < 4% of head and neck schwannomas. These benign tumors are typically confined to the nasal cavity or ethmoid sinus. We describe an atypical case of sinonasal cellular schwannoma with diffuse paranasal sinus involvement and both intraorbital and intracranial extension.

Results A 62-year-old woman presented with a 6-month history of right orbital proptosis and right-sided headache. Subsequent imaging revealed an invasive paranasal sinus mass extending through the skull base and displacing the right orbit. Preoperative biopsies were not diagnostic but revealed a spindle cell lesion suspicious for malignancy based on lack of encapsulation, infiltration of the sinonasal submucosa, and osseous invasion. The patient underwent open skull base surgery, and pathology confirmed a S100-positive nonencapsulated cellular schwannoma.

Conclusion An atypical case of sinonasal cellular schwannoma with intracranial extension is reported. Its presentation is contrary to the common view that these are isolated solitary lesions of the nasoethmoid region. We suggest that sinonasal cellular schwannoma be considered in the differential diagnosis of a poorly defined invasive paranasal sinus mass, particularly following biopsy.

Cellular schwannoma arising from the gastric wall misdiagnosed as a gastric stromal tumor: A case report

Cellular schwannomas have been previously described at almost every anatomic location of the human body, but reports in the gastric wall are rare. The current study presents a rare case of cellular schwannoma originating from the gastric wall. Computed tomography revealed a 5.6×5.3×4.0-cm³ solid mass located in the posterior wall of the stomach. Open laparotomy confirmed its mesenchymal origin. Microscopically, the tissue was composed of spindle-shaped and fascicularly-arranged cells, but mitotic figures were rare. Immunohistochemical staining showed that the tumor was negative for cluster of differentiation (CD)117, CD34, smooth muscle actin and desmin, but positive for S-100 and Ki67. The patient presented no evidence of recurrence and metastasis during follow-up. Gastric cellular schwannomas may be diagnosed by clinical characteristics, histological observations and immunohistochemical markers.

Cellular schwannoma masquerading as malignant peripheral nerve sheath tumour: a diagnostic dilemma

We present a case of a 15-year-old girl with a pulsatile, rapidly enlarging mass at the root of the nose suspected to be malignant. Excisional biopsy showed worrisome histological features; however, a final diagnosis of cellular schwannoma was reached excluding the possibility of malignant peripheral nerve sheath tumour by histological and immunohistochemical attributes. Cellular schwannoma, a pseudosarcomatous entity, is a rare benign neoplasm that may cause bone erosion and may be mistaken for a malignancy, clinically and histologically. Diagnosis of cellular schwannoma is essential to prevent mismanagement as it never metastasises and responds to local excision as opposed to aggressive treatment required by a malignant neoplasm.

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.

Retroperitoneal schwannoma is characterized by a high incidence of cellular type and GFAP-immunoreactivity

To clarify the clinicopathologic characteristics of retroperitoneal schwannomas, which are sometimes confused with other spindle cell tumors, 27 cases were studied microscopically and immunohistochemically. The 27 cases consisted of 17 females and 10 males, the ages of whom ranged from 31-79 (mean 57.4) years. Gross examination revealed well-demarcated, encapsulated tumors, 3-15 cm (mean 8 cm) in diameter. Microscopic review divided them into 13 cases of cellular/fascicular, 3 of conventional, 6 of intermediate, and 5 of ancient type. Cellular/fascicular schwannomas were composed of cellular fascicles of spindle cells, in which nuclear palisading, Antoni B area and cyst were unclear, while numerous foamy cells were intermingled. Immunohistochemical investigation revealed diffuse, strong positivity for S-100 protein and Sox10 in all tumors studied. In addition, glial fibrillary acidic protein (GFAP) was extensively expressed in 92% of the cellular/fascicular type, while it was less prominent in others. The present study suggests that retroperitoneal schwannoma often occurs in the middle-aged woman, grows to a large size, exhibits cellular/fascicular microscopic features in half of the cases, and may arise from GFAP-positive Schwann cells. The presence of hyalinized vessels and dense infiltration of foamy macrophages as well as diffuse immunoreactivity for S-100 protein and Sox10 are helpful for the differential diagnosis.

Soft Tissue Pseudosarcomas

Soft tissue pathology is one of the most challenging areas of diagnostic pathology, not only because of the morphologic diversity of such lesions, but also because of their rarity and pathologists' subsequent lack of exposure to these tumors. Many lesions mimic malignant mesenchymal neoplasms, collectively referred to as "pseudosarcomas." The list of proliferations that can simulate a sarcoma is extensive and heterogeneous. This review addresses malignant, nonmesenchymal neoplasms; mesenchymal neoplasms that histologically mimic sarcomas but are benign; and benign reactive soft tissue lesions that are neither neoplastic nor malignant, but have worrisome clinical and/or morphologic features.

Soft tissue tumours of the retroperitoneum

Purpose. This review summarizes the more prevalent soft tissue tumours arising in the retroperitoneum and highlights some recent fundamental and diagnostic developments relevant to mesenchymal tumours.

Discussion. The retroperitoneum is an underestimated site for benign and malignant neoplastic disease, and represents the second most common site of origin of primary malignant soft tissue tumours (sarcomas) after the deep tissues of the lower extremity. In contrast to the predominance of benign soft tissue lesions over malignant sarcomas elsewhere, retroperitoneal mesenchymal lesions are far more likely to be malignant. The differential diagnosis is primarily with the more common lymphoproliferative and parenchymatous epithelial lesions arising in this area, and with metastatic disease from known or unknown primary sites elsewhere.The most prevalent mesenchymal tumours at this site are of a lipomatous, myogenic or neural nature.Their generally late clinical presentation and poorly accessible location provides numerous clinical challenges; optimal radiological imaging and a properly performed biopsy are essential cogs in the management route. Histopathological diagnosis may be complicated, but has been aided by developments in the fields of immunohistochemistry and tumour (cyto)genetics. Despite significant advances in oncological management protocols, the prognosis remains generally less favourable than for similar tumours at more accessible sites.

A case of fibroblastic low-grade malignant peripheral nerve sheath tumor--a true neurofibrosarcoma

The authors report a case of low-grade retroperitoneal malignant peripheral nerve sheath tumor (MPNST) showing Schwannian and fibroblastic differentiation in individual tumor cells. The tumor was detected in a 29-year-old male and posed diagnostic difficulty because of the unusual morphologic and immunophenotypic features. Morphologic examination of the H&E sections revealed a rather circumscribed, highly vascular, moderately cellular spindle cell tumor. The neoplastic cells were arranged in vague, short fascicles, distributed haphazardly amid hemangiopericytoma-like vascular channels, and showed occasional whorls. Myxoid stroma and keloid-like collagen bundles were frequently seen. There were satellite nodules outside the main tumor mass and low mitotic activity but no necrosis. The tumor cells stained strongly and diffusely for both S-100 protein and CD34. Electron microscopy revealed cells with processes and focal lamina, and prominent rough endoplasmic reticulum. Although the capacity of MPNST to exhibit divergent differentiation is well known, fibroblastic differentiation is generally poorly and inconsistently documented. The present case represents an unambiguous demonstration of the co-expression within individual tumor cells of Schwannian and fibroblastic differentiation in a low-grade MPNST. The literature on this subject is reviewed.

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

Classic cytogenetics has evolved from black and white to technicolor images of chromosomes as a result of advances in fluorescence in situ hybridization (FISH) techniques, and is now called molecular cytogenetics. Improvements in the quality and diversity of probes suitable for FISH, coupled with advances in computerized image analysis, now permit the genome or tissue of interest to be analyzed in detail on a glass slide. It is evident that the growing list of options for cytogenetic analysis has improved the understanding of chromosomal changes in disease initiation, progression, and response to treatment. The contributions of classic and molecular cytogenetics to the study of brain tumors have provided scientists and clinicians alike with new avenues for investigation. In this review the authors summarize the contributions of molecular cytogenetics to the study of brain tumors, encompassing the findings of classic cytogenetics, interphase- and metaphase-based FISH studies, spectral karyotyping, and metaphase- and array-based comparative genomic hybridization. In addition, this review also details the role of molecular cytogenetic techniques in other aspects of understanding the pathogenesis of brain tumors, including xenograft, cancer stem cell, and telomere length studies.

Clonal chromosome abnormalities in a plexiform cellular schwannoma

Cellular schwannomas are uncommon tumors of Schwann cells that can rarely have a plexiform architecture. Cellular schwannomas can be confused with low-grade malignant peripheral nerve sheath tumors (MPNST) but have been noted to have a benign clinical course. There are few published cytogenetic analyses of cellular schwannomas and, to our knowledge, there are no reports of the plexiform variant of cellular schwannoma to date. Cellular schwannomas are reported to have cytogenetic changes similar to those seen in benign schwannomas with near-diploid karyotypes having simple numerical changes often involving chromosomes 22, 7, and the sex chromosomes. MPNST are markedly different, with extensive genetic heterogeneity and complex karyotypes. We report clonal numerical changes in a cellular schwannoma with plexiform architecture: 47,XY,+17 and 48,XY,+17,+18. These findings add to the karyotypic spectrum of peripheral nerve sheath tumors.

Immunohistochemical and Ultrastructural Comparative Study of External Lamina Structure in 31 Cases of Cellular, Classical, and Melanotic Schwannomas

Unlike most soft tissue tumors, schwannoma is characterized by the presence of distinct linear, frequently duplicated external lamina (EL). Although electron microscopy remains the gold standard for demonstrating this unique feature and distinguishing its morphologic variants from mimickers, the use of two anti-EL antibodies, laminin and type IV collagen, appears to supersede electron microscopy in terms of current practice. To determine whether immunohistochemical expression correlates with ultrastructural findings, 10 cellular schwannomas, 18 classic schwannomas, and 3 melanotic schwannomas were evaluated ultrastructurally and immunohistochemically using antibodies to type IV collagen and laminin. Immunohistochemically, a moderate to strong intensity in more than 50% of tumor cells was detected using either antibody in most cases of cellular schwannomas (70%), the Antoni A areas of classic schwannomas (78%), and melanotic schwannomas (67%). Ultrastructurally, the presence of diffusely continuous, duplicated EL was observed in 30% of cellular schwannomas and 56% of classic schwannomas, while 50% of cellular schwannomas and 22% of classic schwannomas showed either continuous simple EL or discontinuous but duplicated EL alone. In addition, two cellular schwannomas (20%) and four classic schwannomas (22.2%) had only a simple layer of EL in focal areas. In contrast to the distinct immunostaining surrounding individual cells seen in the former two subtypes, all three melanotic schwannomas displayed a biphasic-staining pattern of the EL (ie, individual cell and nested), which was confirmed at the ultrastructural level. The authors found a significant difference in intensity between the Antoni A and B areas of classic schwannomas using both laminin and type IV collagen. In addition, the intensities of laminin and type IV collagen in the Antoni A areas of classic schwannomas were significantly stronger compared with those of cellular schwannomas. Nevertheless, there was no significant difference either between two antibodies or between cellular and classic variants with regard to the extent of immunoreaction. Only in classic schwannomas did the extent of immunoreaction against both laminin and type IV collagen correlate significantly with the ultrastructural EL distribution pattern (diffusely continuous vs. discontinuous). However, this association was not detected in cases of cellular schwannomas. On the other hand, the intensities of laminin and type IV collagen did not correlate with the ultrastructural thickness of EL, irrespective of the morphologic subtypes. In conclusion, both type collagen IV and laminin are still reliable markers of EL in various types of schwannomas. Schwannomas exhibiting a monolayered EL are as strong in immunoreaction as those displaying reduplicated/thickened EL, indicating that a single layer of EL is thick enough to be identified by both antibodies with sufficient sensitivity. The peculiar biphasic EL pattern seen in melanotic schwannoma remains under-recognized, which may lead to misdiagnosis as malignant melanomas, especially in limited biopsy specimens.

Cellular schwannoma: a rare spinal benign nerve-sheath tumor with a pseudosarcomatous appearance: case report

We report a case of cellular schwannoma, a rare benign nerve-sheath tumor in a 27 year-old woman. It was presented as a voluminous lesion in the paraspinal region that caused lumbar vertebral body destruction. These features, in association to the microscopic aspects of a hypercellular, pleomorphic neoplasm may lead to a false impression of a malignant tumor. Therefore, it is important to have an accurate examination to confirm the benign nature of this tumor thus avoiding unnecessary therapy.

A rare case of cellular schwannoma involving the trigeminal ganglion

Cellular schwannomas rarely involve the cranial nerves, being more common in the spinal and peripheral nerves. A rare case of cellular schwannoma involving the gasserian ganglion, a hitherto unreported site, that extended infratentorially to present as a cerebellopontine angle tumor is reported. It is important to recognize that cellular schwannomas can histologically mimic malignant peripheral nerve sheath tumors because of their high cellularity and mitotic activity, but they are relatively benign tumors with a tendency to recur but not metastasize.

Retrobulbar cellular schwannoma. Two cases report and review of the literature

Cellular schwannoma is a variant of classical schwannoma that is characterized by high cellularity. As it is accompanied by mitotic figures, it is easily mistaken for a malignant neoplasm. However, hyalinized thick-walled blood vessels, an alternating growth pattern of spindle-shaped neoplastic cells, and even Verocay bodies can be found. It is most commonly seen in the paravertebral area, particularly in the mediastinum and retroperitoneum. Retrobulbar cellular schwannoma is uncommon, and only one case has been reported to date. In this study, we report two additional cases of retrobulbar cellular schwannoma that recurred two years after surgery. We suggest that the patient be given an aggressive postoperative treatment because a successful, complete excision cannot be guaranteed at such an anatomic site.

Congenital and childhood plexiform (multinodular) cellular schwannoma: a troublesome mimic of malignant peripheral nerve sheath tumor

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.

Presacral multiple cellular schwannomas

STUDY DESIGN

Case report. The authors documented a patient presenting with multiple cellular schwannomas along the sciatic nerve. The patient had no stigmas of neurofibromatosis. Thirteen tumors were resected via both anterior and posterior approaches.

OBJECTIVES

To point out that presacral cellular schwannoma can display multiple occurrences.

SUMMARY OF BACKGROUND DATA

Cellular schwannoma, which is a well-recognized variant of benign schwannoma, is often misdiagnosed as sarcoma. The tumor is usually a solitary lesion.

MATERIALS AND METHODS

Medical history, physical findings, imaging features, and histologic findings were reviewed in a case of multiple cellular schwannomas in the presacral regions.

RESULTS

A 39-year-old woman without any evidence of neurofibromatosis underwent removal of presacral multiple tumors along the sacral nerve root. Nineteen years after the surgery, the tumors recurred with multiple fashion. Thirteen tumors were resected via both anterior and posterior approaches. Immunohistochemical analysis of S-100 protein and Ki-67 were beneficial with respect to differentiation of cellular schwannoma from malignant peripheral nerve sheath tumor.

CONCLUSIONS

The present case illustrated that multiple cellular schwannomas can develop in nonneurofibromatosis patients.

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.

Cellular schwannoma in the oral mucosa

A case of cellular schwannoma of the oral mucosa in a 34-year-old Japanese man is described. Cellular schwannoma commonly affects soft tissues such as the retroperitoneum and posterior mediastinum, and also bone, but is extremely rare in the oral region. To our knowledge, this is only the second report of oral cellular schwannoma. Histologically, the tumor parenchyma consisted of hypercellular spindle cells with nuclear and cytoplasmic pleomorphism and nuclear palisading resembling Antoni A-type conventional schwannoma, without evidence of Verocay bodies. These features were indicative of cellular schwannoma. Immunohistochemically, the tumor cells were positive for S-100, S-100alpha, S-100beta and vimentin, suggesting that they were of peripheral nervous origin. Furthermore, it is speculated that the tumor was intermediate between a benign and a malignant state, based on the histological features and positivity for S-100alpha.

Abnormal pigmentation of schwannoma attributed to excess production of neuromelanin-like pigment

Five cases of non-melanotic pigmented schwannoma with excess accumulation of neuromelanin are presented. The tumors were composed basically of spindle or fusiform tumor cells, compatible with those of classical schwannoma, together with varying numbers of tumor cells containing various amounts of light brown or grayish pigment. Fontana-Masson stain demonstrated argentaffin granules in some tumor cells of each tumor and bleaching with potassium permanganate abolished argentaffin reaction. Ultrastructural examination demonstrated the granules contained fine particles with heterogeneous density, occasionally together with coarse granular materials or amorphous high-density areas, indicating lysosome or autophagosome. Neither typical melanosomes nor neurosecretory granules were detected. In immunohistochemistry, neurogenic markers as well as CD68 were expressed in most tumor cells in each case and various numbers of tumor cells were positive for Leu7 and CD34. Lysozyme was also frequently positive in tumor cells, especially in granular cells. HMB45 was not expressed in any of the cases. These findings indicate that these cases are schwannomas with abnormal accumulation of neuromelanin-like pigment.

Cellular schwannoma mimics a sarcoma: an example of a potential pitfall in aspiration cytodiagnosis

Cellular schwannoma, a variant of benign schwannoma, is characterized by marked nuclear pleomorphism and hyperchromasia and may be overdiagnosed as a malignancy in fine-needle aspiration specimens. We report the aspiration cytology findings of a case of cellular schwannoma that arose in the parapharyngeal region of a 50-yr-old woman.

Benign epithelioid schwannoma

Benign schwannoma (neurilemoma) has various morphologic patterns that may cause problems in differential diagnosis. Although an epithelioid variant of malignant schwannoma simulating carcinoma and melanoma is well recognized, a benign counterpart has not yet been defined. In the current study, we describe five cases of benign epithelioid schwannoma that were in the subcutis (four cases) and the neck of the urinary bladder (one case). The tumors occurred in adults 28-73 years of age, were 1-4.5 cm in diameter, were well circumscribed and cellular, and were composed of epithelioid cells arranged in cords and nests. The benign nature of the lesions was evident by a constellation of features, including small size, sharp circumscription, bland morphology, low proliferative activity (four of five had < or =1% Ki67 immunostaining), and a benign clinical course after either marginal or intralesional excision. All cases had some features of classic schwannoma light microscopically and a high degree of Schwann cell differentiation both ultrastructurally and immunohistochemically. The recognition of benign epithelioid schwannoma is important because it may be misinterpreted as a malignant neuroectodermal, mesenchymal, epithelioid, or melanocytic tumor.

Subdiaphragmatic and intrathoracic paraspinal malignant peripheral nerve sheath tumors: a clinicopathologic study of 25 patients and 26 tumors

BACKGROUND

To determine the effects of anatomic site on the presentation and diagnosis of malignant peripheral nerve sheath tumors (MPNSTs) and on the treatment and outcomes of the patients, the authors initiated a study of these tumors at different sites. An earlier report described MPNSTs of the buttock and lower extremity, and the current series analyzes those presenting at intrathoracic (IT) and subdiaphragmatic (SD) paraspinal sites.

METHODS

The authors reviewed data on patients with paraspinal MPNSTs who were seen at Memorial Hospital during the period 1960-1995 and for whom histologic slides were available. Various clinicopathologic parameters and their effects on patient outcomes were examined.

RESULTS

Twenty-five patients with 26 tumors were evaluated. Seven tumors were IT and 19 were SD; 60% of the patients had neurofibromatosis type 1 (NF1). Most patients presented with pain, and a diagnostic delay (of 3 months to 2 years) was often noted. Mean tumor sizes for SD and IT tumors were 14.3 cm and 6.6 cm, respectively. Most MPNSTs were composed of spindle cells in fascicles. Twenty-seven percent exhibited divergent differentiation. Twenty-four tumors were high grade, and a low grade component was identified in 8 tumors. Surgical resection was attempted for 23 tumors (88%), but complete resection was achieved in only 6 cases (23%). Eighty percent of the patients died of their tumors, 2-year and 5-year survival rates were 35% and 16%, and median survival was 8.5 months. Significant prognostic factors were tumor size <5 cm, the presence of a low grade component, and complete tumor resection.

CONCLUSIONS

Paraspinal MPNSTs have more aggressive behavior than peripherally located tumors, mainly because of the difficulty encountered in resecting them completely. Prognoses of patients with MPNST at this site appear to be affected by resection status, tumor size, and tumor grade.