[Gastric gastrointestinal stromal tumour and schwannoma: An unusual presentation in a patient without neurofibromatosis]. / Tumor del estroma gastrointestinal y schwannoma gástricos: una presentación inusual en un paciente sin 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.

Recurrent SMARCB1 Inactivation in Epithelioid Malignant Peripheral Nerve Sheath Tumors.

Epithelioid malignant peripheral nerve sheath tumors (EMPNST) are characterized by diffuse S-100 and SOX10 positivity, frequent immunohistochemical loss of SMARCB1 expression (70%), and rare association with neurofibromatosis type 1. Some cases arise in a preexisting epithelioid schwannoma (ESCW), which also show SMARCB1 loss in 40% of cases. To date, little is known about the genomic landscape of this distinctive variant of malignant peripheral nerve sheath tumor. The aim of this study was to use targeted next-generation sequencing to identify recurrent genomic aberrations in EMPNST and a subset of ESCW, including the basis of SMARCB1 loss. Sixteen EMPNSTs (13 SMARCB1-lost, 3 SMARCB1-retained) and 5 ESCWs with SMARCB1 loss were selected for the cohort. Sequencing identified SMARCB1 gene inactivation in 12/16 (75%) EMPNST and all 5 (100%) ESCW through homozygous deletion (N=8), nonsense (N=7), frameshift (N=2), or splice site (N=2) mutations; 2 EMPNSTs harbored 2 concurrent mutations each. SMARCB1 immunohistochemistry status and SMARCB1 alterations were concordant in 20/21 of the sequenced tumors. Additional genetic alterations in a subset of EMPNST included inactivation of CDKN2A and gain of chromosome 2q. Among SMARCB1-wild-type EMPNSTs there were single cases each with NF1 and NF2 mutations. No cases had SUZ12 or EED mutations. In summary, we identified recurrent SMARCB1 alterations in EMPNST (and all 5 SMARCB1-negative ESCWs tested), supporting loss of SMARCB1 tumor suppressor function as a key oncogenic event. SMARCB1-retained EMPNSTs lack SMARCB1 mutations and harbor different driver events.

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.

Peripheral nerve sheath tumors of the breast.

Benign and malignant peripheral nerve sheath tumors can involve the breast, presenting as masses in the dermis, deep breast parenchyma or axillary soft tissue. Although the histologic features are frequently characteristic, diagnosis can be challenging on core needle biopsy, and the differential diagnosis includes a variety of other benign and malignant spindle cell lesions of the breast. Here, we review the key clinical and pathological features of breast schwannoma, neurofibroma, granular cell tumor, and malignant peripheral nerve sheath tumor.

Histopathologic evaluation of atypical neurofibromatous tumors and their transformation into malignant peripheral nerve sheath tumor in patients with neurofibromatosis 1-a consensus overview.

Patients with neurofibromatosis 1 (NF1) develop multiple neurofibromas, with 8% to 15% of patients experiencing malignant peripheral nerve sheath tumor (MPNST) during their lifetime. Prediction of transformation, typically from plexiform neurofibroma, is clinically and histologically challenging. In this overview, after a consensus meeting in October 2016, we outline the histopathologic features and molecular mechanisms involved in the malignant transformation of neurofibromas. Nuclear atypia alone is generally insignificant. However, with atypia, loss of neurofibroma architecture, high cellularity, and/or mitotic activity >1/50 but <3/10 high-power fields, the findings are worrisome for malignancy. We propose the term "atypical neurofibromatous neoplasms of uncertain biologic potential (ANNUBP)" for lesions displaying at least 2 of these features. This diagnosis should prompt additional sampling, clinical correlation, and possibly, expert pathology consultation. Currently, such tumors are diagnosed inconsistently as atypical neurofibroma or low-grade MPNST. Most MPNSTs arising from neurofibromas are high-grade sarcomas and pose little diagnostic difficulty, although rare nonnecrotic tumors with 3-9 mitoses/10 high-power fields can be recognized as low-grade variants. Although neurofibromas contain numerous S100 protein/SOX10-positive Schwann cells and CD34-positive fibroblasts, both components are reduced or absent in MPNST. Loss of p16/CDKN2A expression, elevated Ki67 labeling, and extensive nuclear p53 positivity are also features of MPNST that can to some degree already occur in atypical neurofibromatous neoplasms of uncertain biologic potential. Complete loss of trimethylated histone 3 lysine 27 expression is potentially more reliable, being immunohistochemically detectable in about half of MPNSTs. Correlated clinicopathological, radiologic, and genetic studies should increase our understanding of malignant transformation in neurofibromas, hopefully improving diagnosis and treatment soon.

Low-grade Schwann cell neoplasms with leptomeningeal dissemination: clinicopathologic and autopsy findings.

Leptomeningeal dissemination of low-grade Schwann cell neoplasms is an exceptionally rare occurrence and has not been well documented in the literature. We encountered 2 cases of leptomeningeal dissemination of low-grade Schwann cell neoplasms. Patient 1 was a 63-year-old woman with neurofibromatosis type 1 and a progressive low-grade malignant peripheral nerve sheath tumor developing from a diffuse/plexiform orbital neurofibroma that arose in childhood. The neoplasm demonstrated local and leptomeningeal dissemination intracranially leading to the patient's death. There was partial loss of H3K27 tri-methylation, p16 and collagen IV. Patient 2 was a 60-year-old man without neurofibromatosis type 1 who presented with cranial nerve symptoms and a disseminated neoplasm with a Schwann cell phenotype. The neoplasm stabilized after irradiation and chemotherapy, but the patient died of medical complications. Autopsy findings documented disseminated leptomeningeal disease in the intracranial and spinal compartment. H3K27M tri-methylation was preserved. The clinicopathologic and autopsy findings are studied and presented, and the literature is reviewed.

Loss of H3K27 tri-methylation is a diagnostic marker for malignant peripheral nerve sheath tumors and an indicator for an inferior survival.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas that can show overlapping features with benign neurofibromas as well as high-grade sarcomas. Additional diagnostic markers are needed to aid in this often challenging differential diagnosis. Recently mutations in two critical components of the polycomb repressor 2 (PRC2) complex, SUZ12 and EED, were reported to occur specifically in MPNSTs while such mutations are absent in neurofibromas, both in the setting of neurofibromatosis (NF) and sporadic cases. Furthermore, both SUZ12 and EED mutations in MPNSTs were associated with loss of H3K27 tri-methylation, a downstream target of PRC2. Therefore, we tested whether H3K27me3 immunohistochemistry is useful as a diagnostic and prognostic marker for MPNSTs. We performed H3K27me3 immunohistochemistry in 162 primary MPNSTs, 97 neurofibromas and 341 other tumors using tissue microarray. We observed loss of H3K27me3 in 34% (55/162) of all MPNSTs while expression was retained in all neurofibromas including atypical (n=8) and plexiform subtypes (n=24). Within other tumors we detected loss of H3K27me3 in only 7% (24/341). Surprisingly, 60% (9/15) of synovial sarcomas and 38% (3/8) of fibrosarcomatous dermatofibrosarcoma protuberans (DFSP) showed loss of H3K27 trimethylation. Only 1 out of 44 schwannomas showed loss of H3K27me3 and all 4 perineuriomas showed intact H3K27me3. Furthermore, MPNSTs with loss of H3K27 tri-methylation showed inferior survival compared with MPNSTs with intact H3K27 tri-methylation, which was validated in two independent cohorts. Our results indicate that H3K27me3 immunohistochemistry is useful as a diagnostic marker, in which loss of H3K27me3 favors MPNST above neurofibroma. However, H3K27me3 immunohistochemistry is not suitable to distinguish MPNST from its morphological mimicker synovial sarcoma or fibrosarcomatous DFSP. Since loss of H3K27 tri-methylation was related to poorer survival in MPNST, chromatin modification mediated by this specific histone seems to orchestrate more aggressive tumour biology.

[Diagnostic value of STAT6 immunohistochemistry in solitary fibrous tumor/meningeal hemangiopericytoma].

OBJECTIVE: To investigate the diagnostic role of STAT6 immunohistochemistry in solitary fibrous tumors (SFT)/meningeal hemangiopericytomas (HPC). METHOD: Evaluated the expression of STAT6, vimentin, CD34, EMA, PR, S-100, CD56, GFAP and Ki-67 in a cohort of 37 SFT/meningeal HPC, 30 meningiomas and 30 schwannomas by immunohistochemistry staining. RESULTS: All SFT/meningeal HPC demonstrated nuclear positivity for STAT6, and the proportion of positive tumor cells ranged from 60% to 95%, with no significant difference cases.Vimentin was strongly positive in all cases. CD34, EMA and PR positivity was found in 32 cases, 1 case and 4 cases, respectively.S-100 protein, CD56 and GFAP were negative; Ki-67 labeling index was 1%-8%. However, the meningiomas and schwannomas were negative for STAT6. CONCLUSIONS: STAT6 is a relatively specific biomarker for SFT/meningeal HPC, and may be used in the diagnosis and differential diagnosis of SFT/meningeal HPC, especially for the atypical cases, and allows the precise pathologic diagnosis of SFT/meningeal HPC.

Hybrid Epithelioid Schwannoma/Perineurioma.

We report a case of a 58-year-old who woman presented with a solitary slowly growing subcutaneous nodule covered by normally appearing skin on her left groin. Microscopically, the lesion was well circumscribed but unencapsulated, and showed biphasic cellular differentiation. One cell population was presented by small rounded (epithelioid) cells arranged singly, in small aggregates or short cords, whereas the second one was composed of cells with slender nuclei and delicate elongated bipolar cytoplasmic processes. On immunohistochemistry, the epithelioid component showed positive reaction for S-100 protein and negative for epithelial membrane antigen (EMA), thus compatible with schwannian differentiation and resembling epithelioid schwannoma. The other component showed a reverse immunophenotype being S-100 protein negative and EMA positive, thus corresponding to perineuriomatous differentiation. The clinicopathologic and immunohistochemical features of the lesion were compatible with hybrid epithelioid schwannoma/perineurioma, a rare morphological variant of peripheral nerve sheath tumors.

Epithelioid Schwannomas: An Analysis of 58 Cases Including Atypical Variants.

The histologic features and outcome of 58 cases of epithelioid schwannoma were studied to determine the significance of atypical histologic features. Cases were retrieved from personal consultation files from 1999 to 2013. Patients (31 male and 26 female patients) ranged in age from 14 to 80 years (median, 38 y). Two patients had schwannomatosis 1. Tumors developed in the dermis/subcutis (n=56) or muscle (n=2) of the upper extremity (34.5%), lower extremity (34.5%), thorax/abdomen/back (18%), and less common anatomic locations including the scalp, neck, lip, and breast. They ranged in size from 0.25 to 4.5 cm (median, 2.0 cm). Typically circumscribed and surrounded by a perineurium, they comprised single or small groups of epithelioid schwann cells with a moderate amphophilic cytoplasm and occasional nuclear pseudoinclusions. Stroma varied from myxoid to hyalinized, often with thick-walled vessels (55 cases). Mitotic rate ranged from 0 to 9 mitoses/10 high-power field (HPF) (2.37 mm) in the most active areas (mean, 2 to 3 mitoses/10 HPFs). Thirteen cases (22%) were "atypical," defined by a high mitotic rate (≥3 mitoses per 10 HPFs) and nuclear size variation (≥3:1). All (56/56) expressed S100 protein; type IV collagen invested groups or individual cells (16/17). Melanoma markers were negative, except for melan A (1 case). Follow-up in 39 patients (median, 78 mo; range, 6 to 174 mo) indicated that 31 (79%) were alive without disease (including 9/13 atypical cases; median, 78 mo), 7 (18%) were alive with unknown status, and 1 patient had died of unrelated causes. One tumor recurred, but none metastasized. Epithelioid schwannomas, even those with atypical features, are benign and do not constitute a histologic continuum with epithelioid malignant peripheral nerve sheath tumors, which typically occur in deep soft tissues and have more anaplastic features.

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.