TFG::MET-rearranged soft tissue tumor: A rare infantile neoplasm with a distinct low-grade triphasic morphology.

This article presents 2 cases of TFG::MET-rearranged mesenchymal tumor, an extremely rare molecular subset among an emerging group of mesenchymal neoplasms with kinase gene (NTRK, BRAF, RET and others) alterations. Both tumors were congenital, occurred in female patients and presented as huge masses on the trunk and thigh, measuring 18 and 20 cm in the largest dimension. Both cases showed identical areas with a distinctive triphasic morphology resembling fibrous hamartoma of infancy (FHI), consisting of haphazardly arranged ovoid to spindled cells traversed by variably cellular and hyalinized fascicles admixed with (most likely non-neoplastic) adipose tissue. In other areas, a high-grade infantile fibrosarcoma/malignant peripheral nerve sheath tumor-like (IFS/MPNST-like) morphology was present in both cases. While the first case co-expressed CD34 and S100 protein, the other case did not. When combined with the three previously reported MET-rearranged cases (of which two harbored TFG::MET fusion), 3/5 and 3/4 of MET-rearranged and TFG::MET fusion-associated tumors, respectively exhibited similar triphasic FHI-like low-grade morphology. This points toward the existence of a relatively distinct morphological subset among kinase-fusion-associated tumors which seems to be strongly associated with MET fusions. It seems some of these low-grade cases may transform into a high-grade variant with IFS/MPNST-like morphology as has been observed in other tumors with kinase gene fusions. While most cases seem to follow an indolent clinical course, the recognition of these tumors is clinically relevant as MET tyrosine kinase inhibitors might represent an effective treatment option for clinically aggressive or unresectable cases.

Amplification of the PLAG-family genes-PLAGL1 and PLAGL2-is a key feature of the novel tumor type CNS embryonal tumor with PLAGL amplification.

Pediatric central nervous system (CNS) tumors represent the most common cause of cancer-related death in children aged 0-14 years. They differ from their adult counterparts, showing extensive clinical and molecular heterogeneity as well as a challenging histopathological spectrum that often impairs accurate diagnosis. Here, we use DNA methylation-based CNS tumor classification in combination with copy number, RNA-seq, and ChIP-seq analysis to characterize a newly identified CNS tumor type. In addition, we report histology, patient characteristics, and survival data in this tumor type. We describe a biologically distinct pediatric CNS tumor type (n = 31 cases) that is characterized by focal high-level amplification and resultant overexpression of either PLAGL1 or PLAGL2, and an absence of recurrent genetic alterations characteristic of other pediatric CNS tumor types. Both genes act as transcription factors for a regulatory subset of imprinted genes (IGs), components of the Wnt/ß-Catenin pathway, and the potential drug targets RET and CYP2W1, which are also specifically overexpressed in this tumor type. A derived PLAGL-specific gene expression signature indicates dysregulation of imprinting control and differentiation/development. These tumors occurred throughout the neuroaxis including the cerebral hemispheres, cerebellum, and brainstem, and were predominantly composed of primitive embryonal-like cells lacking robust expression of markers of glial or neuronal differentiation (e.g., GFAP, OLIG2, and synaptophysin). Tumors with PLAGL1 amplification were typically diagnosed during adolescence (median age 10.5 years), whereas those with PLAGL2 amplification were diagnosed during early childhood (median age 2 years). The 10-year overall survival was 66% for PLAGL1-amplified tumors, 25% for PLAGL2-amplified tumors, 18% for male patients, and 82% for female patients. In summary, we describe a new type of biologically distinct CNS tumor characterized by PLAGL1/2 amplification that occurs predominantly in infants and toddlers (PLAGL2) or adolescents (PLAGL1) which we consider best classified as a CNS embryonal tumor and which is associated with intermediate survival. The cell of origin and optimal treatment strategies remain to be defined.

Metastatic renal cell carcinoma to pancreas and gastrointestinal tract: a clinicopathological study of 3 cases and review of literature.

BACKGROUND: Renal Cell Carcinoma (RCC) metastasizes in approximately 20-30% cases. The most common sites for metastases are the lungs, bones, liver, and brain. Metastases of RCC in the gastrointestinal tract (GIT) are very rare. Metastatic RCC has a poor prognosis. We herein present a case series of three patients with metastatic disease in the colon, duodenum, and pancreas following complete resection of RCC. METHODS: Hematoxylin and Eosin and immunohistochemical slides of 3 cases of RCC metastatic to GIT were reviewed. These cases were diagnosed between 2002 and 2019 at French Medical Institute for Mothers and Children (FMIC), Kabul, Afghanistan, and Aga Khan University Hospital (AKUH), Karachi, Pakistan. We also present a detailed review of published literature. RESULTS: We reviewed cases of three patients, two females and one male, with a mean age of 57.3 years (range 40-67 years) who underwent nephrectomy for RCC. They developed metastases in the colon, pancreas, and duodenum, respectively 12-168 months (median time 156 months) following primary tumor resection. The patient with metastatic RCC in colon presented with abdominal pain and constipation. An ulcerated mass was found on colonoscopy 30 cm from the anal verge. Diagnosis of RCC with rhabdoid features was confirmed in both primary and metastatic tumors. The second patient developed a metastatic nodule in the head of pancreatic while the third patient developed metastatic nodules in the duodenum and pancreas which were detected by Computed Tomography (CT) scanning. Histopathological examination confirmed the presence of clear cell RCC in the metastatic nodules in both cases. CONCLUSION: Metastatic RCC should be considered in the differential diagnosis of mass in the gastrointestinal (including pancreaticobiliary) tract especially in presence of a past history of RCC. These patients should be screened thoroughly by physical examination and appropriate imaging studies.

Synchronous Well-differentiated Endometrioid Adenocarcinoma and Leiomyosarcoma of the Uterus With Pulmonary Metastasis in a 50-Yr-Old Woman: A Case Report and Review of Literature.

The most common synchronous gynecologic malignancies are endometrial and ovarian cancers. However, synchronous endometrial adenocarcinoma and uterine leiomyosarcoma are extremely rare. We report the case of a 50-yr-old woman who was diagnosed with concomitant endometrial adenocarcinoma and uterine leiomyosarcoma. The sarcomatous neoplasm was positive for anti-smooth muscle actin and CD10, and focally positive for Cytokeratin AE1/AE3 and Cytokeratin Cam 5.2. She underwent total abdominal hysterectomy with bilateral salpingoopherectomy followed by radiation, brachytherapy, and chemotherapy. Three years later, she presented with cough and dyspnea and was found to have pulmonary metastasis. These tumor cells were positive for anti-smooth muscle actin, Cytokeratin AE1/AE3, Cytokeratin Cam 5.2, and epithelial membrane antigen, and therefore a diagnosis of lung metastasis from myometrial leiomyosarcoma was made. She received chemotherapy postoperatively. Currently, the patient has multiple lung metastases, is on Megestrol Acetate and is clinically well. This is the first reported case of concomitant uterine malignancies with pulmonary metastases and a long follow-up of 9 yr. It is important to rule out carcinosarcoma as a differential diagnosis in such patients.

Atypical lipomatous tumour/well-differentiated liposarcoma and de-differentiated liposarcoma in patients aged ≤ 40 years: a study of 116 patients.

AIMS: Limited data exist on atypical lipomatous tumour (ALT)/well-differentiated liposarcoma (WDL) and de-differentiated liposarcoma (DDLPS) in children and young adults. METHODS AND RESULTS: Cases of ALT/WDL/DDLPS arising in patients aged ≤ 40 years were collected from multiple institutional and consultation archives. A total of 116 cases of ALT/WDL (75) and DDLPS (41) were identified, representing fewer than 5% of these tumours seen at our institutions during this time-period. The patients (59 male/57 female) ranged in age from 8 to 40 years. Sites included deep central (abdomen/retroperitoneum/pelvis/groin) (n = 60), extremity (n = 42), trunk (n = 5), head/neck (n = 8) and mediastinum (n = 1). De-differentiated patterns included: high-grade pleomorphic sarcoma, myxofibrosarcoma-like, heterologous rhabdomyoblastic differentiation, low-grade spindle cell sarcoma and homologous lipoblastic differentiation. Forty-one patients experienced a local recurrence and 11 patients with DDLPS developed metastasis. ALT arising in the extremities had lower recurrence rates than deep central WDL (5-year recurrence-free survival 88.9% versus 59.0%; P = 0.002), while patients with deep central DDLPS experienced significantly more adverse events compared to WDL at this site (5-year event-free survival 11.9% versus 59.0%) (P < 0.0001). Seven (of eight) head/neck tumours had follow-up available; five recurred, and one patient (DDLPS) with recurrence also experienced a metastasis. The single mediastinal tumour (DDLPS) recurred and metastasised. CONCLUSION: ALT/WDL and DDLPS occurring in patients aged ≤ 40 years is rare, but exhibits similar morphological features to its counterparts in older adults, including potential for heterologous and homologous de-differentiation in the latter. Although case numbers are limited, tumours arising in the head and neck exhibit high rates of adverse events, suggesting that classification as WDL rather than ALT is more appropriate.

Hybrid peripheral nerve sheath tumors: report of five cases and detailed review of literature.

BACKGROUND: Hybrid peripheral nerve sheath tumors (PNSTs) have been recognized recently and were first included in the 4th edition of World Health Organization (WHO) Classification of Tumors of Soft tissue and Bone, published in 2013. These tumors show combined features of more than one type of conventional benign peripheral nerve sheath tumors. The most common combinations are those of schwannoma/perineurioma followed by combinations of neurofibroma/schwannoma and neurofibroma/perineurioma. A detailed literature review of published cases is presented. We have discussed the types and etiology, epidemiology and sites of localization, gross and microscopic appearances and immunohistochemical features of hybrid PNSTs and association of these tumors with tumor syndromes. CASE PRESENTATION: We have included five cases which were diagnosed in our department as we believe that publication of these new cases is relevant for the improved understanding of these specific tumors. Four of our five patients were males, mean age was 24 years. There was wide variation in the location of these tumors. Mean size of excised tumors was 5.5 cms in the greatest dimensions. Three out of five cases represented hybrid schwannoma/perineurioma histologically. No significant nuclear atypia, mitotic activity or necrosis seen. All five cases were completely excised. All five patients are alive and well at the time of writing with no recurrence. CONCLUSION: Hybrid PNSTs are distinct tumors and are usually benign. However, rare case reports have described local recurrence and at least two recent case reports have described malignant transformation in these tumors. Further studies on large number of cases are required to determine the exact pathogenetic basis of these tumors.

Schwannomas with pseudoglandular elements: clinicopathologic study of 61 cases.

Schwannomas are benign neoplasms of peripheral nerve sheath. A number of morphologic variants of schwannoma have been described. The pseudoglandular variant is very rare. We retrieved and reviewed hematoxylin and eosin slides of all cases of schwannoma reported between 2007 and 2014 to look for pseudoglandular elements. Pseudoglandular cystic spaces were seen in 61 (6.3%) of 971 schwannomas diagnosed during the study period. Of these 61 cases, 56 (91.8%) were located in the spinal nerve roots. The majority (60.6%) were male. Mean age in these 61 cases was 41 years. Mean tumor size was 3.5 cm. All 61 cases showed typical Antoni A and Antoni B areas with multiple pseudoglandular cystic spaces scattered throughout. These areas were lined by flat to cuboidal cells which showed positivity for immunohistochemical stain S-100 and were negative for epithelial membrane antigen. An average of 7 pseudoglandular cystic spaces was noted per case. In conclusion, pseudoglandular cystic spaces are lined by Schwann cells and most likely represent degenerative changes in schwannoma probably degenerated Verocay bodies. They are rare albeit well-defined features seen in a significant though small number of schwannomas. It is important not to mistake them for other neoplasms. Larger studies are required to determine predilection of these changes in spinal nerve root schwannomas as seen in our series.

Congenital (infantile) fibrosarcoma of the scalp: a case series and review of literature.

INTRODUCTION: Congenital infantile fibrosarcoma (CIFS) is a soft tissue sarcoma of infants mainly involving lower extremities usually presenting during the first year of life. A subset of cases occur in the head and neck, but scalp involvement is exceptionally rare. PATIENTS AND METHODS: We report clinicopathological features of three cases of CIFS involving the scalp diagnosed between 2011 and 2012. RESULTS: The ages of the three patients at the time of diagnosis ranged from 12 to 90 days (mean 48 days). All were males and presented with scalp swelling at birth which grew rapidly in size. The tumor was located in the left temporal region in two cases and the right temporoparietal region in one case. On imaging, underlying bone involvement was noted in two cases. The mean size of the resected tumors was 8 cm. All cases exhibited a cellular tumor arranged in sheets of uniform oval to spindle cells, increased mitosis, and hemangiopericytoma-like vessels. All patients are alive after a mean follow-up of 39.6 months. Recurrence was seen in one case due to incomplete excision. No metastasis was seen in any of the cases. CONCLUSION: CIFS of the scalp is rare and carries a good prognosis. Underlying bone erosion is rare but was noted seen in two of our cases. A male predominance was seen in our cases.

Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin.

Polymorphous low-grade adenocarcinoma (PLGA) and cribriform adenocarcinoma of minor salivary gland (CAMSG) are low-grade carcinomas arising most often in oral cavity and oropharynx, respectively. Controversy exists as to whether these tumors represent separate entities or variants of one spectrum, as they appear to have significant overlap, but also clinicopathologic differences. As many salivary carcinomas harbor recurrent translocations, paired-end RNA sequencing and FusionSeq data analysis was applied for novel fusion discovery on two CAMSGs and two PLGAs. Validated rearrangements were then screened by fluorescence in situ hybridization (FISH) in 60 cases. Histologic classification was performed without knowledge of fusion status and included: 21 CAMSG, 18 classic PLGA, and 21 with "mixed/indeterminate" features. The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions, respectively, while no fusion candidates were identified in two PLGAs. FISH for PRKD1 rearrangements identified 11 additional cases (22%), two more showing ARID1A-PRKD1 fusions. As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol and protein kinase C signal transduction pathway, we expanded the investigation for these genes by FISH. Six additional cases each showed PRKD2 and PRKD3 rearrangements. Of the 26 (43%) fusion-positive tumors, there were 16 (80%) CAMSGs and 9 (45%) indeterminate cases. A PRKD2 rearrangement was detected in one PLGA (6%). We describe novel and recurrent gene rearrangements in PRKD1-3 primarily in CAMSG, suggesting a possible pathogenetic dichotomy from "classic" PLGA. However, the presence of similar genetic findings in half of the indeterminate cases and a single PLGA suggests a possible shared pathogenesis for these tumor types.