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.

Recurrence of adult granulosa cell tumor of the ovary: experience at a tertiary care center.

Adult granulosa cell tumor (AGCT) is the most common ovarian sex cord stromal tumor with a favorable prognosis. However, a subset of patients develop recurrence. We retrieved and reviewed 156 cases of AGCT reported between 1992 and 2012. The ages ranged from 20 to 84 years (mean, 48 years). The size of the tumor ranged from 0.8 to 25 cm (mean, 10 cm). Histologically, all tumors were composed of round or polygonal cells with indented or grooved nuclei, eosinophilic cytoplasm, and well defined cell borders. A diffuse pattern was seen in the majority followed by microfollicular, trabecular and macrofollicular. The mitotic figures ranged from 2 to a maximum of 21/10 HPFs. Focal necrosis were seen in 17 cases. Associated simple hyperplasia of endometrium was seen in 9 cases, complex hyperplasia in 2, and endometrioid adenocarcinoma of the endometrium in 3 cases. Recurrence was seen in 8 cases with a follow-up of 2 to 19 years (mean, 6 years). The recurrent tumors were mostly >5 cm and sites included the same adnexal site and contralateral ovary, omentum, mesentery of small bowel, abdominal wall, uterine and fallopian tube serosa, lymph nodes, pelvis, and appendix. Histologically, recurrent tumors exhibited a diffuse histologic pattern and a mitotic count of 6.8 as compared to 3.3 in primary tumors. In conclusion, a tumor size of >5 cm and a diffuse histologic pattern were associated with increased recurrence risk. The recurrent tumors hadz increased mitotic figures compared with primary tumors. Appendix, a very rare site of recurrence was seen in one of our cases.

Solid pseudopapilllary neoplasm of the pancreas. A clinicopathologic study of 25 cases from Pakistan and review of Literature.

Our aim was to describe the clinicopathologic features of cases of solid pseudopapillary neoplasm (SPN) of the pancreas diagnosed in our section. We retrieved hematoxylin and eosin and immunohistochemistry slides of SPN of pancreas diagnosed between 2002 and 2014 and reviewed slides. A total of 25 cases were included in the study. All were females. Age ranged from 12 to 45 years with mean age of 24 years. Tail of pancreas was the commonest location (40%). Tumor size ranged from 2.5 to 20 cm (mean tumor size, 9.5 cm). Distal pancreatectomy and pancreaticoduodenectomy were the commonest types of surgical resections performed. Most cases were confined to the pancreas. However, 2 cases extended beyond the pancreas, and an additional case metastasized to the omentum and liver. Pseudopapillary architecture and hyaline globules were the commonest histologic features, seen in 100% and 84% of cases, respectively. Vimentin, cluster of differentiation 10, cluster of differentiation 56, and neuron-specific enolase were the most useful immunohistochemical stains. Of those cases, in which follow-up was available, almost all (except 1) patients were alive and well even several years after resection. In conclusion, SPN is a rare tumor in our practice. As in international studies, our study also showed predilection for young females and excellent prognosis after surgical resection.

Malignant melanoma of anorectal region: a clinicopathologic study of 61 cases.

Anorectal malignant melanomas (AMMs) are aggressive neoplasms, which account for less than 1% of all anorectal tumors. Anorectal malignant melanomas are notorious for their diversity of histologic features and mimic a number of other tumors. Aberrant expression of immunohistochemical stains such as cytokeratins and CD117 (c-kit) further increases the risk of misdiagnosis. Aim of our study was to describe the common as well as unusual architectural and cytologic features that create difficulty in diagnosis. We also discussed the role of immunohistochemical stains in diagnosis of AMMs. We retrieved and reviewed 61 cases of anal melanoma diagnosed in our institution between January 2005 and May 2014. Epithelioid cell type was observed in 57 (93.4%) cases, spindle cells in 35 (57.4%) cases, pleomorphic in 12 (19.7%) cases, and lymphoma-like in 2 (3.3%) cases. Cytoplasmic clearing was observed in 16.4% and nuclear pseudoinclusions in 9.8% cases. Twenty-one point three percent cases were completely amelanotic, and 36.1% showed focal melanin pigment. Average mitotic count was 2 mitoses/high-power fields. Nesting pattern was seen in 24.6%, pseudoalveolar pattern in 11.5%, and peritheliomatous/pseudopapillary pattern in 5% cases. Positive expression of vimentin, S-100, HMB-45, and Melan A was seen in 100%, 100%, 94.4%, and 93.3% cases, respectively. Cytokeratins were positive in 9% and CD117 (c-kit) in 20% of cases in which they were performed. In conclusion, AMMs should be considered in the differential of any malignant tumor of anorectal region without obvious glandular and squamoid differentiation. The knowledge of amelanotic nature, unusual histologic features, and aberrant immunohistochemical expression is helpful in avoiding misdiagnosis.

Assessing Morphological Diversity of Acinic Cell Carcinoma of Salivary Glands at a Tertiary Care Hospital in Pakistan.

INTRODUCTION: Acinic cell carcinoma (AciCC) is a rare clinical entity and a salivary gland malignancy. It is associated with wide histological variations in the cytomorphological patterns. METHODS: Sixty cases diagnosed as AciCC from 2002 to 2023 were assessed for diverse cytomorphological patterns. RESULTS: The mean age of patients at the time of diagnosis was 44.35±16.8 years ranging from 15 to 81 years. Females comprised 58.3% for a F: M ratio of 1.4:1. Fifty three cases (88.3%) occurred in the parotid gland, two cases in the nasal region (3.3%), and one case each in the soft plate and upper lip (1.7%). The location of the remaining three cases was not specified. The most common presenting complaint was a well-defined facial swelling associated with pain. The average tumor size was 3.8±1.9 cm. The most predominant architectural pattern was solid (83.3%) followed by microcystic (60%), then follicular (41.7%), papillary cystic (14.3%), and tubulocystic (28.6%), and AciCC with de-differentiation/high-grade transformation was reported in three cases (5%). In 83.3% of the cases (50 out of 60), we noticed a mixture of two or more growth patterns. Other degenerative changes included prominent lymphoid stroma, hemorrhage, and cystic change. CONCLUSION: Awareness and recognition of diverse cytomorphological patterns of AciCC, especially in institutions of a developing country where there is limited availability of highly specific and sensitive immunohistochemical stains or molecular diagnostics, are crucial and essential.

Role of SOX10 Immunohistochemical Expression in Diagnosing Triple Negative Breast Cancer and Its Correlation With Clinicopathological Features.

BACKGROUND: Triple-negative breast cancer (TNBC) poses a diagnostic challenge for histopathologists due to the reduced frequency of breast-specific markers. SOX10 has emerged as a useful diagnostic marker for TNBC. The aim of our study was to determine the frequency of SOX-10 immunohistochemical (IHC) expression in our cohort and assess its correlation with clinicopathological and histological features. MATERIALS AND METHODS: We included 72 primary TNBC cases. Specimens included tru-cut biopsies and excision specimens. We stained whole slide sections of these specimens with SOX10 antibody and calculated its frequency (%) of expression and H-score. We applied the chi-square test to assess the correlation between SOX10 expression and clinicopathological and histological features such as the patient's age, specimen type, tumor size, histological type, histological grade, nuclear pleomorphism, mitotic count, tumor-infiltrating lymphocytes (TILs), necrosis, calcification, lymphovascular invasion (LVI), lymph node involvement, T stage, and N stage. RESULTS: SOX10 expression was observed in 42 (58.3%) cases with a median H-score of 57.5. The expression was significantly higher in tru-cut biopsy specimens as compared to excision specimens (73.5 vs 41.7%) and TILs negative tumors as compared to TILs positive tumors (64.3% vs 27.3). Metaplastic carcinoma showed reduced expression when compared with non-metaplastic tumors (35.7% vs 63.8%), but statistical significance was not achieved. No correlation was observed with the patient's age, tumor size, histological type, histological grade, nuclear pleomorphism, mitotic count, necrosis, calcification, LVI, lymph node involvement, T stage, and N stage. CONCLUSION: SOX10 was expressed in more than half of the TNBC cases of our study which not only highlights its diagnostic utility but advocated its application in combination with other breast-specific markers. The expression didn't correlate with the majority of clinicopathological and histological features, but correlation with tru-cut biopsy specimens and absence of TILs draws attention towards possible roles of proper fixation and host immunity, respectively.

Events in CNS Tumor Pathology Post-2016 WHO CNS: cIMPACT-NOW Updates and Other Advancements: A Comprehensive Review Plus a Summary of the Salient Features of 2021 WHO CNS 5.

Introduction: The 2016 World Health Organization Classification (WHO) of Tumors of the Central Nervous System (CNS) represented a major change. It recommended an "integrated diagnosis" comprising histologic and molecular information facilitating a more precise diagnosis of specific CNS tumors. Its goal was to provide greater diagnostic precision and reproducibility resulting in more clinical relevance and predictive value, ultimately leading to better patient care. Advances in molecular classification, mostly resulting from DNA methylation array profiling of CNS tumors, were occurring at a very rapid pace and required more rapid integration into clinical practice. Methods: cIMPACT-NOW updates and other recent papers plus salient features of 2021 WHO CNS5 in this comprehensive write-up were reviewed. Results: CNS tumor classification needs to be updated at a rapid pace and mechanisms put into place to guide diagnosticians and clinicians in the interim period if major changes in the classification of tumor types came to light. Recognizing the need to integrate these into clinical practice more rapidly and without inordinate delay, the International Society of Neuropathology (ISN) 2016 sponsored an initiative called cIMPACT-NOW. Discussion and/or Conclusion: Goal of cIMPACT-NOW was to provide clarification regarding contentious issues arising in the wake of the 2016 WHO CNS update as well as report new advancements in molecular classification of CNS tumors and new tumor entities emerging as a result of these advancements. cIMPACT-NOW updates: It thus laid the foundation for the 5th edition of the WHO Classification of CNS tumors (2021 WHO CNS 5). We have discussed cIMPACT updates in detail in this review. In addition, molecular diagnostics including DNA methylation-based classification of CNS tumors and the practical use of molecular classification in the prognostication and treatment of CNS tumors is discussed. Finally, the salient features of the new CNS tumor classification are summarized.

Anaplastic Large-cell Lymphoma Involving Gastrointestinal Tract: A Clinicopathologic Study of 25 Cases of a Rare Tumor at a Rare Site.

Background. Anaplastic large-cell lymphoma (ALCL) is an uncommon lymphoma divided into anaplastic lymphoma kinase (ALK) positive, ALK negative, and breast implant-associated (BIA) ALCL. Gastrointestinal tract involvement is very rare and may be difficult to diagnose. Its recognition is crucial as prognostic ramifications are different. Objectives. To describe clinicopathological features of ALCL involving the gastrointestinal tract. Materials and Methods. Slides were reviewed. Diagnosis was confirmed. Histological and immunohistochemical features were described. Results.Twenty-five tumors were diagnosed during the study period. Ages ranged from 14 to 65 years (mean 41 years). Mean age for ALK-negative and ALK-positive patients were 49 and 17 years, respectively. Twenty-one were males and 4 were females. Eighteen involved small intestine. Mean tumor size was 4.2 cm. All showed diffuse sheets of large anaplastic cells with pleomorphic nuclei, abundant pink cytoplasm, and strong positivity for CD30. Epithelial membrane antigen was positive in 17 tumors and keratin was negative in all. Eighteen tumors were ALK negative. Out of 14 patients with follow-up, 12 died within a few months of diagnosis. Seven had stage IE, 5 had stage IIE, and 2 had stage IV disease. Two patients were alive at 35 and 60 months. Twelve received chemotherapy. Conclusion. A marked male predominance was noted. Small intestine was the commonest site of involvement. Majority were ALK negative. ALK-negative tumors occurred in older patients and ALK positive in younger patients. Prognosis was poor. ALCL should be included in the differential diagnosis of anaplastic epithelioid cell neoplasms in the gastrointestinal tract.

Clinicopathological features of dysembryoplastic neuroepithelial tumor: a case series.

BACKGROUND: Dysembryoplastic neuroepithelial tumors are rare benign supratentotrial epilepsy-associated glioneuronal tumors of children and young adults. Patients have a long history of seizures. Proper surgical resection achieves long term seizure control. We describe the clinicopathological features of dysembryoplastic neuroepithelial tumor cases reported in our practice and review the published literature. METHODS: All cases of Pakistani ethnicity were diagnosed between 2015 and 2021 were included. Slides were reviewed and clinicopathological features were recorded. Follow-up was obtained. Extensive literature review was conducted. RESULTS: Fourteen cases were reported. There were 12 males and 2 females. Age range was 9-45 years (mean 19 years). Majority were located in the temporal and frontal lobes. Duration of seizures prior to resection ranged from 2 months to 9 years with mean and median duration of 3.2 and 3 years, respectively. Histologically, all cases demonstrated a multinodular pattern, specific glioneuronal component, and floating neurons. Simple and complex forms comprised seven cases each. No significant nuclear atypia, mitotic activity, or necrosis was seen. Ki-67 proliferative index was very low. Cortical dysplasia was noted in adjacent glial tissue in four cases. Follow-up ranged from 20 to 94 months. Seizures continued following resection in all but one case but were reduced in frequency and intensity. In one case, seizures stopped completely following surgery. CONCLUSION: Clinicopathological features were similar to those in published literature. However, a marked male predominance was noted in our series. Seizures continued following resection in all but one case but were reduced in frequency and intensity. This series will help raise awareness among clinicians and pathologists in our part of the world about this seizure-associated tumor of children and young adults.

Comprehensive Molecular Profiling of Sinonasal Teratocarcinosarcoma Highlights Recurrent SMARCA4 Inactivation and CTNNB1 Mutations.

Sinonasal teratocarcinosarcoma (TCS) is a rare tumor defined by intermixed neuroepithelial, mesenchymal, and epithelial elements. While its etiology was historically ambiguous, we recently reported frequent SMARCA4 loss by immunohistochemistry, suggesting that TCS might be related to SMARCA4-deficient sinonasal carcinomas. However, other molecular alterations including CTNNB1 mutation have been reported in TCS, and its full genetic underpinnings are unclear. Here, we performed the first comprehensive molecular analysis of sinonasal TCS to better understand its pathogenesis and classification. We collected 30 TCS including 22 cases from our initial study. Immunohistochemical loss of SMARCA4 was seen in 22 cases (73%), with total loss in 18 cases (60%). ß-catenin showed nuclear localization in 14 cases (64%) of the subset tested. We selected 17 TCS for next-generation sequencing with enrichment for partial or intact SMARCA4 immunoexpression. We identified inactivating SMARCA4 mutations in 11 cases (65%) and activating CTNNB1 mutations in 6 cases (35%), including 5 cases with both. Of 5 cases that lacked SMARCA4 or CTNNB1 mutation, 2 harbored other SWI/SNF complex and Wnt pathway alterations, including 1 with SMARCB1 inactivation and 1 with concomitant APC and ARID1A mutations, and 3 had other findings, including DICER1 hotspot mutation. These findings confirm that SMARCA4 inactivation is the dominant genetic event in sinonasal TCS with frequent simultaneous CTNNB1 mutations. They further underscore a possible relationship between TCS and sinonasal carcinomas with neuroendocrine/neuroectodermal differentiation. However, while SMARCA4 and ß-catenin immunohistochemistry may help confirm a challenging diagnosis, TCS should not be regarded as a molecularly defined entity.

Intracranial mesenchymal tumors with FET-CREB fusion are composed of at least two epigenetic subgroups distinct from meningioma and extracranial sarcomas.

'Intracranial mesenchymal tumor, FET-CREB fusion-positive' occurs primarily in children and young adults and has previously been termed intracranial angiomatoid fibrous histiocytoma (AFH) or intracranial myxoid mesenchymal tumor (IMMT). Here we performed genome-wide DNA methylation array profiling of 20 primary intracranial mesenchymal tumors with FET-CREB fusion to further study their ontology. These tumors resolved into two distinct epigenetic subgroups that were both divergent from all other analyzed intracranial neoplasms and soft tissue sarcomas, including meningioma, clear cell sarcoma of soft tissue (CCS), and AFH of extracranial soft tissue. The first subgroup (Group A, 16 tumors) clustered nearest to but independent of solitary fibrous tumor and AFH of extracranial soft tissue, whereas the second epigenetic subgroup (Group B, 4 tumors) clustered nearest to but independent of CCS and also lacked expression of melanocytic markers (HMB45, Melan A, or MITF) characteristic of CCS. Group A tumors most often occurred in adolescence or early adulthood, arose throughout the neuroaxis, and contained mostly EWSR1-ATF1 and EWSR1-CREB1 fusions. Group B tumors arose most often in early childhood, were located along the cerebral convexities or spinal cord, and demonstrated an enrichment for tumors with CREM as the fusion partner (either EWSR1-CREM or FUS-CREM). Group A tumors more often demonstrated stellate/spindle cell morphology and hemangioma-like vasculature, whereas Group B tumors more often demonstrated round cell or epithelioid/rhabdoid morphology without hemangioma-like vasculature, although robust comparison of these clinical and histologic features requires future study. Patients with Group B tumors had inferior progression-free survival relative to Group A tumors (median 4.5 vs. 49 months, p = 0.001). Together, these findings confirm that intracranial AFH-like neoplasms and IMMT represent histologic variants of a single tumor type ('intracranial mesenchymal tumor, FET-CREB fusion-positive') that is distinct from meningioma and extracranial sarcomas. Additionally, epigenomic evaluation may provide important prognostic subtyping for this unique tumor entity.