Desmoplastic Small Cell Tumor Research Articles

Abstract 130: Multi-omic analysis of desmoplastic small sound cell tumors reveal distinct epithelial and neuroendocrine lineages

Abstract Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive sarcoma subtype that is usually uncurable. All malignant cells harbor a pathognomonic EWSR1::WT1 fusion protein (FP), but FP-targeted agents are nonexistent, and less than 20% of patients survive beyond five years. Lacking the availability of FP-targeted drugs, we seek to understand how the FP regulates tumor cells to promote the characteristic multilineage phenotypes of epithelial and neuroendocrine (NE) cell fates to discover a therapeutic opportunity. Herein, we share the results of gene expression and chromatin accessibility analyses to explore fundamental mechanisms explaining epithelial and NE biology in DSRCT. We profiled 85,640 nuclei from fresh-frozen tissue of nine DSRCT patients post-chemotherapy using single-nucleus RNA-sequencing (snRNA-seq) and ATAC-sequencing (snATAC-seq). A subset of DSRCT patients with low or negative expression of AR expressed partial NE reprogramming, akin to NE prostate cancer (NEPC), exhibiting NE markers (SYP, ENO2, CHG, FOXA2, ASCL1, and SOX2). Another patient subset expressed epithelial markers (MUC1, MUC6, KRT18, KRT23, CDH1). One specimen appeared to exhibit both markers - implying a hybrid or a poorly differentiated phenotype. This suggests that DSRCT could be classified into three subtypes: 1) Epithelial/AR-positive, 2) NE-positive, and 3) hybrid AR/NE. We used CytoTRACE to predict differentiation states. As expected, normal cells (i.e., fibroblasts and immune cells) were the most differentiated. Neoplastic cells, identified by EWSR1::WT1 gene targets and copy number variations, had lower differentiation scores, indicative of a less differentiated phenotype. The NE subtype had the lowest differentiation score indicative of open chromatin and greater plastic capacity, previously implicated in NEPC. SnATAC-seq revealed that the WT1 motif was enriched in malignant cells. Epithelial/AR-positive subtypes were enriched in DNA-response elements for nuclear receptors (ARE, GRE, and PGR) and the forkhead box family of transcription factors (FOXA1, a known pioneer factor for AR). The NE subtype lacked the ARE, GRE, and PGR motifs but was enriched with FOXA1 and neural-specific motifs, including NEUROD1, ATOH1, OLIG2, and NANOG.We show significant heterogeneity in DSRCT phenotypes, where we observe both epithelial and NE lineages. Initially, we detected the Epithelial/AR-positive and NE-positive lineages by gene expression, but the snATAC-seq data also supports this. Although the emergence of the NE subtype in prostate cancer is generally in response to therapy, how it emerges in DSRCT is yet unknown. The CytoTRACE analysis suggests that NE dedifferentiated from the more differentiated Epithelial/AR-positive subtype, but this remains an active area of investigation. Finally, we are working to understand the Epithelial/AR and NE in DSRCT dimorphic states. Citation Format: Danh Truong, Emre Arslan, Veena Kochat, Sandhya Krishnan, Clement Agyemang, Margarita Divenko, Davis Ingram, Rossana Lascano, Akshay Basi, Javier Gomez, Hannah Beird, Chia-Chin Wu, Jared Burks, P Andrew Futreal, Alexander Lazar, Ravin Ratan, Najat Daw, Andrea Hayes, Kunal Rai, Joseph Ludwig. Multi-omic analysis of desmoplastic small sound cell tumors reveal distinct epithelial and neuroendocrine lineages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 130.

Desmoplastic Small Round Cell Tumors: Clinical Presentation, Molecular Characterization, and Therapeutic Approach of Seven Patients

Desmoplastic small round blue cell tumor (DSRCT) is a highly aggressive fatal sarcoma without evidence‐based therapeutic guidelines. We present here seven patients with DSRCT including immunohistochemistry combined with fluorescence in situ hybridization (FISH), next generation sequencing (NGS, n = 6) as well as OncoScan array (n = 3) analyses and show consecutive therapeutic approaches. All seven DSRCT patients presented with an extended abdominal mass; median age at diagnosis was 24.8 years. NGS analyses revealed five class 4 or 5 sequence variants. Remarkably, OncoScan and targeted analyses by FISH identified genomic gains of CCND1 in two cases. Cyclin D1 expression was present in all seven tumors as shown by immunohistochemical staining. Multimodal therapeutic concepts included systemic therapies, resection, and radiation. Six patients were treated as first‐line therapy with conventional chemotherapy. All except one patient had a dismal therapy response. Subsequent therapy lines consisted of chemotherapeutic combinations followed by targeted therapies. Due to Cyclin D1 expression, the CDK4/6 inhibitor palbociclib was applied to four patients. The median therapy duration until disease progression in these patients was 4.5 months (range, 1.5–5 months). So, CCND1 genomic gain and Cyclin D1 expression are common features pointing to cell‐cycle deregulation as a possible therapeutic target.

Desmoplastic small round cell tumor of abdomen: Case report of a very rare sarcoma with diagnostic challenge

Introduction: A desmoplastic small round blue cell tumor (DSRCT) is a very rare soft tissue sarcoma. The first case was reported in 1989 by Gerald and Rosai. Diagnosis can be challenging, and a differential diagnosis should be considered when a young patient presents with wide-spread abdominal disease without definitive organ involvement as shown in imaging studies. A typical radiological finding in DSRCT is a dominant solid mass in a retrovesical or rectouterine pouch with widespread peritoneal nodules. Case Report: In this case report, we present a case of a very rare sarcoma in a young Saudi male patient who presented with abdominal distension and widespread intra-abdominal disease with liver metastases. The dominant mass had a cystic component and was not in a typical site. Conclusion: Diagnosis of such sarcoma is challenging and it needs the correlation of clinical, radiological, morphological, immunohistochemical, and even genetic data.

Diagnostic Utility of Pax8, Pax2, and NGFR Immunohistochemical Expression in Pediatric Renal Tumors.

Pediatric renal tumors (PRT) with small round blue or spindle cell morphology can be diagnostically challenging and only a limited number of immunohistochemical markers have been documented to help in the diagnosis: paired box (Pax) 2 and nerve growth factor receptor (NGFR) positivity have been demonstrated in Wilms tumor (WT) and clear cell sarcoma of the kidney (CCSK), respectively. However, the immunohistochemical expression of these markers in other PRT remains unknown. This study investigated Pax8, Pax2, and NGFR immunophenotype in a large series of PRT. Pax8 and Pax2 showed an identical staining pattern, and were expressed in all (100%) WT while most CCSK were negative. All congenital mesoblastic nephromas, metanephric stromal tumors, primitive neuroectodermal tumors, desmoplastic small round blue cell tumors, most rhabdoid tumors, and synovial sarcomas were negative for Pax8. NGFR was expressed in 96% of CCSK (diffuse expression in 91%). Only a minority of WT stained for NGFR: 16% showed expression in the blastemal and 25% in the mesenchymal components. NGFR expression was noted in synovial sarcomas (67%, with diffuse expression seen in only 1 case, 8%), rhabdoid tumors (19%), cellular congenital mesoblastic nephromas (13%) and metanephric stromal tumors (12.5%). Primitive neuroectodermal tumors and desmoplastic small round blue cell tumors were negative for NGFR. In conclusion, Pax8/Pax2 and NGFR are sensitive markers for the diagnosis of WT and CCSK, respectively. However, their specificity is limited by variable reactivity within a subset of other renal neoplasms.

Feasibility of Administering A Modified Outpatient Regimen of Vincristine, Doxorubicin, Cyclophosphamide Alternating with Ifosfamide, and Etoposide (VAC/IE) For High-Risk Desmoplastic Small Round Blue Cell Tumor and the Role of Tumor Profiling in Selecting Treatments

Feasibility of Administering A Modified Outpatient Regimen of Vincristine, Doxorubicin, Cyclophosphamide Alternating with Ifosfamide, and Etoposide (VAC/IE) For High-Risk Desmoplastic Small Round Blue Cell Tumor and the Role of Tumor Profiling in Selecting Treatments

Potential therapeutic genomic alterations in desmoplastic small round blue cell tumor.

11066 Background: Desmoplastic Small Round Blue Cell Tumor (DSRCT) originates from a cell with multilineage potential. A molecular hallmark of DSCRT is the EWS-WT1 reciprocal translocation. Ewing’s and DSRCT are treated similarly due to similar oncogene activation pathways and DSRCT has been represented in very limited numbers in sarcoma studies. Methods: Thirty-five DSRCT tumors were tested with a multiplatform profiling service (Caris Life Sciences, Phoenix, AZ). Specific tests performed included sequencing (NextGen), protein expression (IHC) and gene amplification (CISH or FISH). Tumor mutational load (TML) was calculated as somatic nonsynonymous missense mutations sequenced with a 592-gene panel. Molecular alterations were compared to 88 Ewing sarcomas (ES). Chi-square tests were used for comparison and statistical significance was determined as p < 0.05. Results: In the 35 DSRCT tumors, high expression of TOP2A were seen in 63%, TOPO1 in 63%, PTEN in 62%, androgen receptor (AR) in 59%, EGFR in 42% of tumors; low expression of TUBB3 was seen in 44%, MGMT in 45%, TS in 48%, RRM1 in 57% and ERCC1 in 76% of tumors. When compared to ES, no significant difference was seen in protein expressions with the exception of a significantly higher overexpressson of AR in DSRCT (59% vs. 3%, p = 1.7E-10) and TUBB3 (56% vs. 29%, p = 0.03). Tumor expression of PD-L1 (Ab: SP142) was not seen in the 4 DSRCT and 10 ES tested. NextGen revealed a TP53 mutation (7%) and a FOXO3 mutation (L382fs) in DSCRT, while 6 TP53 mutations (13%), 2 APC mutations (L1129S and I1307K), 1 BRCA1(c.301+1G > A) and 1 CTNNB1 (T41A) mutation were identified in ES. Tumor mutational load evaluated in the 3 DSRCT and 11 ES tumors averaged 6 and 5 mutations per megabase, respectively. Conclusions: Molecular profiling on 35 DSRCT tumors and comparison with Ewing’s sarcoma revealed low immunogenicity ( < 10 Mutations/MB) and low frequency of actionable mutations including PD-L1 in both tumor types. High AR expression could present as a potential therapeutic target for DSRCT while taxanes may be more effective in Ewing’s sarcoma compared to DSCRT based on TUBB3 expression. Genomic and Molecular assessment may help determine the ideal regimen that will help achieve maximal tumor debulking.

Desmoplastic Small Round Blue Cell Tumor: A Review of Treatment and Potential Therapeutic Genomic Alterations.

Desmoplastic small round blue cell tumors (DSRCTs) originate from a cell with multilineage potential. A molecular hallmark of DSRCT is the EWS-WT1 reciprocal translocation. Ewing sarcoma and DSRCT are treated similarly due to similar oncogene activation pathways, and DSRCT has been represented in very limited numbers in sarcoma studies. Despite aggressive therapy, median survival ranges from 17 to 25 months, and 5-year survival rates remain around 15%, with higher survival reported among those undergoing removal of at least 90% of tumor in the absence of extraperitoneal metastasis. Almost 100% of these tumors contain t(11;22) (p13;q12) translocation, and it is likely that EWS-WT1 functions as a transcription factor possibly through WT1 targets. While there is no standard protocol for this aggressive disease, treatment usually includes the neoadjuvant HD P6 regimen (high-dose cyclophosphamide, doxorubicin, and vincristine (HD-CAV) alternating with ifosfamide and etoposide (IE) chemotherapy combined with aggressively attempted R0 resection). We aimed to review the molecular characteristics of DSRCTs to explore therapeutic opportunities for this extremely rare and aggressive cancer type.

Abstract 259: Novel peptide directed targeting of EWS-FLI1 impairs tumor cell growth

Abstract Introduction: Patients with Ewing's Sarcoma require improved therapy. EWS-FLI1 fusion protein provides a unique targeting opportunity. In the quest for protein partners, we identified a novel peptide sequence that binds to EWS-FLI1 using phage display. We hypothesize that by identifying peptides, and their cognate proteins, we can modulate the function of EWS-FLI1 to improve therapies for ESFT patients. Methods: Secreted peptide-alkaline phosphatase conjugates were used in ELISA for resolving binding regions. Cytotoxicity experiments were analyzed with MTT or WST reduction. Cell cycle analysis were performed using flow cytometry. Results: A phage display experiment to identify EWS-FLI1 peptides resulted in 96 phage clones that demonstrated binding to EWS-FLI1 by ELISA. Those 96 phage clones resulted in sequences that yielded twenty-seven unique peptides. Peptide A1 is one of 27 unique peptides that was commercially synthesized fused to penetratin (16aa) to facilitate intracellular transport. The cytotoxicity of A1 peptide was evaluated in TC32 and TC71 (EWS-FLI1, type I), A4573 (EWS-FLI1, type III), JN-DSRCT (desmoplastic small round blue cell tumor containing EWS-WT1), and SKNAS (a neuroblastoma cell line lacking EWS-FLI1 rearrangement). The IC50 level for A1 is between 5 -15 μM in cell lines bearing EWS fusion proteins. However, it is more than 50 μM in cells without the rearrangement. A1-alkaline phosphatase (A1-AP) conjugates were prepared with alanine substitutions throughout the peptide. Wild-type non-conjugated A1 competed away the interaction between the EWS-FLI1 and A1-AP, confirming its ability to bind to EWS-FLI1. Mutations in A1 demonstrated that the lysine residues are critical for binding to EWS-FLI1. The minimal interacting amino acids were validated using shortened and mutated versions of A1 in both ELISA and cell growth assays, including soft agar. A1 peptide blocked cell cycle progression of synchronized ESFT cells and caused accumulation at S phase. A1 peptide also inhibited EWS-FLI1 dependent transcription. Discussion: The A1 peptide directly binds to the EWS-FLI1 oncoprotein and leads to cell death in cells with either the EWS-FLI1 or EWS-WT1 fusion proteins. While A1 was discovered based on binding to EWS-FLI1; toxicity in JN-DSRCT studies suggest that the A1 peptide may have potency to EWS bearing fusion proteins. These findings present a novel method of targeting EWS rearranged oncoproteins and could lead to novel therapies Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 259. doi:10.1158/1538-7445.AM2011-259

Desmoplastic Small Cell Tumor With Bizarre Giant Nuclei

A case is reported of an intra-abdominal desmoplastic small cell tumor featuring giant bizarre nuclei, an event not previously recorded in this entity to the best of the authors' knowledge. The diagnosis was confirmed by immunohistochemistry and molecular genetics. A list is provided of the many other conditions in which this morphologically spectacular but clinically inconsequential nuclear change has been recorded.

Safety and Efficacy of Hematopoietic Stem Cell Remobilization with Plerixafor (Mozobil®) + G-CSF In Pediatric Patients with Malignant Disorders

AbstractAbstract 2245 Background:High dose chemo/radiotherapy followed by autologous hematopoietic stem cell (HSC) transplantation (HSCT) is indicated in several pediatric malignant disorders such as neuroblastoma and relapsed Hodgkin's disease. Ideally, 2–5 × 106 CD34+ cells/kg should be infused during autologous peripheral blood (PB) HSCT to support timely and durable engraftment and improve transplant outcomes. In patients who have received repetitive cycles of intensive chemotherapy, this target is not always achieved with standard mobilization regimens. Plerixafor, a novel CXCR4 antagonist, when combined with granulocyte colony-stimulating factor (G-CSF), can safely and predictably mobilize adequate numbers of CD34+ HSC to support transplantation in adult patients with myeloma and lymphoma. We report on the safety and efficacy of PB HSC mobilization with plerixafor + G-CSF in pediatric patients with cancer. Methods:This is a retrospective analysis of all children with various malignant disorders who were enrolled in the US plerixafor compassionate use program (CUP; NCT00291811). Patients who had previously failed HSC mobilization (defined as the inability to collect ≥2 x106 CD34+ cells/kg or achieve an adequate PB CD34+ cell count, typically ≥10 CD34+ cells/μl) with growth factor +/− chemotherapy were treated with plerixafor + G-CSF. The goal was to collect ≥2 × 106 CD34+ cells/kg for autologous HSCT. G-CSF (10μg/kg SC) was administered daily for 5 days. Plerixafor (0.24 mg/kg SC) was given in the evening on Day 4, ~11 hours prior to apheresis. Plerixafor, G-CSF and apheresis were repeated daily until ≥2 × 106 CD34+ cells/kg had been collected. Results:A total of 16 patients with non Hodgkin's lymphoma (3), Hodgkin's disease (1), CNS tumors (4), Ewing's sarcoma (4), neuroblastoma (2), osteogenic sarcoma (1) and desmoplastic small cell tumor (1) underwent the procedure. The median age was 14 years and 7 (44%) patients were male. In previous mobilization attempts, 5 patients failed to collect the minimum transplantable cell dose with a median yield of 0.44 x106 (range: 0.17–2.2 × 106) CD34+ cells/kg. Apheresis was never attempted in11 patients due to low PB CD34+ cell levels; median cells/μl was 1.0 (range, 0.01–12) in 9 patients with available data. Initial mobilization regimens included growth factor alone in 6 patients and growth factor + chemotherapy in 9 patients (data unavailable for 1 patient). When re-challenged for mobilization with plerixafor + G-CSF, 14 (88%) patients successfully collected ≥2 × 106 CD34+ cells/kg; this included all 4 (100%) patients with lymphoma and 10 (83%) patients with solid tumors. The median time to collect the target cell dose was 1.5 days (range 1–5 days). The median CD34+ cell yield from all patients was 3.5 × 106 cells/kg (range 0.96 – 9.80 × 106); patients with lymphoma and solid tumors collected a median of 7.2 (range 3.2 – 7.9) × 106 and 3.3 (range 0.96 –9.8) × 106 CD34+ cells/kg, respectively. Eleven (69%) patients proceeded to transplant including all 4 (100%) patients with lymphoma and 7 (58%) patients with solid tumors. One patient with neuroblastoma received a tandem transplant. The median infused cell dose was 4.18 × 106 CD34+ cells/kg (range 1.7 – 7.6 × 106). The median time to neutrophil and platelet engraftment was 14 and 33 days, respectively. Plerixafor-related adverse events were mostly mild, and observed in 5 (31%) patients. They included administration site reactions (4), vomiting (2), nausea (1) and oral paraesthesia (1). No patient experienced a serious adverse event. Conclusions:Treatment with plerixafor + G-CSF safely and effectively mobilized HSC in the majority of pediatric patients with malignant disorders after failure of standard mobilization with growth factor ± chemotherapy. Successful stem cell mobilization allowed consideration of autologous HSCT when indicated. Mobilization with plerixafor was safe and resulted in prompt engraftment. Many of these patients could not have proceeded to transplant without this intervention.Outcomes of plerixafor+ G-CSF remobilization in childrenNo. of Patients16Median age (range)14 (8–18)Gender, male (%)7 (44)Median CD34+ cells/kg × 106 collected (range)3.5 (0.96–9.80)No. of patients collecting ≥2 × 106 CD34+ cells/kg (%)14 (88)No. of patients proceeding to transplant (%)11 (69)Median days to neutrophil engraftment (range)14 (9–23)Median days to platelet engraftment (range)33 (12–86) Disclosures:Off Label Use: Plerixafor (Mozobil®), a hematopoietic stem cell mobilizer, is approved by the US FDA in combination with granulocyte-colony stimulating factor (G-CSF) to mobilize hematopoietic stem cells to the peripheral blood for collection and subsequent autologous transplantation in patients with non-Hodgkin's lymphoma and multiple myeloma. McCarty: Genzyme, Amgen: Honoraria, Research Funding. Angell: Genzyme Corporation: Employment, Equity Ownership. Huebner: Genzyme Corporation: Employment, Equity Ownership.

Cytoreductive surgery associated to hyperthermic intraperitoneal chemoperfusion for desmoplastic round small cell tumor with peritoneal carcinomatosis in young patients

Purpose Desmoplastic round small cell tumor (DRSCT) is a rare intraabdominal mesenchymal tissue neoplasm in young patients and spreads through the abdominal cavity. Its prognosis is poor despite a multimodal therapy including chemotherapy, radiotherapy, and surgical cytoreduction (CS). hyperthermic intraperitoneal chemotherapy (HIPEC) is considered as an additional strategy in the treatment of peritoneal carcinomatosis; for this reason, we planned to treat selected cases of children with DRSCT using CS and HIPEC. Methods Peritoneal disease extension was evaluated according to Gilly classification. Surgical cytoreduction was considered as completeness of cytoreduction-0 when no macroscopic nodule was residual; HIPEC was performed according to the open technique. Results We described 3 cases: the 2 first cases were realized for palliative conditions and the last one was operated on with curative intent. There was no postoperative mortality. One patient was reoperated for a gallbladder perforation. There was no other complication related to HIPEC procedure. Conclusions Surgical cytoreduction and HIPEC provide a local alternative approach to systemic chemotherapy in the control of microscopic peritoneal disease in DRSCT, with an acceptable morbidity, and may be considered as a potential beneficial adjuvant waiting for a more specific targeted therapy against the fusion protein.

Desmoplastic small cell tumor of soft tissue: Molecular variant of EWS‐WT1 chimeric fusion

A 7-year-old girl was hospitalized because of a tumorous mass in her left periorbital region. The tumor was removed by local excision. The soft-part tumor recurred in the parotid gland region 4 months later, and a second recurrence was noted on the left side of the neck 3 years and 3 months thereafter. The patient had not received chemotherapy or local irradiation. Histological and immunohistochemical examinations of the recurrent masses revealed morphological characteristics of small cell proliferation with desmoplastic stroma that were similar to those of the initial tumor. The cellular components showed immunoreactivity for desmin, cytokeratin, vimentin, and epithelial membrane antigen in part, but the cells were negative for myogenin, CD99, and neuron-specific enolase. These findings suggested a diagnosis of desmoplastic small cell tumor, despite its extra-abdominal location. The histological diagnosis was confirmed by reverse transcriptase polymerase chain reaction, which demonstrated an EWS-WT1 chimeric fusion gene. An in-frame fusion of EWS exon 9 and WT1 exon 8 was subsequently identified by cloning and sequencing. The chimeric fusion gene might be related to the tissue-specific phenotype of desmoplastic small cell tumors, although further investigation of this speculation is necessary.

Desmoplastic small cell tumor in the pancreas.

Desmoplastic small cell tumor (DSCT) is a distinct type of small blue cell tumors and is characterized by the unique karyotypic aberration involving the fusion of the Ewing's sarcoma (EWS) gene and Wilms' tumor (WT1) gene. Typically, it grows along serosal surfaces; however, in some cases, the tumor presents as a dominant mass in an internal organ. Examples of DSCT forming a primary mass in ovary, testes, and brain have been described, but its presentation as a primary pancreatic mass has not been reported previously. The case reported here is a 31-year-old woman who presented with a 14-cm mass in the pancreas. There were smaller nodules on the peritoneal surfaces that were regarded clinically as metastasis from a primary pancreatic tumor. During the frozen section, the diagnosis of a poorly differentiated endocrine carcinoma of pancreatic origin was rendered and patient underwent subtotal pancreatectomy. On microscopic examination, the tumor was composed of large nests and broad bands of small blue cells, separated by fibrous stroma. Immunohistochemical stains showed positivity of the tumor cells for cytokeratins (AE1:AE3 and CAM5.2), neuron specific enolase, desmin and WT1, whereas chromogranin, S-100, and CD99 were negative. Since this immunoprofile is characteristic of DSCT, molecular analysis was performed which revealed the presence of EWS-WT1 gene fusion characteristic of DSCT. This case shows that in addition to primary pancreatic tumors characterized by prominent cellularity such as solid pseudopapillary tumors, acinar cell carcinoma, pancreatoblastoma, endocrine tumors, and other small blue cell tumors, the differential diagnosis of cellular, stroma-poor neoplasia in the pancreas also includes DSCT. This case is also another demonstrative example of how DSCT may form a dominant mass in intraabdominal organs.

Unusual Aspects of Desmoplastic Small Round Cell Tumor

Desmoplastic small round cell tumor (DSRCT) is a neoplasia that occurs mainly in childhood and involves abdominal or peritoneal sites, coexpressing ectodermal and mesenchimal immunophenotypic markers, and is endowed with an impressive stromal desmoplasia that tends to decrease on tumor relapse. To date, over 150 cases have been collected in the literature. Its presumed neuroectodermal histogenesis has been challenged by cytogenetic findings different from those usually associated with neoplasms of neuroectodermal origin. The authors report a case bearing clinical and histologic aspects of typical desmoplastic retroperitoneal small cell tumor, with intense and diffuse nuclear immunopositivity for WT1, but lacking divergent immunophenotype. Ultrastructural investigation revealed that desmoplasia could result from fibrillary synthesis by neoplastic cells.

Percutaneous image-guided fine-needle aspiration of peritoneal lesions.

Fine-needle aspiration (FNA) is a widely accepted technique for the initial tissue diagnosis of a variety of lesions arising within retroperitoneal and intraabdominal viscera. Fear of complications secondary to perforation of the bowel wall has limited the use of FNA in the diagnosis of gastrointestinal and peritoneal masses. A variety of primary and secondary neoplasms involving the peritoneum may present as multiple nodules, as masses, or as diffuse involvement of the peritoneum. When these lesions are associated with mass lesions or areas of significant peritoneal thickening, they become amenable to percutaneous image-guided FNA. We report on our experience with a series of 23 peritoneal lesions investigated by FNA for which subsequent histologic confirmation was available in 19, along with an additional 4 cases without histologic confirmation. One to four passes were made into each lesion, and immediate assessment for adequacy was performed by a cytopathologist in all cases. All 17 cases with a specific cytologic diagnosis and histologic confirmation represented either primary or metastatic neoplasms (5 gastrointestinal stromal tumors, 4 metastatic melanomas, 2 mesotheliomas, 1 lymphoma, 1 example of Kaposi's sarcoma, 1 serous papillary carcinoma of ovarian origin, 1 mucinous adenocarcinoma of ovarian origin, 1 intraabdominal desmoplastic small-cell tumor, and 1 solitary fibrous tumor of the peritoneum). In an additional 4 cases, the aspirates were judged as insufficient for diagnosis, with the smears containing only blood and benign mesothelial cells and/or inflammatory cell elements. These four smears were associated with both neoplastic and nonneoplastic lesions. Surgical confirmation was obtained in only 2 of these cases (1 metastatic melanoma and 1 example of omental and peritoneal involvement by an ovarian adenocarcinoma). Two cases without histologic confirmation were associated with clinically confirmed metastases. In our series, no acute or chronic postprocedural complications were identified, indicating that FNA in this setting is a safe technique. Accurate cytologic diagnosis was achieved in 74% of cases. The overall insufficiency rate was 26%.

Neuroectodermal and neuroendocrine tumors principally seen in children.

Neuroectodermal tumors comprise a large proportion of childhood neoplasms. Neuroblastic tumors, including neuroblastoma, ganglioneuroblastoma, and ganglioneuroma, are the most frequent extracranial solid cancers of childhood, occurring primarily in infants and toddlers. Primitive neuroectodermal tumors, including Ewing sarcoma and peripheral neuroepitheliomas, occur most frequently in older children and adolescents, and as pediatric sarcomas are second in frequency only to rhabdomyosarcomas. Rarer neuroectodermal tumors include desmoplastic small cell tumors, esthesioneuroblastomas, and melanotic neuroectodermal tumors, the first two entities occurring as rather site-specific lesions in the abdomen and nose, respectively. Diagnosis can be difficult due to the undifferentiated nature of many of these cancers, but ancillary studies, including electron microscopy, immunohistochemistry, cytogenetics, and molecular genetics, enhance their recognition. The molecular nature of childhood neuroectodermal tumors is as diverse as their histology, ranging from the fusion genes characterizing the Ewing sarcoma family of tumors to the proto-oncogene amplification seen in aggressive neuroblastomas.

Hu Immunolabeling as a Marker of Neural and Neuroendocrine Differentiation in Normal and Neoplastic Human Tissues: Assessment Using a Recombinant Anti-Hu Fab Fragment.

The recombinant antibody fragment Fab GLN 495 recognizes an epitope shared by members of the neuron-associated Hu protein family (including HuC, HuD, and HelNl). This novel reagent labels the nuclei of neurons throughout the peripheral and central neuraxes and has been shown to recognize pulmonary small cell carcinomas and central nervous system (CNS) tumors of mature neuronal phenotype or neuronogenic differentiating capacity. Using this Fab fragment, we have undertaken a systematic survey of normal human tissues and an assessment of 554 non-CNS tumor samples for immunohistochemical evidence of Hu expression. Adrenomedullary cells, pancreatic islet cells, paraganglial chief cells, isolated adenohypophyseal cells, and spermatogonia were the only nonneuronal normal tissue elements to bind Fab GLN 495. In addition to labeling all 10 small cell carcinomas studied (six of which were extrapulmonary in origin), this recombinant anti-Hu Fab proved immunoreactive with neuroblastomas (four/four), esthesioneuroblastomas (one/one), typical (three/four) and atypical (one/four) pulmonary carcinoids, pancreatic islet cell tumors (two/six), large-cell neuroendocrine carcinoma of lung (one/four), Merkel cell tumors (two/three), medullary carcinomas of the thyroid (four/six), pheochromocytomas (two/four) and paragangliomas (four/four). Nonneural/neuroendocrine tumor labeling was restricted to the neuronal and immature neuroepithelial components of teratomas, to extraskeletal myxoid chondrosarcomas (three/four) and to small subsets of cells within examples of renal rhabdoid tumor (one/four), desmoplastic small cell tumor (one/four), alveolar rhabdomyosarcoma (two/four), Ewing sarcoma/PNET (two/nine), and Wilms tumor (one/four). Immunoreactivity was principally nuclear, with variable cytoplasmic labeling. Our findings support the largely restricted expression of Hu by neural/neuroendocrine neoplasms, suggest a potential role for Fab GLN 495 in the identification of small cell carcinomas irrespective of primary site, and support a recent proposal that at least some extraskeletal myxoid "chondrosarcomas" actually represent neuroendocrine tumors of soft parts. Int J Surg Pathol 8(2):109-117, 2000

CD31 Immunoreactivity in Small Round Cell Tumors

CD31 has been shown to be a sensitive and specific marker for endothelial differentiation among epithelioid and spindled-pleomorphic human neoplasms. However, the role of this marker in the evaluation of small round cell tumors has not been evaluated. Formalin-fixed, paraffin-embedded tissue sections from 276 small round cell tumors, including 85 Ewing's sarcoma/primitive neuroectodermal tumors (ES/PNET), 52 rhabdomyosarcomas, 10 extraabdominal polyphenotypic small cell tumors, six desmoplastic small cell tumors, 11 neuroblastomas, 23 Wilms' tumors, 20 retinoblastomas, 13 esthesioneuroblastomas, and 56 small cell malignant lymphomas were stained with CD31 (JC/70A, 1:40), using a modified avidinbiotin-peroxidase complex technique, after citrate buffer microwave epitope retrieval. Among nonlymphoid small round cell tumors, four of 85 ES/PNET were at least focally reactive. No other lesion in this group was positive. In contrast, the majority of well-differentiated (11 of 17), intermediately differentiated (two of three), and lymphoblastic lymphomas (three of three) were positive. Small cleaved lymphomas (three of 13 follicular, one of 13 diffuse) were less often reactive, whereas small noncleaved lesions were negative. Although reactivity for CD31 in ES/PNET is uncommon, the presence of platelet/endothelial cell adhesion molecule in a small cell neoplasm should not in isolation be taken as evidence of hematopoietic origin. These results further define the utility of CD31 in the evaluation of human neoplasms.

Molecular genetics in the diagnosis and prognosis of solid pediatric tumors.

The field of molecular genetics continues to see an ever increasing number of applications to pediatric tumor analysis. Studies in pediatric tumors have identified novel genes and other genetic changes, a large number of which reflect one of the following mechanisms: (1) activation of proto-oncogenes; (2) loss of tumor suppressor genes; or (3) creation of novel fusion proteins. At least one of these mechanisms is operational in each of the following pediatric tumors: neuroblastoma, Ewing sarcoma and peripheral primitive neuroectodermal tumor (pPNET), intra-abdominal desmoplastic small-cell tumor, rhabdomyosarcoma, synovial sarcoma, and Wilms tumor. Out of this research has come not only an increased understanding of oncogenesis but also, for each of the tumors listed above, diagnostic and/or prognostic markers that can be used by the pathologist and oncologist to improve overall patient management.

Intra-abdominal desmoplastic small cell tumor presenting as an acute abdomen after trauma

The intraperitoneal mass most commonly encountered after blunt abdominal truama is a hematoma. However, one must also consider unusual bulky tumors that can have imaging characteristics similar to those of hematoma. The most typical of these neoplasms is lymphoma, but a desmoplastic small cell tumor also may be observed. The presentation and imaging findings of a desmoplastic small tumor are described.