Paratesticular desmoplastic small round cell tumour: an unusual tumour with an unusual fusion; cytogenetic and molecular genetic analysis combining RT-PCR and COBRA-FISH

EWSR1::WT1 Fusions in Neoplasms Other Than Conventional Desmoplastic Small Round Cell Tumor: Three Tumors Occurring Outside the Female Genital Tract

Desmoplastic small round cell tumor (DSRCT) is a high-grade, primitive round cell sarcoma classically associated with prominent desmoplastic stroma, coexpression of keratin and desmin, and a characteristic EWSR1::WT1 gene fusion. DSRCT typically arises in the abdominopelvic cavity of young males with diffuse peritoneal spread and poor overall survival. Although originally considered to be pathognomonic for DSRCT, EWSR1::WT1 gene fusions have recently been detected in rare tumors lacking the characteristic morphologic and immunohistochemical features of DSRCT. Here, we report 3 additional cases of neoplasms other than conventional DSCRCT with EWSR1::WT1 gene fusions that occurred outside the female genital tract. Two occurred in the abdominopelvic cavities of a 27-year-old man and a 12-year-old girl, whereas the third arose in the axillary soft tissue of an 85-year-old man. All cases lacked prominent desmoplastic stroma and were instead solid and cystic with peripheral fibrous pseudocapsules and occasional intervening fibrous septa. Necrosis was either absent (1/3) or rare (2/3), and mitotic activity was low (<1 to 3 per 10 hpf). In immunohistochemical studies, there was expression of smooth muscle actin (3/3) and desmin (3/3), rare to focal reactivity for EMA (2/3), and variable expression of CK AE1/AE3 (1/3). Myogenin and MyoD1 were negative, and C-terminus-specific WT1 was positive in both cases tested (2/2). All 3 tumors followed a more indolent clinical course with 2 cases demonstrating no evidence of disease at 20 and 44 months after resection. The patient from case 3 died of other causes at 14 months with no evidence of recurrence. DNA methylation profiling showed that the 3 cases clustered with DSRCT; however, they demonstrated fewer copy number variations with 2 cases having a flat profile (0% copy number variation). Differential methylation analysis with hierarchical clustering further showed variation between the 3 cases and conventional DSRCT. Although further study is needed, our results, in addition to previous reports, suggest that EWSR1::WT1 gene fusions occur in rare and seemingly distinctive tumors other than conventional DSRCT with indolent behavior. Proper classification of these unusual soft tissue tumors with EWSR1::WT1 gene fusions requires direct correlation with tumor morphology and clinical behavior, which is essential to avoid overtreatment with aggressive chemotherapy.

Selective Immunoreactivity for WT1 Carboxy-Terminus Distinguishes Desmoplastic Small Round Cell Tumor From its Histologic Mimics

Desmoplastic small round cell tumor (DSRCT) is an aggressive pediatric round cell sarcoma containing a characteristic EWSR1-WT1 gene fusion. In the absence of genetic data, distinguishing DSRCT from other small round cell tumors of childhood can be problematic due to overlapping histologic and immunohistochemical features. We studied the utility of immunohistochemistry with antibodies targeting both the amino-terminal and carboxy-terminal regions of the Wilms tumor-1 (WT1) protein in differentiating these groups of tumors. The study cohort included 33 cases of genetically confirmed pediatric round cell tumors (10 DSRCTs, 12 Wilms tumors, 10 Ewing sarcomas, and 1 CIC-rearranged sarcoma). Immunoreactivities and immunolocalization of both the WT1 amino-terminus and carboxy-terminus were scored and documented. All DSRCTs displayed selective reactivity for only the WT1 carboxy-terminus (10/10), while dual immunoreactivity for both the WT1 carboxy-terminus (12/12) and amino-terminus antibodies (12/12) were characteristic of Wilms tumors. CIC-rearranged sarcoma showed variable WT1 nuclear immunopositivity (1/1, 1/1) and Ewing sarcomas were consistently WT1-negative for both the WT1 amino-terminus (0/10) and carboxy-terminus (0/10). Dual WT1 amino-terminus and carboxy-terminus immunohistochemistry remains a helpful diagnostic tool in discriminating intraabdominal small round cell tumors, which serves as an adjunct to the genetic information in preventing misdiagnosis.

Exploiting LRRC15 as a novel therapeutic target in cancer

Abundant fibrotic stroma is a typical feature of most solid tumors, and stromal activation promotes oncogenesis, therapy resistance, and metastatic dissemination of cancer cells. Therefore, targeting the tumor stroma in combination with standard-of-care therapies has become a promising therapeutic strategy in recent years. The leucine-rich repeat-containing protein (LRRC15) is involved in cell-cell and cell-matrix interactions and came into focus as a promising anti-cancer target owing to its overexpression in mesenchymal-derived tumors such as sarcoma, glioblastoma, and melanoma and in cancer-associated fibroblasts in the microenvironment of breast, head and neck, lung, and pancreatic tumors. Effective targeting of LRRC15 using specific antibody-drug conjugates (ADC) has the potential to improve the outcome of patients with LRRC15-positive cancers of mesenchymal origin or stromal desmoplasia. Moreover, LRRC15 expression may serve as a predictive biomarker that could be utilized in the preclinical assessment of cancer patients to support personalized clinical outcomes. This review focuses on the role of LRRC15 in cancer, including clinical trials involving LRRC15-targeted therapies, such as the ABBV-085 ADC for patients with LRRC15-positive tumors. This review spans perceived knowledge gaps and highlights the clinical avenues that need to be explored to provide better therapeutic outcomes in patients.

Label-free proteomics differences in the dorsolateral prefrontal cortex between bipolar disorder patients with and without psychosis

BACKGROUND

Psychosis is common in bipolar disorder (BD) and is related to more severe cognitive impairments. Since the molecular mechanism of BD psychosis is elusive, we conducted this study to explore the proteomic differences associated with BD psychosis in the dorsolateral prefrontal cortex (DLPFC; BA9).

METHODS

Postmortem DLPFC gray matter tissues from five pairs of age-matched male BD subjects with and without psychosis history were used. Tissue proteomes were identified and quantified by label-free liquid chromatography tandem mass spectrometry and then compared between groups. Statistical significance was set at q < 0.40 and Log₂ fold change (Log₂FC) ≥ |1|. Protein groups with differential expression between groups at p < 0.05 were subjected to pathway analysis.

RESULTS

Eleven protein groups differed significantly between groups, including the reduction of tenascin C (q = 0.005, Log₂FC = -1.78), the elevations of synaptoporin (q = 0.235, Log₂FC = 1.17) and brain-specific angiogenesis inhibitor 1-associated protein 3 (q = 0.241, Log₂FC = 2.10) in BD with psychosis. The between-group differences of these proteins were confirmed by Western blots. The top enriched pathways (p < 0.05 with ≥ 3 hits) were the outgrowth of neurons, neuronal cell proliferation, growth of neurites, and outgrowth of neurites, which were all predicted to be upregulated in BD with psychosis.

LIMITATIONS

Small sample size and uncertain relationships of the observed proteomic differences with illness stage and acute psychosis.

CONCLUSIONS

These results suggested BD with psychosis history may be associated with abnormalities in neurodevelopment, neuroplasticity, neurotransmission, and neuromodulation in the DLPFC.

Irinotecan and vincristine for the treatment of refractory desmoplastic small round cell tumor in a developing country: a case report

Introduction

Desmoplastic small round cell tumor is an extremely rare and aggressive cancer that affects mainly adolescents and young adults. Despite multiple therapeutic strategies, most patients have resistant disease with very poor survival rates.

Case presentation

We present a case of a 10-year-old Caucasian boy with a desmoplastic small round cell tumor refractory to conventional treatment who exhibited a good response to alternative treatment. With use of irinotecan and vincristine in association with radiation therapy, a reduction of 96.9% of the dimensions of the target lesions compared with the initial image was observed.

Conclusion

This chemotherapy regimen, in association with radiation therapy, demonstrated efficacy for refractory desmoplastic small round cell tumor in our patient, and it is cost-effective.

Paratesticular desmoplastic small round cell tumors: A case report and review of the literature

Desmoplastic small round cell tumor (DSCRT) is a rare malignancy most often seen in the abdomen or pelvis of young men. Unfortunately, this disease is usually metastatic at diagnosis and has dismal outcomes. We describe a case of isolated paratesticular DSCRT in a 14-year-old male successfully treated with surgical resection, chemotherapy, and adjuvant radiation, and we present a review of the relevant literature. It appears that isolated, paratesticular DSCRTs have a markedly better outcome than the classic abdominal or pelvic location. We hypothesize that this is due to earlier detection and the relative ease of surgical resection.

Desmoplastic small round cell tumor: evaluation of reverse transcription-polymerase chain reaction and fluorescence in situ hybridization as ancillary molecular diagnostic techniques

Desmoplastic small round cell tumor (DSRCT) is a rare, biologically aggressive soft tissue neoplasm of uncertain differentiation, most often arising in the abdominal and pelvic cavities of adolescents and young adults with a striking male predominance. Histologically, it is characterized by islands of uniform small round cells in prominent desmoplastic stroma, and it has a polyimmunophenotypic profile, typically expressing WT1 and cytokeratin, desmin, and neural/neuroendocrine differentiation markers to varying degrees. Tumors at other sites and with variant morphology are more rarely described. DSRCT is associated with a recurrent t(11;22)(p13;q12) translocation, leading to the characteristic EWSR1-WT1 gene fusion. Fluorescence in situ hybridization (FISH), to detect EWSR1 rearrangement, and reverse transcription-polymerase chain reaction (RT-PCR) to assess for EWSR1-WT1 fusion transcripts are routine diagnostic ancillary tools. We present a large institutional comparative series of FISH and RT-PCR for DSRCT diagnosis. Twenty-six specimens (from 25 patients) histologically diagnosed as DSRCT were assessed for EWSR1 rearrangement and EWSR1-WT1 fusion transcripts. Of these 26 specimens, 24 yielded positive results with either FISH or RT-PCR or both. FISH was performed in 23 samples, with EWSR1 rearrangement seen in 21 (91.3%). RT-PCR was performed in 18 samples, of which 13 (72.2%) harbored EWSR1-WT1 fusion transcripts. The sensitivity of FISH in detecting DSRCT was 91.3%, and that of RT-PCR was 92.8% following omission of four technical failures. Therefore, both methods are comparable in terms of sensitivity. FISH is more sensitive if technical failures for RT-PCR are taken into account, and RT-PCR is more specific in confirming DSRCT. Both methods complement each other by confirming cases that the other method may not. In isolation, FISH is a relatively non-specific diagnostic adjunct due to the number of different neoplasms that can harbor EWSR1 rearrangement, such as Ewing sarcoma. However, in cases with appropriate morphology and a typical pattern of immunostaining, FISH is confirmatory of the diagnosis.

Desmoplastic Small Round Cell Tumor

Desmoplastic small round cell tumor (DSRCT) is an aggressive small round cell neoplasm which predominantly occurs intra-abdominally in adolescents and young adults with a male predominance, and which is characterized by a recurrent t(11;22)(p13;q12) translocation leading to formation of the EWSR1-WT1 fusion gene, which generates a chimeric protein with transcriptional regulatory activity. Histologically, DSRCT has a characteristic morphology, of islands of monotonous small cells within prominent sparsely cellular fibroblastic stroma, and immunohistochemically it shows polyphenotypic multidirectional differentiation, with expression of epithelial, muscle, and neural markers. However, DSRCT can arise more rarely in other sites and exhibit a spectrum of both histologic features and immunoprofile, which may confuse diagnosis with other small round cell neoplasms. Correct diagnosis is important to ensure correct treatment and prognostication; DSRCT are almost universally fatal neoplasms with patients usually succumbing to disease within the first 2 years of diagnosis. While combination treatment strategies can confer a survival benefit, the overall prognosis remains poor. Further insight into the tumorigenic molecular changes generated by the fusion oncogene may lead to the generation of specific targeted therapies. We review DSRCT, discussing morphology and immunohistochemistry, molecular genetic findings, potential targeted treatments, and the differential diagnosis.

Desmoplastic small round cell tumor: a rare cause of a progressive brachial plexopathy

INTRODUCTION

Desmoplastic small round cell tumor (DSRCT) is an uncommon, embryonic-type neoplasm, typically presenting as an abdominal mass in young men. A single case of DSRCT arising in the peripheral nervous system has been reported previously.

METHODS

The clinical course, imaging, electrophysiological, intraoperative, histopathological, molecular findings, and postoperative follow-up are reported.

RESULTS

A 43-year-old man presented with slowly progressive right brachial plexopathy. Magnetic resonance imaging revealed an enlarged medial cord with heterogeneous contrast enhancement. Histology showed a "small round cell" neoplasm with a polyphenotypic immunoprofile, including epithelial and mesenchymal markers. A pathognomonic fusion of Ewing sarcoma breakpoint region 1 and Wilms tumor 1 genes (EWSR1/WT1) was present. Treatment involved gross total excision and local radiotherapy.

CONCLUSIONS

Our findings confirm the occurrence of DSRCT as a primary peripheral nerve tumor. Despite its usually very aggressive clinical course, prolonged recurrence-free survival may be reached. Histomorphology and immunoprofile of DSRCT may lead to misdiagnosis as small cell carcinoma.