CIC-DUX4 gene fusion, resulting from either a t(4;19) or t(10;19) translocation, is the most common genetic abnormality detected in EWSR1-negative small blue round cell tumors (SBRCTs). Following their discovery it was debated if these tumors should be classified as variants of Ewing sarcoma (i.e. atypical Ewing sarcoma) or as a stand-alone pathologic entity. As such the WHO classification temporarily grouped the CIC-rearranged tumors under undifferentiated sarcomas with round cell phenotype, until further clinical evidence was available. However, most studies reported so far include small series with limited follow-up information which preclude a more definitive assessment. The present work investigates the clinicopathologic features of a large cohort of sarcomas with CIC gene rearrangement, in order to define their clinical presentation, morphologic spectrum, and outcome. Our study further examines the overall survival of the CIC-positive cohort compared to a control group of EWSR1-rearranged Ewing sarcoma matched for age and stage. The study cohort included 115 patients, with a mean age of 32 years and a slight male predominance. Most tumors occurred in the soft tissue (86%), predominantly deep-seated and equally divided among trunk and extremity, followed by visceral locations (12%) and rarely in the bone (3%). Microscopically, most tumors showed round to ovoid cytomorphology but half of the cases showed also focal areas of spindling and epithelioid/rhabdoid phenotype, with frequent myxoid stromal changes. Variable CD99 reactivity was seen in 84% cases, with a diffuse pattern only in 23% of cases, while nuclear WT1 was seen in 92%. A CIC-DUX4 fusion was detected in 57% of cases, with either DUX4 on 4q35 (35%) or on 10q26 in 25 (22%) cases. No FOXO4 gene rearrangements were present in 39 cases tested. Clinical follow-up was available in 57 patients, with a 5-year survival of 43%, which was significantly lower than the 77% 5-year survival in the control Ewing sarcoma group (p=0.002). Our findings show that CIC-DUX4 sarcomas occur most commonly in young adults within the somatic soft tissues, having a wide spectrum of morphology including round, epithelioid and spindle cells, and associated with an aggressive clinical course, with an inferior overall survival compared to Ewing sarcoma. The results support the classification of CIC-rearranged tumors as an independent molecular and clinical subset of SBRCTs distinct from Ewing sarcoma.
Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 has led to a global public health crisis. In elderly individuals and those with comorbidities, COVID-19 is associated with high mortality, frequently caused by acute respiratory distress syndrome. We examine in situ expression of SARS-CoV-2 in airways and lung obtained at autopsy of individuals with confirmed COVID-19 infection. Seven autopsy cases (male, N = 5; female, N = 2) with reverse transcriptase-polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infection and a median age of 66 years (range, 50-77 years) were evaluated using a rabbit polyclonal antibody against SARS Nucleocapsid protein in correlation with clinical parameters. The median time from symptom onset to death was 9 days (range, 6-31 days), from hospitalization 7 days (range, 1-21 days), from positive RT-PCR 7 days (range, 0-18 days), and from intensive care unit admission defining onset of respiratory failure 3 days (range, 1-18 days). Chest imaging identified diffuse airspace disease in all patients corresponding to acute and (N = 5) or organizing (N = 2) diffuse alveolar damage (DAD) on histologic examination. Among five patients with acute-phase DAD (≤7 days from onset of respiratory failure), SARS-CoV-2 was detected in pulmonary pneumocytes and ciliated airway cells (N = 5), and in upper airway epithelium (N = 2). In two patients with organizing DAD (>14 days from onset of respiratory failure), no virus was detected in lungs or airways. No endothelial cell infection was observed. The findings suggest that SARS-CoV-2 infection of epithelial cells in lungs and airways of patients with COVID-19 who developed respiratory failure can be detected during the acute phase of lung injury and is absent in the organizing phase.
The diagnosis of malignant peripheral nerve sheath tumor is challenging, particularly in the sporadic setting. Inactivation of the polycomb repressive complex 2 (PRC2), resulting from inactivating mutations of its constituents SUZ12 or EED1, has recently been identified in 70-90% of malignant peripheral nerve sheath tumors. Homozygous PRC2 inactivation results in loss of histone H3K27 trimethylation (H3K27me3). PRC2 inactivation promotes tumor progression and may render patients sensitive to epigenetic-based targeted therapies. H3K27me3 loss has not yet been validated as a diagnostic marker. We evaluated immunohistochemistry for H3K27me3 in 100 malignant peripheral nerve sheath tumors (70 sporadic, 10 neurofibromatosis type 1-associated, 10 radiation-associated, 10 epithelioid) and 200 other spindle cell neoplasms representing potential mimics (20 each monophasic synovial sarcoma, leiomyosarcoma, dedifferentiated liposarcoma, malignant solitary fibrous tumor, low-grade fibromyxoid sarcoma, cellular schwannoma, spindle cell melanoma, unclassified postradiation sarcoma; 10 each atypical neurofibroma, spindle cell rhabdomyosarcoma, gastrointestinal stromal tumor, fibrosarcomatous dermatofibrosarcoma protuberans). In total, 51 (51%) malignant peripheral nerve sheath tumors, including 34 (49%) sporadic, 7 (70%) neurofibromatosis type 1-associated, and 10 (100%) radiation-associated, but no epithelioid malignant peripheral nerve sheath tumors, were negative for H3K27me3. An additional 6 (6%) tumors showed heterogeneous H3K27me3 expression. Among the 90 sporadic, neurofibromatosis type 1-associated, and radiation-associated malignant peripheral nerve sheath tumors, complete H3K27me3 loss was observed in 29% of low-grade, 59% of intermediate-grade, and 83% of high-grade tumors (low vs intermediate/high grade, P = 0.0003). Among other tumor types, 4 (20%) unclassified postradiation sarcomas were negative for H3K27me3, whereas all other neoplasms were positive. Loss of H3K27me3 is highly specific for malignant peripheral nerve sheath tumor (although only modestly more sensitive than S-100 protein and SOX10) and may be a useful diagnostic marker. Our findings suggest that PRC2 inactivation in malignant peripheral nerve sheath tumor may occur during progression to higher grades.
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