Inflammatory pseudotumour is a generic term applied to a variety of neoplastic and non-neoplastic entities that share a common histological appearance, namely a cytologically bland spindle cell proliferation with a prominent, usually chronic inflammatory infiltrate. Over the last two decades, inflammatory myofibroblastic tumour (IMT) has emerged from within the broad category of inflammatory pseudotumour, with distinctive clinical, pathological and molecular features. IMT shows a predilection for the visceral soft tissues of children and adolescents and has a tendency for local recurrence, but only a small risk of distant metastasis. Characteristic histological patterns include the fasciitis-like, compact spindle cell and hypocellular fibrous patterns, which are often seen in combination within the same tumour. Chromosomal translocations leading to activation of the ALK tyrosine kinase can be detected in approximately 50% of IMTs, particularly those arising in young patients. This review will examine the clinical, pathological, and molecular genetic features of IMT and discuss an approach to diagnosis and differential diagnosis.

To the Editor: Neurologic symptoms, including headache, altered mental status, and anosmia, occur in many patients with Covid-19. [1][2][3] We report the neuropathological findings from autopsies of 18 consecutive patients with SARS-CoV-2 infection who died in a single teaching hospital between April 14 and April 29, 2020.All the patients had nasopharyngeal swab samples that were positive for SARS-CoV-2 on qualitative reverse-transcriptase-polymerase-chainreaction (RT-PCR) assays. The median age was 62 years (interquartile range, 53 to 75), and 14 patients (78%) were men. The presenting neurologic symptoms were myalgia (in 3 patients), headache (in 2), and decreased taste (in 1). Coexisting conditions included diabetes mellitus (in 12 patients), hypertension (in 11), cardiovascular disease (in 5), hyperlipidemia (in 5), chronic kidney disease (in 4), prior stroke (in 4), dementia (in 4), and treated anaplastic astrocytoma (in 1) (see Tables S1 and S2 in the Supplementary Appendix, available with the full text of this letter at NEJM.org).The patients had presented a median of 2 days (interquartile range, 0 to 5) after the onset of the first symptoms of SARS-CoV-2 infection and were hospitalized for a median of 6 days (interquartile range, 2 to 9) before death (Fig. S1A); 11 received mechanical ventilation. According to a retrospective chart review by neurologists, all the patients had a confusional state or decreased arousal from sedation for ventilation. Brain magnetic resonance imaging, electroencephalographic imaging, and cerebrospinal fluid examinations were not performed. Cranial computed tomography without contrast was performed in 3 patients and showed no acute abnormalities; the tumor resection cavity in the patient with a known anaplastic astrocytoma was seen.Death occurred 0 to 32 days after the onset of symptoms (median, 8 days; mean, 10 days). Autopsies were performed in a uniform manner with sampling of 10 standard brain areas. Specimens were fixed in formalin and stained with hema-

SUMMARY Sarcomas are a broad family of mesenchymal malignancies exhibiting remarkable histologic diversity. We describe the multi-platform molecular landscape of 206 adult soft tissue sarcomas representing 6 major types. Along with novel insights into the biology of individual sarcoma types, we report three overarching findings: 1) unlike most epithelial malignancies, these sarcomas (excepting synovial sarcoma) are characterized predominantly by copy number changes, with low mutational loads and only a few genes (TP53, ATRX, RB1) highly recurrently mutated across sarcoma types, 2) within sarcoma types, genomic and regulomic diversity of driver pathways defines molecular subtypes associated with patient outcome, and 3) the immune microenvironment, inferred from DNA methylation and mRNA profiles, associates with outcome and may inform clinical trials of immune checkpoint inhibitors. Overall, this large-scale analysis reveals previously unappreciated sarcoma type-specific changes in copy number, methylation, RNA, and protein, providing insights into refining sarcoma therapy and relationships to other cancer types.

SUMMARYInflammatory myofibroblastic tumor (IMT) is a distinctive mesenchymal neoplasm characterized by a spindle-cell proliferation with an inflammatory infiltrate. Approximately half of IMTs carry rearrangements of the anaplastic lymphoma kinase (ALK) locus on chromosome 2p23, causing aberrant ALK expression. We report a sustained partial response to the ALK inhibitor crizotinib (PF-02341066, Pfizer) in a patient with ALK-translocated IMT, as compared with no observed activity in another patient without the ALK translocation. These results support the dependence of ALK-rearranged tumors on ALK-mediated signaling and suggest a therapeutic strategy for genomically identified patients with the aggressive form of this soft-tissue tumor.Inflammatory myofibroblastic tumors (IMTS) occur primarily during the first two decades of life and typically arise in the lung, retroperitoneum, or abdominopelvic region. 1,2 Abdominal tumors may be multifocal. Lesional cells are predominantly myofibroblasts in a myxoid to collagenous stroma admixed with inflammatory cells. 2,3 Local recurrence may occur after initial surgery, with a low risk of distant metastases, 1,2 so that IMTs are considered to be soft-tissue tumors of intermediate biologic potential, with a small fraction behaving aggressively. 4 Rearrangements involving the ALK locus on chromosome 2p23 have been documented in approximately 50% of IMTs. 5,6 ALK aneuploidy has also been described, with a gain in copy number without rearrangement. 5 Among cancers with rearrangements, several fusion partners have been identified that serve to constitutively activate ALK. 7-10 ALK expression reliably correlates with ALK rearrangement. 11 Distant metastases occur primarily in ALKnegative IMTs, but local recurrence occurs regardless of ALK expression. 5 Several ALK fusion proteins, including TPM3-ALK found in IMT, induce transformation in cell lines and animal models, 13 a finding that suggests that ALK rearrangement may define a subgroup of IMTs that is sensitive to targeted kinase inhibition. We therefore enrolled two patients with IMT in a dose-escalation phase 1 trial of crizotinib, an orally bioavailable ATP-competitive inhibitor of the ALK and MET tyrosine kinases. 14,15 CASE REPORTSPatient 1 was a 44-year-old man who had been well until May 2007, when he reported having early satiety and abdominal pain. Computed tomography (CT) of the abdomen and pelvis revealed ascites, a mass in the right upper quadrant, and omental caking. The results of esophagogastroduodenoscopy and colonoscopy were unremarkable. The patient then underwent paracentesis. Combined 18 F-fluorodeoxyglucose positron-emission tomography and CT (FDG-PET-CT) revealed hypermetabolic masses in the abdomen and pelvis. In June 2007, he underwent exploratory laparotomy, which showed massive omental caking with discrete, round, gelatinous, grape-size tumor nodules and extensive peritoneal disease. Maximal tumor debulking was performed along with catheter placement to facilitate administration of a hyperthermic periton...