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In this inaugural clinicopathological conference, the invited experts discussed the diagnostic approach to central nervous system infections in immunocompromised hosts. The case presented involved a pancreas‐kidney transplant recipient with multiple brain abscesses caused by Bartonella henselae. CSF metagenomic next‐generation sequencing played a significant role in the diagnosis. Bartonella henselae is a gram‐negative zoonotic pathogen that causes cat‐scratch disease, which can be transmitted to humans through cat bites or scratches. Symptoms can vary in severity, correlating with the patient's immune status. Visceral organ involvement, ocular involvement, and neurological manifestations have been reported in immunocompromised patients, but brain abscesses are rare. [ABSTRACT FROM AUTHOR]

Mucoepidermoid carcinomas (MEC) are the most common malignant neoplasms of salivary glands, but are uncommon in other sites. Salivary gland MEC are most frequently associated with CRTC1--MAML2 translocations. Exceedingly rare MEC of the breast demonstrate a basal-like and often triple (oestrogen and progesterone receptor, HER2)-negative immunophenotype, with a single case previously reported to show MAML2 rearrangement, although the fusion partner was not known. Comprehensive genomic studies of breast MEC are lacking. In this study, we analysed the immunophenotype and molecular landscape of two breast MEC to elucidate the pathogenesis of these rare tumours. Methods and results: Two breast MEC were subjected to capture-based next-generation DNA sequencing of 479 cancer-related genes. The presence of the CRTC1--MAML2 fusion transcript was interrogated by reverse transcriptase--polymerase chain reaction. In addition, the immunoprofiles of breast MEC were compared to salivary gland MEC. Both breast MEC harboured CRTC1--MAML2 fusions. In contrast to most triple-negative breast carcinomas of no special type, the mutational burden of MEC was very low, with one case demonstrating only an inactivating SETD2 mutation, and the other harbouring no somatic variants in genes on the panel. No copy number alterations were identified. The immunopro- files of breast and salivary gland MEC were overlapping, but not identical. Conclusions: The findings highlight MEC as a breast cancer subtype more closely related to its salivary gland counterpart than to basal-like/triple-negative breast cancers of no special type. [ABSTRACT FROM AUTHOR]

Anaplasia may be identified in a subset of tumors with a presumed pilocytic astrocytoma (PA) component or piloid features, which may be associated with aggressive behavior, but the biologic basis of this change remains unclear. Fifty‐seven resections from 36 patients (23 M, 13 F, mean age 32 years, range 3–75) were included. A clinical diagnosis of NF1 was present in 8 (22%). Alternative lengthening of telomeres (ALT) was assessed by telomere‐specific FISH and/or CISH. A combination of immunohistochemistry, DNA sequencing and FISH were used to study BRAF,ATRX,CDKN2A/p16, mutant IDH1 p.R132H and H3‐K27M proteins. ALT was present in 25 (69%) cases and ATRX loss in 20 (57%), mostly in the expected association of ALT+/ATRX‐ (20/24, 83%) or ALT‐/ATRX+ (11/11, 100%). BRAF duplication was present in 8 (of 26) (31%). H3‐K27M was present in 5 of 32 (16%) cases, all with concurrent ATRX loss and ALT. ALT was also present in 9 (of 11) cases in the benign PA precursor, 7 of which also had ATRX loss in both the precursor and the anaplastic tumor. In a single pediatric case, ALT and ATRX loss developed in the anaplastic component only, and in another adult case, ALT was present in the PA‐A component only, but ATRX was not tested. Features associated with worse prognosis included subtotal resection, adult vs. pediatric, presence of a PA precursor preceding a diagnosis of anaplasia, necrosis, presence of ALT and ATRX expression loss. ALT and ATRX loss, as well as alterations involving the MAPK pathway, are frequent in PA with anaplasia at the time of development of anaplasia or in their precursors. Additionally, a small subset of PA with anaplasia have H3‐K27M mutations. These findings further support the concept that PA with anaplasia is a neoplasm with heterogeneous genetic features and alterations typical of both PA and diffuse gliomas. [ABSTRACT FROM AUTHOR]

Clinical classification of early dementia and mild cognitive impairment (MCI) is imprecise. We reported previously that molecular imaging classification of early dementia and MCI with dual amyloid and dopamine terminal positron emission tomography differs significantly from expert clinical classification. We now report pathological diagnoses in a substantial subset of our previously imaged subjects. Among 36 subjects coming to autopsy, imaging classifications and pathological diagnosis were concordant in 33 cases (κ = 0.85). This approach enhanced specificity of Alzheimer's disease diagnosis. The strong concordance of imaging-based classifications and pathological diagnoses suggests that this imaging approach will be useful in establishing more accurate and convenient classification biomarkers for dementia research. [ABSTRACT FROM AUTHOR]

Embryonal tumor with abundant neuropil and true rosettes ( ETANTR) is a recently described embryonal neoplasm of the central nervous system, consisting of a well-circumscribed embryonal tumor of infancy with mixed features of ependymoblastoma (multilayer ependymoblastic rosettes and pseudorosettes) and neuroblastoma (neuroblastic rosettes) in the presence of neuropil-like islands. We present the case of a young child with a very aggressive tumor that rapidly recurred after gross total resection, chemotherapy and radiation. Prominent vascular sclerosis and circumscribed tumor led to the diagnosis of malignant astroblastoma; however, rapid recurrence and progression of this large tumor after gross total resection prompted review of the original pathology. ETANTR is histologically distinct with focal glial fibrillary acid protein ( GFAP) and synaptophysin expression in the presence of neuronal and ependymoblastic rosettes with focal neuropil islands. These architectural features, combined with unique chromosome 19q13.42 amplification, confirmed the diagnosis. In this report, we describe tumor stem cell ( TSC) marker CD133, CD15 and nestin alterations in ETANTR before and after chemotherapy. We found that TSC marker CD133 was richly expressed after chemotherapy in recurrent ETANTR, while CD15 is depleted compared with that expressed in the original tumor, suggesting that CD133+ cells likely survived initial treatment, further contributing to formation of the recurrent tumor. [ABSTRACT FROM AUTHOR]

Recent work has identified novel point mutations in isocitrate dehydrogenase 1 ( IDH1) in the majority of the World Health Organization grades II and III infiltrative gliomas and secondary grade IV glioblastomas. Gangliogliomas consist of neoplastic ganglion and glial cells and, in contrast to infiltrative gliomas, are generally indolent. Yet distinguishing between a ganglioglioma and an infiltrative glioma with admixed gray matter can be difficult, perhaps accounting for some 'gangliogliomas' that ultimately show aggressive behavior. In this multi-institutional study, 98 cases originally diagnosed as ganglioglioma were analyzed for IDH1 mutations, 86 of which had follow-up data available. Eight cases (8.2%) were positive for R132H IDH1 mutations; six had silent IDH2 mutations and two had nonsense IDH2 mutations. The presence of mutant IDH1 in gangliogliomas correlated with a greater risk of recurrence ( P = 0.0007) and malignant transformation and/or death ( P < 0.0001) compared with tumors that were IDH1 wild type. Furthermore, the age of patients with IDH1-mutant gangliogliomas was higher than those without mutations (25.5 vs. 46.1 years, P = 0.0033). IDH1/2 testing of tumors suspected of being gangliogliomas may therefore be advisable, particularly in the adult population. [ABSTRACT FROM AUTHOR]

Introduction: Phosphoglycerate mutase deficiency (PGAM) is a rare metabolic myopathy that results in terminal block in glycogenolysis. Clinically, patients with PGAM deficiency are asymptomatic, except when they engage in brief, strenuous efforts, which may trigger myalgias, cramps, muscle necrosis, and myoglobinuria. An unusual pathologic feature of PGAM deficiency is the association with tubular aggregates. Methods: We report an African-American patient from Panama with partial deficiency of PGAM who presented with asymptomatic elevation of creatine kinase levels and tubular aggregates on muscle biopsy. Results: Muscle biopsies showed subsarcolemmal and sarcolemmal tubular aggregates in type 2 fibers. Muscle PGAM enzymatic activity was decreased and gene sequencing revealed a heterozygous mutation in codon 78 of exon 1 of the PGAM2 gene, which is located on the short arm of chromosome 7. Conclusions: PGAM deficiency has been reported in 14 patients, 9 of whom were of African-American ethnicity, and in 5 (36%) tubular aggregates were seen on muscle biopsy. Contrary to previously reported cases, our patient was initially asymptomatic. This further expands the PGAM deficiency phenotype. Muscle Nerve, 2013 [ABSTRACT FROM AUTHOR]