Background Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) is a mitochondrial cytopathy caused by mutations in mitochondrial DNA. Clinical manifestation is typically before the age of 40. Case presentation We present the case of a 63-year-old female in whom the symptoms of MELAS were initially misdiagnosed as episodes of recurrent ischemic strokes. Brain imaging including MRI, clinical and laboratory findings that lent cues to the diagnosis of MELAS are discussed. In addition, MRI findings in MELAS in comparison to imaging mimics of MELAS are presented. Conclusions This case underscores the importance of considering MELAS as a potential cause of recurrent stroke-like events if imaging findings are untypical for cerebral infarction, even among middle-aged patients with vascular risk factors.

Fibroepithelial lesions (FL) of the breast, in particular, phyllodes tumors (PT) and fibroadenomas, pose a significant diagnostic challenge. There are no generally accepted criteria that distinguish benign, borderline, malignant PT and fibroadenomas. Combined genome-wide DNA methylation and copy number variant (CNV) profiling is an emerging strategy to classify tumors. We compiled a series of patient-derived archival biopsy specimens reflecting the FL spectrum and histological mimickers including clinical follow-up data. DNA methylation and CNVs were determined by well-established microarrays. Comparison of the patterns with a pan-cancer dataset assembled from public resources including “The Cancer Genome Atlas” (TCGA) and “Gene Expression Omnibus” (GEO) suggests that FLs form a methylation class distinct from both control breast tissue as well as common breast cancers. Complex CNVs were enriched in clinically aggressive FLs. Subsequent fluorescence in situ hybridization (FISH) analysis detected respective aberrations in the neoplastic mesenchymal component of FLs only, confirming that the epithelial component is non-neoplastic. Of note, our approach could lead to the elimination of the diagnostically problematic category of borderline PT and allow for optimized prognostic patient stratification. Furthermore, the identified recurrent genomic aberrations such as 1q gains (including MDM4), CDKN2a/b deletions, and EGFR amplifications may inform therapeutic decision-making.

NUT midline carcinoma is an aggressive neoplasm defined by chromosomal rearrangements of the nuclear protein in testis (NUT) gene ( NUTM1 ). In this article, we present a strategy to detect this rare tumor through a standard DNA methylation array analysis even when occurring in unusual anatomic sites. We illustrate our approach through a case study in which we detected metastatic spread of a NUT midline carcinoma within a bone marrow biopsy that exhibited histological features of a blastoid, undifferentiated neoplasm. Our strategy builds on molecular data derived from The Cancer Genome Atlas and Gene Expression Omnibus as well as computational strategies adopted from the Brain Tumor Methylation Classifier. It is a combined approach that detects the unusual cell lineage of NUT midline carcinomas and makes diagnostic use of the entity-specific copy number alterations. Electronic supplementary material The online version of this article (10.1007/s00428-020-02869-7) contains supplementary material, which is available to authorized users.

Unresectable neuroendocrine neoplasms (NENs) often poorly respond to standard therapeutic approaches. Alkylating agents, in particular temozolomide, commonly used to treat high-grade brain tumors including glioblastomas, have recently been tested in advanced or metastatic NENs, where they showed promising response rates. In glioblastomas, prediction of response to temozolomide is based on the assessment of the methylation status of the MGMT gene, as its product, O-6-methylguanine-DNA methyltransferase, may counteract the damaging effects of the alkylating agent. However, in NENs, such a biomarker has not been validated yet. Thus, we have investigated MGMT methylation in 42 NENs of different grades and from various sites of origin by two different approaches: in contrast to methylation-specific PCR (MSP), which is commonly used in glioblastoma management, amplicon bisulfite sequencing (ABS) is based on high resolution next-generation sequencing and interrogates several additional CpG sites compared to those covered by MSP. Overall, we found MGMT methylation in 74% (31/42) of the NENs investigated. A higher methylation degree was observed in well-differentiated tumors and in tumors originating in the gastrointestinal tract. Comparing MSP and ABS results, we demonstrate that the region analyzed by the MSP test is sufficiently informative of the MGMT methylation status in NENs, suggesting that this predictive parameter could routinely be interrogated also in NENs

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Large cell carcinomas with rhabdoid phenotype (LCC-RP) account for <1% of pulmonary large cell carcinomas and are associated with extremely poor prognosis. We report a case of a 64-year-old male patient who presented at an advanced stage with a LCC-RP, arising from a poorly differentiated adenocarcinoma of the lung. Ninety percent of the tumor consisted of large pleomorphic rhabdoid tumor cells that showed eosinophilic cytoplasmic inclusions and the remaining 10% showed evidence of adenomatous differentiation. Rhabdoid areas were immunohistochemically positive for pan-cytokeratin AE1/3, epithelial membrane antigen, vimentin, thyroid transcription factor-1, integrase interactor-1, and negative for desmin. Nuclear positivity was absent for Myo-D1. The parent adenocarcinoma was positive for thyroid transcription factor-1 and cytokeratins 7. Epidermal growth factor receptor mutation analysis revealed the same mutation (p.delL747-T751) in both areas, suggesting that the malignant rhabdoid phenotype represents a dedifferentiation phenomenon of the adenocarcinoma. This is the first reported case of an Exon 19 deletion in epidermal growth factor receptor of the activating type detected in a LCC-RP associated with a poorly differentiated pulmonary adenocarcinoma.

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