The differential diagnosis of pilocytic astrocytoma with atypical features and malignant glioma: an analysis of 16 cases with emphasis on distinguishing molecular features.

Rare pilocytic astrocytomas (PA) have atypical histologic and clinicoradiologic features that raise the differential diagnosis of glioblastoma. Whether ancillary studies can supplement histopathologic examination in placing these cases accurately on the spectrum of WHO Grade I PA to higher-grade glioma is not always clear, partly because these cases are not common. Here, ten PAs with atypical clinicoradiologic and histologic features and six pediatric glioblastoma multiforme (pGBMs) were analyzed for BRAF V600E, IDH1, IDH2, and TP53 mutations. Ki-67, p53, and p16 protein expression were also examined by immunohistochemistry. BRAF-KIAA1549 fusion status was assessed in the PA subgroup. The rate of BRAF-KIAA1549 fusion was high in these PAs (5/7 tumors) including four extracerebellar examples. A single BRAF V600E mutation was identified in the fusion-negative extracerebellar PA of a very young child who succumbed to the disease. TP53 mutations were present only in malignant gliomas, including three pGBMs and one case designated as PA with anaplastic features (with consultation opinion of pGBM). IDH1 and IDH2 were wild type in all cases, consistent with earlier findings that IDH mutations are not typical in high-grade gliomas of patients ≤14 years of age. Immunohistochemical studies showed substantial overlap in Ki-67 labeling indices, an imperfect correlation between p53 labeling and TP53 mutation status, and complete p16 loss in only two pGBMs but in no PAs. These results suggest that (a) BRAF-KIAA1549 fusion may be common in PAs with atypical clinicoradiologic and histologic features, including those at extracerebellar sites, (b) BRAF V600E mutation is uncommon in extracerebellar PAs, and (c) TP53 mutation analysis remains a valuable tool in identifying childhood gliomas that will likely behave in a malignant fashion.

Report of a young girl with MYH9 mutation and review of the literature.

MYH9 mutations cause the inherited macro-thrombocytopenic syndromes of May-Hegglin anomaly, Fechtner syndrome, Sebastian syndrome, and Epstein syndrome, collectively referred to as MYH9-related disease. We present the case of a girl with MYH9-related disease whose diagnosis was facilitated by platelet electron microscopy and MYH9 sequencing. We discuss our patient's clinical presentation, now with 12 years of follow-up. We also discuss management and her possible prognosis given her specific MYH9 mutation.

Molecular analysis of the AGL gene: identification of 25 novel mutations and evidence of genetic heterogeneity in patients with Glycogen Storage Disease Type III.

PURPOSE: Glycogen Storage Disease Type III (limit dextrinosis; Cori or Forbes disease) is an autosomal recessive disorder of glycogen metabolism caused by deficient activity of glycogen debranching enzyme in liver and muscle (Glycogen Storage Disease Type IIIa) or liver only (Glycogen Storage Disease Type IIIb). These two clinically distinct phenotypes are caused by mutations in the same gene (amylo-1,6-glucosidase or AGL). Although most patients with Glycogen Storage Disease Type III have private mutations, common mutations have been identified in some populations, and two specific mutations in exon 3, c.18_19delGA (p.Gln6HisfsX20) and c.16C>T (p.Gln6X), are associated with the Glycogen Storage Disease Type IIIb phenotype. METHODS: To further examine the heterogeneity found in Glycogen Storage Disease Type III patients, we have sequenced the AGL gene in 34 patients with a clinically and/or biochemically confirmed diagnosis of Glycogen Storage Disease Type III. RESULTS: We have identified 38 different mutations (25 novel and 13 previously reported) and have compiled a list of all mutations previously reported in the literature. DISCUSSION: We conclude that Glycogen Storage Disease Type III is a highly heterogeneous disorder usually requiring full gene sequencing to identify both pathogenic mutations. The finding of at least one of the two exon 3 mutations in all of the Glycogen Storage Disease Type IIIb patients tested allows for diagnosis of this subtype without the need for a muscle biopsy.

Histiocytic sarcoma arising in indolent small B-cell lymphoma: report of two cases with molecular/genetic evidence suggestive of a 'transdifferentiation' during the clonal evolution.

The biologic relationship between small B-cell lymphoma and histiocytic sarcoma (HS) when occurring in the same patient remains unclear, though recent data suggest a possible 'transdifferentiation' from follicular lymphoma (FL) to HS. We investigated the clonal relationship in two cases of small B-cell lymphoma with subsequent HS. Case 1: A 62-year-old female with splenic marginal zone lymphoma (SMZL) developed HS in a groin lymph node 1 year after the primary diagnosis. PCR/sequence analysis of the IGH gene showed a monoclonal rearrangement carrying an identical nucleotide sequence of PCR products from the spleen with SMZL and the lymph node with HS. Case 2: A 61-year-old female with a remote history of FL developed supraclavicular lymphadenopathy, which was confirmed to be HS. PCR analysis of the HS detected a monoclonal rearrangement of the IGH gene and FISH analysis revealed IGH/BCL2 fusion, a genetic hallmark for FL. The transformed HSs showed partial retention of their prior B-cell lymphomas' signatures, including expression of OCT2 in both cases and expression of BCL6 and enhanced expression of BCL2 in case 2. Both HSs demonstrated hypermutated IGH variable regions, arguing against a common progenitor mechanism of the transformation process. The data suggest a common clonal origin of B-cell lymphoma and subsequent HS occurring in the same patient, indicating that 'transdifferentiation' occurs in other small B-cell lymphomas, in addition to the previously reported FL or B-cell lymphoma with IGH/BCL2.