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K Zakrzewski

Publications and source records attributed to K Zakrzewski.

64 records · Page 4Linked to original sources
PubMedDate not supplied

Dysembryoplastic neuroectodermal tumor: an ultrastructural study of six cases.

Dysembryoplastic neuroectodermal tumor (DNT) is a rare brain neoplasm. Although the tumor pathology is relatively well charactererized, its full clinicopathological spectrum is still discussed, and ultrastructural data on it are very limited. Here, the authors describe detailed ultrastructural pathology of 7 cases of DNT. Each tumor consisted of 3 major elements: neoplastic cells (oligodendroglial-like cells, OLC), elongated processes forming neuropil-like structure, and expanded "mucoid" extracellular space, the latter giving an impression of cellular elements floating within it. Neoplastic cells had round, oval, or elongated nuclei, no discernible nucleoli, and a relatively narrow rim of cytoplasm. Some nuclei were irregular and invaginated, and pseudoinclusions (invaginations of cytoplasm penetrated into toroid-like nuclear formations) were observed. Part of the cytoplasm sequestrated within pseudoinclusions often appeared degenerated with large blebs and electron-lucent vesicles, and some of these contained, in turn, semicircular profiles of unknown significance. Chromatin was clustered below the nuclear membrane. The cytoplasm contained a few mitochondria, round rather than elongated, a few stacks of rough endoplasmic reticulum, and scanty microtubules and clear vesicles. The second element consisted of innumerable cellular processes. Some of these were elongated and formed stacks connected by symmetric or asymetric adhesive plaque junctions. Others had shorter "neck" containing microtubules extending into bulbous extensions. Dense-cored vesicles were occasionally observed, both in the cytoplasm of neoplastic cells and within processes. In one cell, cross-sectioned annulate lamellae were found. In the cytoplasm of a few cells, unusual inclusions reminiscent of ribosome-lamellae resembled "laboratory tubes" with cone-like endings. At higher power, walls of the "tubes" resolved into layered structures composed of several laminae; between these, ribosome-like structures were visible. The authors conclude that OLC exhibit clear-cut characteristics of neuronal cells and not true oligodendocytes.

Adolescent↗
PubMedDate not supplied

Primitive neuroectodermal tumors: ultrastructural and immunohistochemical studies.

We report here ultrastructural and immunohistochemical studies of neuroblastic differentiation in the retrospective (n = 17) and prospective (n = 26) series of primitive neuroectodermal tumors (PNETs). By electron microscopy, neuritelike structures containing parallel-oriented microtubules, adhesive plaque junctions, and pleomorphic dense-core vesicles were found in the majority of tumor specimens while synaptic specializations were very rare. By immunohistochemistry, synaptophysin appeared to be the most reliable marker for neuroblastic differentiation present in the most reliable marker for neuroblastic differentiation present in the majority of tumors, while 200 kDa neurofilament protein was immunovisualized in a lower proportion of tumors. Glial fibrillary acidic protein (GFAP) was expressed in both reactive astrocytes and in a small proportion of otherwise typical neoplastic cells. We conclude that the majority of PNETs revealed diverse differentiation and that electron microscopy is still the most reliable tool for its detection followed by immunohistochemistry for synaptophysin.

Adolescent↗
PubMedDate not supplied

Microsatellite instability and expression of DNA mismatch repair genes in malignant astrocytic tumors from adult and pediatric patients.

Microsatellite instability (MSI) is used as a molecular marker for defective DNA mismatch repair (MMR) genes. We report here alterations of MSI in 15 malignant astrocytomas (WHO grade III) and glioblastomas (GBM; WHO grade IV) of pediatric patients (2 - 21 years) and 12 GBM from adults (44 - 68 years) by comparative analysis of BAT25/BAT26 loci and 10 other microsatellite markers. High-level microsatellite instability (MSI-H) occurred in 4 of the 15 pediatric cases (26.7%) and in 1 of the 12 adult GBM cases (8.3%). Low-level microsatellite instability (MSI-L) was observed in 6 pediatric cases (40%) and 8 adult GBM (66.7%). Unstable BAT-25 locus was found in 1 of the MSI-H pediatric cases. Thus, 2 unstable cases showed no instability of this marker. For BAT-26, such a discordance was even more profound: in 1 of MSI-H cases, we obtained no PCR product and the remaining 3 showed no alterations of this marker. MSH2 (Human MutS, Homologue2) protein was detected in all but 3 pediatric cases (1 highly unstable and 2 low-level unstable) and in all adult cases. MLH1 (Human MutL, Homologue 1) protein was detected in all but 2 pediatric cases (1 highly unstable and 1 low-level unstable). Thus, 2 highly unstable pediatric cases showed no detectable MLH1/MSH2 proteins. Our data support earlier observations that MSI occurs predominantly in malignant astrocytic tumors of young patients, which lends support to the hypothesis of different molecular mechanisms of pediatric brain tumors. Surprisingly, we found no significant correlation between the status of 10 microsatellite markers and that of either BAT25 or BAT26 loci or with the expression of MMR genes.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

Molecular abnormalities in pediatric embryonal brain tumors--analysis of loss of heterozygosity on chromosomes 1, 5, 9, 10, 11, 16, 17 and 22.

Embryonal tumors, the most common group of malignant brain tumors in childhood, are heterogeneous and have been associated with a large number of genetic abnormalities. The aim of this study was to comprehensively analyze loss of heterozygosity (LOH) on regions harboring suppressor genes (PTCH2, PTCH1, APC, PTEN, DMBT1, SUFU, AXIN1, hSNF5/INI1) and to study chromosomal regions in which deletions have been described most frequently (1p, 1q, 11p, 16p, 17p). Twenty-nine children (17 male and 12 female), aged from 1 year 13 years were included in this study. There were 24 medulloblastomas (MB) and 5 supratentorial primitive neuroectodermal tumors (sPNET). Tissue samples from 29 primary and 11 recurrent tumors were analyzed according to the LOH standard procedures, which were extended to include fluorescence in situ hybridization for detection of isochromosome 17q (i(17q)) and direct sequencing ofTP53 exon 4. LOH on 17p was found in 15 out of 29 tumors. FISH analysis identified the presence of i(17q) in 16 tumors. Comparison of LOH analysis and the FISH data indicated that alterations of 17p were related to be the introduction of an i(17q) formation. LOH on 10q and 9q was observed in 4 and 2 cases, respectively, and was associated with alterations of chromosome 17. These results indicated a connection between alterations of PTCH/SHH genes and abnormalities of chromosome 17. A deleted region on 22q, covering the hSNF5/INI1 locus, was observed in 3 tumors. Progression of the molecular changes occurred in 1 case of recurrent medulloblastoma. LOH on 10q and 17p was found in both primary and recurrent tumor, while losses on 11p, 16p, and 16q occurred only in the recurrent tumor. No evidence of alteration in TP53 exon 4 was identified.

Adolescent↗