Acute lymphoblastic leukemia of childhood: identification of two distinct regions of deletion on the short arm of chromosome 12 in the region of TEL and KIP1

Cytogenetic analysis of acute lymphoblastic leukemia (ALL) of childhood identified nonrandom chromosomal abnormalities of the short arm of chromosome 12. The alterations include deletions that are thought to be indicative of the presence of a tumor suppressor gene that is mutated on the remaining allele. To refine further the chromosomal localization of this gene, we analyzed the loss of heterozygosity (LOH) of chromosome 12 in 100 primary ALL samples using 22 polymorphic markers and identified two distinct smallest common deleted regions on chromosome 12p13. One region is flanked by D12S77 and D12S98 and has a size of 4 cM. Twenty-six percent of informative patients showed LOH in this region. This region may contain the TEL gene. The other region is flanked by D12S269 and D12S308 including the KIP1 gene. Forty-four percent of informative patients showed LOH in this second region. Mutational analysis of KIP1 using polymerase chain reaction-single- strand conformation polymorphism analysis and Southern blot analysis showed no homozygous deletions and point mutations suggesting that the altered gene in this second region is not the KIP1. Clinical data showed that LOH of 12p was demonstrated more frequently in precursor-B ALLs (32 of 80; 40%) than in T-ALLs (1 of 20; 5%) (P = .0027). Furthermore, patients with 12p LOH were younger (P = .013), with a lower DNA index (P = .046), but they had the same survival rates at 3 years. In summary, these data suggest that two different tumor suppressor genes are on chromosome arm 12p, which act separately in the development of childhood precursor-B ALLs. One of the tumor suppressor genes is in the region the KIP1 gene, but our data suggest this gene is not abnormal. The other target is in the region of the TEL gene; and this candidate deserves further study.     

Fibrosarcoma Mimicking Plasmacytoma or Carcinoma: An Ultrastructural Study of 4 Cases

Because the fibroblast has a remarkable capability of phenotypic modulations, reflected in both morphologic and immunohistochemical (IHC) changes, ultrastructural studiesare mandatory to identify the variants of fibroblasts. Myofibroblasts or histiofibroblasts are such examples, demonstrating chimeric ultrastructural features of fibroblastic cells in common with smooth muscle cells or with histiocytes, respectively. The presence of epithelioid fibroblastic cells sharing morphologic features with epithelial or plasma cells has not been yet characterized. The authors identified 4 cases of fibrosarcomas (FS) characterized by an unusual phenotype and associated with peculiar ultrastructural findings. The electron microscopic (EM) findings were correlated with the histologic appearance and immunoprofile. All tumors were located in the extremities, 3 in soft tissues and 1 in the bone. By light microscopy 2 cases were composed predominantly by round uniform cells with a striking plasmacytoid appearance. One case mimicked carcinoma, composed predominantly by epithelioid cells and scattered giant tumor cells. The fourth case showed a mixture of plasmacytoid-like and epithelioid cells. By IHC, tumor cells were positive for vimentin and in 2 cases also for epithelial membrane antigen. Kappa/lambda light chain and cytokeratins markers were negative. By EM all 4 tumors showed in addition to classic features of fibroblasts, unusual epithelial-type features, such as secretory granules of "neurosecretory-type" (3 cases), rudimentary cell junctions (3 cases), microvilli (2 cases), and lumen-like structures (1 case). One plasmacytoid-type tumor showed finely granular extracellular deposits. The study describe 4 examples of fibrosarcomas with unusual features at the ultrastructural level, which are associated microscopically with a peculiar phenotype, mimicking plasmacytoma or carcinoma. These findings broaden the spectrum of fibroblastic cell variants in neoplasia.     

Spectrum of Low-Grade Fibrosarcomas: A Comparative Ultrastructural Analysis of Low-Grade Myxofibrosarcoma and Fibromyxoid Sarcoma

Low-grade fibrosarcomas have recently gained increasing attention in the literature, especially with the fall in popularity polls of the ubiquitous malignant fibrous histiocytoma (MFH). Firstly, most tumors previously known as myxoid MFH are labeled presently as myxofibrosarcomas. Secondly, the recognition and better understanding of a family of fibrosing-type fibrosarcoma, encompassing 3 members: fibromyxoid sarcoma (FMS), hyalinizing spindle cell tumor with giant rosettes (HSTGR), and sclerosing epithelioid fibrosarcoma (SEF). To expand further their understanding of the overlapping and distinct features of members included in the spectrum of low-grade fibrosarcoma, the authors carried out a comparative ultrastructural study among 15 low-grade myxofibrosarcomas (MFS) and 12 fibromyxoid sarcomas (FMS), after review of pathology and confirmation of diagnosis. The ultrastructural findings of the LG MFS identified spindle to plump cells, with abundant cytoplasm, rich in well-developed RER cisternae, often distended and sometimes cystically dilated, containing an electronlucent granular material. These results were in keeping with a well-differentiated fibroblastic-type cell phenotype. In addition, a less prominent cellular component included cells with RER, well-developed Golgi apparatus, lysosomes, and filopodia. These latter features define a fibroblastic variant with histiocytic-like properties, also known as histiofibroblasts. Myofibroblastic differentiation was quite limited and mostly absent in most of the cases. In summary, these findings recapitulate a similar spectrum with the cell constituents of so-called MFH. In contrast, the fine microscopic findings of the 12 FMS cases showed an inactive or more primitive form of fibroblastic type cells. The RER cisternae were generally underdeveloped, as expected for a generic fibroblastic-type proliferation. The cytoplasm was scant and showed a paucity of organelles, with the exception of abundant arrays of vimentin-type intermediate filaments. The very long, thin cell processes, sometimes associated with pinocytotic vesicles, were reminiscent of perineurioma ultrastructure.     

Metastatic Epithelioid Gastrointestinal Stromal Tumor: Yet Another Tumor with Anemone Cell Features

Since 1980 when Sibley and coworkers first described a nodal neoplasm of unknown histogenesis with striking surface microvilli for which they introduced the term "anemone cell," a series of reports have appeared in the literature illustrating tumors with similar ultrastructural features. While most reported cases showed differentiation along a particular line, rare cases remained histogenetically unclear. In this report a case is described of epithelioid gastric gastrointestinal stromal tumor metastatic to the liver, showing conspicuous long microvillus-type cell processes partially or circumferentially coating the cell surfaces, thus qualifying as yet another tumor type with anemone cell features.     

Novel MIR143‐NOTCH fusions in benign and malignant glomus tumors

Glomus tumors (GT) have been classified among tumors of perivascular smooth muscle differentiation, together with myopericytoma, myofibroma/tosis, and angioleiomyoma, based on their morphologic overlap. However, no molecular studies have been carried out to date to investigate their genetic phenotype and to confirm their shared pathogenesis. RNA sequencing was performed in three index cases (GT1, malignant GT; GT2, benign GT and M1, multifocal myopericytoma), followed by FusionSeq data analysis, a modular computational tool developed to discover gene fusions from paired‐end RNA‐seq data. A gene fusion involving MIR143 in band 5q32 was identified in both GTs with either NOTCH2 in 1p13 in GT1 or NOTCH1 in 9q34 in GT2, but none in M1. After being validated by FISH and RT‐PCR, these abnormalities were screened on 33 GTs, 6 myopericytomas, 9 myofibroma/toses, 18 angioleiomyomas and in a control group of 5 sino‐nasal hemangiopericytomas. Overall NOTCH2 gene rearrangements were identified in 52% of GT, including all malignant cases and one NF1‐related GT. No additional cases showed NOTCH1 rearrangement. As NOTCH3 shares similar functions with NOTCH2 in regulating vascular smooth muscle development, the study group was also investigated for abnormalities in this gene by FISH. Indeed, NOTCH3 rearrangements were identified in 9% of GTs, all present in benign soft tissue GT, one case being fused to MIR143. Only 1/18 angioleiomyomas showed NOTCH2 gene rearrangement, while all the myopericytomas and myofibroma/toses were negative. In summary, we describe novel NOTCH1–3 rearrangements in benign and malignant, visceral, and soft tissue GTs. © 2013 Wiley Periodicals, Inc.