SEARCH · Search PubMed

Results for “Polyploidy”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources

PubMed1986

Microspectrofluorometric Measurement of Chloroplast DNA in Dividing and Expanding Leaf Cells of Spinacia oleracea.

Absolute DNA amounts of individual chloroplasts from mesophyll and epidermal cells of developing spinach leaves were measured by microspectrofluorometry using the DNA-specific stain, 4,6-diamidino-2-phenyl indole, and the bacterium, Pediococcus damnosus, as an internal standard. Values obtained by this method showed that DNA amounts of individual chloroplasts from mesophyll cells fell within a normal distribution curve, although mean DNA amounts changed during leaf development and also differed from the levels in epidermal chloroplasts. There was no evidence in the data of plastids containing either the high or low levels of DNA which would be indicative of discontinuous polyploidy of plastids, or of division occurring in only a small subpopulation of chloroplasts. By contrast, the distribution of nuclear DNA amounts in the same leaf tissues in which cell division was known to be occurring showed a clear bimodal distribution. We consider that the distribution of chloroplast DNA in the plastid population shows that there is no S-phase of chloroplast DNA synthesis, all chloroplasts in the population in young leaf cells synthesize DNA, and all chloroplasts divide.

Journal Article↗

PubMed1987

Photosynthesis, Leaf Anatomy, and Cellular Constituents in the Polyploid C(4) Grass Panicum virgatum.

Photosynthetic gas exchange, activities of six key C(4) cycle enzymes, amounts of soluble protein, chlorophyll, and DNA, and various leaf anatomical and structural features were measured in naturally occurring tetraploid and octaploid plants of the NAD-malic enzyme type C(4) grass Panicum virgatum L. On a leaf area basis, the photosynthetic rate and concentrations of DNA, soluble protein, and chlorophyll were 40 to 50% higher, and enzyme activities 20 to 70% higher in the octaploid than in the tetraploid. Photosynthetic cells in the octaploid were only 17 to 19% larger in volume, yet contained 33 to 38% more chloroplasts than cells in the tetraploid. On a per cell basis the contents of DNA, soluble protein, and chlorophyll, activities of carboxylating photosynthetic enzymes, and carbon assimilation rate were all doubled in octaploid compared with tetraploid cells. Since cellular volume did not double with genome doubling, cellular constituents were more concentrated in the cells of the octaploid. The influences of polyploidy were balanced between mesophyll and bundle sheath cells since the changes in physical and biochemical parameters with ploidy level were similar in both cell types. We conclude that photosynthetic activity in these two polyploid genotypes of P. virgatum is determined by enzyme activities and concentrations of biochemical constituents, and that selection for smaller cell volume has led to higher photosynthetic rates per unit leaf area in the octaploid. The ratio of DNA content to cellular volume is a major factor determining the concentrations of gene products in cells. The number of chloroplasts, however, is controlled more by cellular volume than by the number of nuclear chromosomes.

Journal Article↗

PubMed2006

Sequence-level analysis of the diploidization process in the triplicated FLOWERING LOCUS C region of Brassica rapa.

Strong evidence exists for polyploidy having occurred during the evolution of the tribe Brassiceae. We show evidence for the dynamic and ongoing diploidization process by comparative analysis of the sequences of four paralogous Brassica rapa BAC clones and the homologous 124-kb segment of Arabidopsis thaliana chromosome 5. We estimated the times since divergence of the paralogous and homologous lineages. The three paralogous subgenomes of B. rapa triplicated 13 to 17 million years ago (MYA), very soon after the Arabidopsis and Brassica divergence occurred at 17 to 18 MYA. In addition, a pair of BACs represents a more recent segmental duplication, which occurred approximately 0.8 MYA, and provides an exception to the general expectation of three paralogous segments within the B. rapa genome. The Brassica genome segments show extensive interspersed gene loss relative to the inferred structure of the ancestral genome, whereas the Arabidopsis genome segment appears little changed. Representatives of all 32 genes in the Arabidopsis genome segment are represented in Brassica, but the hexaploid complement of 96 has been reduced to 54 in the three subgenomes, with compression of the genomic region lengths they occupy to between 52 and 110 kb. The gene content of the recently duplicated B. rapa genome segments is identical, but intergenic sequences differ.

Brassica rapa↗

PubMed1993

Relationship between Endopolyploidy and Cell Size in Epidermal Tissue of Arabidopsis.

Relative quantities of DNA in individual nuclei of stem and leaf epidermal cells of Arabidopsis were measured microspectrofluorometrically using epidermal peels. The relative ploidy level in each nucleus was assessed by comparison to root tip mitotic nuclei. A clear pattern of regular endopolyploidy is evident in epidermal cells. Guard cell nuclei contain levels of DNA comparable to dividing root cells, the 2C level (i.e., one unreplicated copy of the nuclear DNA). Leaf trichome nuclei had elevated ploidy levels of 4C, 8C, 16C, 32C, and 64C, and their cytology suggested that the polyploidy represents a form of polyteny. The nuclei of epidermal pavement cells were 2C, 4C, and 8C in stem epidermis, and 2C, 4C, 8C, and 16C in leaf epidermis. Morphometry of epidermal pavement cells revealed a direct proportionality between nuclear DNA level and cell size. A consideration of the development process suggests that the cells of highest ploidy level are developmentally oldest; consequently, the developmental pattern of epidermal tissues can be read from the ploidy pattern of the cells. This observation is relevant to theories of stomate spacing and offers opportunities for genetic analysis of the endopolyploidy/polyteny phenomenon.

Journal Article↗

PubMed1986

Growth factor and cytogenetic abnormalities in cultured nevi and malignant melanomas.

It has been proposed that benign nevi that fail to differentiate normally may undergo stepwise growth and morphologic changes resulting in progression toward dysplastic nevi, which in some cases progress into malignant melanoma. In this study, we sought to determine the relationship between production of endogenous growth factors and the appearance of chromosomal abnormalities in cultured nevi and melanomas. Newly established cultures from 8 nevi with benign histology and 6 malignant melanomas, and 2 malignant melanoma cell lines were studied. Assays for mitogenic growth factors were based on stimulation of [3H]thymidine incorporation into DNA in Hs0294 malignant melanoma cells, produced by serum-free conditioned medium from nevus or melanoma cultures. Karyotypes were examined in cultures of an equivalent passage. Three of the 8 nevus cultures were mitogen-negative and displayed normal karyotypes; one nevus culture was mitogen-positive and had a normal karyotype, although the biopsied tissue demonstrated histologic evidence of benign melanocytic proliferation; one was mitogen-negative initially, but had an extra chromosome 8 in 2 of 50 cells; 3 were mitogen-positive and chromosomally abnormal. Each of the cultures in this latter group exhibited reciprocal translocation (rcpt) as the only identifiable abnormality [rcpt(6;15), rcpt(10;15), rcpt(15;20)], or a constitutional rcpt(4;5). Thus, there was direct correlation between growth factor production and chromosome abnormality in 6 of 8 benign nevus cultures. In the newly established melanoma cultures there was also concordance between growth factor and chromosomal status; conditioned media from 4 of 6 were mitogen-positive by at least one assay, and all 4 of the mitogen-positive cultures had chromosomally abnormal cell populations. Of the 2 melanoma cultures negative for growth factors, one was also negative for chromosome abnormality; the other had chromosomal change consisting of increased polyploidy. Both melanoma cell lines had abnormal karyotypes and were mitogen-positive. Though numerous chromosome changes were noted in the karyotypically abnormal melanoma cells, 6 of the 8 cultures exhibited abnormalities in chromosomes 1, 6, and/or 7. These data suggest that steps in the progression from benign nevi toward dysplastic nevi or malignant melanoma include: proliferation resulting from altered production of endogenous mitogenic growth factors; and development of specific chromosomal abnormalities.

Cells, Cultured↗

PubMed2002

Single mutations silence PGiC2 genes in two very recent allotetraploid species of Clarkia.

Our understanding of how polyploidy influences gene evolution is limited by the fact there have been few molecular descriptions of particular genes and their expression in polyploid plants and their diploid progenitors. Here we use evidence from sequencing of genomic DNA and cDNA obtained by reverse transcriptase-polymerase chain reaction and 3' rapid amplification of cDNA ends to describe PgiC genes and their expression in two allotetraploid species of the wildflower genus Clarkia, C. delicata and C. similis. PgiC encodes the cytosolic isozyme of phosphoglucose isomerase (EC 5.3.1.9) and was duplicated in the ancestral stock of Clarkia, giving rise to paralogous genes PgiC1 and PgiC2. The active form of the PGIC enzyme is a dimer of like subunits. The electrophoretic patterns in the parent species show three bands of activity, representing two homodimers and a heterodimer of intermediate mobility, and are encoded by two genes. The electrophoretic patterns in the tetraploids also show three bands, but the tetraploids were expected to have multiple PGIC isozymes encoded by four genes. Our molecular studies demonstrated that each tetraploid has two PgiC1 and two PgiC2 genes, as predicted. One gene in each of them has been silenced by a single mutation, and a functional protein is no longer produced. In C. similis, PgiC2(mod) was silenced by a mutation of a single nucleotide in exon 5 that created a stop codon. In C. delicata, a polymorphism exists between a normal allele and a defective allele of PgiC2(epi) that has a deletion of a splice junction in intron 19 that results in the synthesis of a transcript lacking an entire exon, an example of exon skipping. The three-banded PGIC electrophoretic pattern of both tetraploid species arises because isozymes encoded by two or three of the genes comigrate. A very recent origin for both tetraploids is suggested by the near identity of several of their PgiC genes to their corresponding diploid orthologues and the absence of any acceleration in mutation rates. The problem of assessing genetic redundancy in tetraploids is discussed.

Clarkia↗

PubMed2004

Developmental success, stability, and plasticity in closely related parthenogenetic and sexual lizards (Heteronotia, Gekkonidae).

The developmental trajectory of an organism is influenced by the interaction between its genes and the environment in which it develops. For example, the phenotypic traits of a hatchling reptile can be influenced by the organism's genotype, by incubation temperature, and by genetically coded norms of reaction for thermally labile traits. The evolution of parthenogenesis provides a unique opportunity to explore such effects: a hybrid origin of this trait in vertebrates modifies important aspects of the genotype (e.g., heterozygosity, polyploidy) and may thus impact not only on the phenotype generally, but also on the ways in which incubation temperature affects expression of the phenotype. The scarcity of vertebrate parthenogenesis has been attributed to developmental disruptions, but previous work has rarely considered reaction norms of embryogenesis in this respect. We used closely related sexual and asexual races of the Australian gecko Heteronotia binoei, which include those with multiple origins of parthenogenesis, to explore the ways in which reproductive modes (sexual, asexual), incubation temperatures (24, 27, and 30 degrees C), and the interaction between these factors affected hatchling phenotypes. The hatchling traits we considered included incubation period, incidence of deformities, hatchling survivorship, body size and shape, scalation (including fluctuating asymmetry), locomotor performance, and growth rate. Developmental success was slightly reduced (higher proportion of abnormal offspring) in parthenogenetic lineages although there was no major difference in hatching success. Incubation temperature affected a suite of traits including incubation period, tail length, body mass relative to egg mass, labial scale counts, running speed, growth rate, and hatchling survival. Our data also reveal an interaction between reproductive modes and thermal regimes, with the phenotypic traits of parthenogenetic lizards less sensitive to incubation temperature than was the case for their sexual relatives. Thus, the evolution of asexual reproduction in this species complex has modified both mean hatchling viability and the norms of reaction linking hatchling phenotypes to incubation temperature. Discussions on the reasons why parthenogenetic organisms are scarce in nature should take into account interactive effects such as these; future work could usefully try to tease apart the roles of parthenogenesis, its hybrid origin (and thus effects on ploidy and heterozygosity, etc.), and clonal selection in generating these divergent embryonic responses.

Analysis of Variance↗

PubMed1990

Antitumor activities of IKP-104, a 4(1H)-pyrizinone derivative, on cultured and implanted tumors.

Antitumor activities of IKP-104, a 4(1H)-pyrizinone derivative, were investigated with cultured tumor cell lines and implanted tumors in mice. IKP-104 inhibited the growth of cultured murine tumor cell lines (L1210 leukemia, Lewis lung carcinoma and B16 melanoma) and human tumor cell lines (K562 leukemia and HeLa cervical carcinoma). It also had antitumor effects on implanted murine ascitic tumors (L1210 leukemia and sarcoma 180) and a murine solid tumor (Lewis lung carcinoma). IKP-104 could be classified as a phase-dependent cytostatic drug based on the mode of growth inhibition of cultured B16 melanoma cells compared with those of several other antitumor agents. The effect of IKP-104 on the cell cycle traverse of cultured B16 melanoma cells was estimated by morphological and flow cytometric analyses. Cells accumulated in the mitotic phase, and abortive mitosis or polyploidy or multinucleation was induced from 6 h after exposure to IKP-104. Based on these results, IKP-104 is expected to be useful for the treatment of tumors, and its mode of action seemed to be similar to that of metaphase arrestants such as colchicine or vinca alkaloids.

Animals↗

PubMed1982

A comparative investigation of the antimitotic action of 2-mercaptoethanol and colcemid on V-79 Chinese hamster cells.

The current study was performed to characterize the antimitotic action of 2-mercaptoethanol (MET) on mammalian cells. At concentrations of 2.5 x 10(-2) m, MET arrests V-79 Chinese hamster cells in metaphase. Smaller concentrations (from 5 x 10(-3) m) only produce a mitotic block after several hours, only arresting those mitoses which have gone through one cell cycle in the presence of MET. The accumulation of mitoses by MET is smaller in comparison with colcemid, explained by an effect reducing the number of cells which enter mitosis. In contrast to colcemid, MET-concentrations which do not lead to a mitotic block cause a delay in proliferation. It was shown, by means of the BUdR-labelling method that cells in the presence of colcemid concentrations which arrest mitosis again enter interphase and become polyploid, whereas MET leads to an irreversible arrest of mitosis and does not produce polyploidy in V-79 cells.

Animals↗

PubMed2007

Generation of somatic cell hybrids for the production of biologically active factors that stimulate proliferation of other cells.

OBJECTIVE: Some normal somatic cells in culture divide a limited number of times before entering a non-dividing state called replicative senescence and fusion of normal cells with immortal cells claimed to produce hybrid cells of limited proliferation. We reinvestigated the proliferative capacity of hybrid cells between normal cell and immortal cell. MATERIALS AND METHODS: Normal pig fibroblast cells and cells of immortal mouse fibroblast cell line F7, a derivative of GM05267, were fused by polyethylene glycol treatment and subsequently the fused cells were cultured in a selective medium containing hypoxanthine-aminopterin-thymidine in order to enrich the hybrid cells. The hybrid cells were then monitored for chromosome content and proliferation. RESULTS: Cytogenetic analysis revealed that the hybrid cells contained polyploidy chromosomes derived from normal pig fibroblasts. These hybrid cells exhibit no sign of replicative senescence after more than 190 population doublings in vitro. Instead, these hybrid cells have an accelerated growth and proliferate even in the complete absence of glutamine. In addition, these hybrids produce biologically active factors in the conditioned media, which not only can accelerate their own proliferation but also can reinitiate mitotic activity in the senescent-like normal fibroblast cells. CONCLUSIONS: Our results question the validity of cellular senescence as a dominant trait. Additionally, the generation of hybrid cells using the specific mouse cell line can be applied to the generation of hybrids with other normal cell types and can be used to produce tissue-specific growth-factor(s) to extend the lifespan and/or improve the proliferation of various normal cells, including adult stem cells.

Animals↗

PubMed1995

Complete hydatidiform mole in twin pregnancy: differentiation from partial mole with interphase cytogenetic and DNA cytometric analyses on paraffin embedded tissues.

Six cases of hydatidiform mole associated with normal chorionic villi and a normal embryo/fetus (in five cases) were investigated with interphase cytogenetic and DNA cytometric analyses for diagnostic purposes. DNA probes specific for the pericentromeric regions of chromosomes 1 and X and for the long arm of chromosome Y were used. In four cases a dizygotic twin pregnancy could be proven. In these cases, the histologically normal chorionic villi showed an XY DNA-diploid pattern, consistent with a normal male conceptus, and the molar chorionic villi a XX pattern. In the other two cases an identical sex chromosomal pattern was found in the normal and in the molar villi (XX/XX and XY/XY respectively). In all six cases the molar placental tissues showed prominent trophoblastic hyperplasia with DNA-polyploidy, consistent with a complete hydatidiform mole. In two cases persistent gestational trophoblastic disease developed. It is emphasized that twin pregnancies composed of a normal conceptus and a complete mole have a relatively high risk for the development of persistent trophoblastic disease and therefore, should be carefully differentiated from triploid partial moles with a relatively low risk of persistent gestational trophoblastic disease. These case reports indicate that additional interphase cytogenetic and DNA cytometric analyses are useful in this differential diagnosis.

Adult↗

PubMed1995

Mitochondrial DNA diversity in an apomictic Daphnia complex from the Canadian high arctic.

Cyclic parthenogenesis is the ancestral mode of reproduction in the cladoceran crustacean, Daphnia pulex, but some populations have made the transition to obligate parthenogenesis and this is the only mode of reproduction known to occur in arctic populations. Melanism and polyploidy are also common in arctic populations of this species. Prior allozyme studies of arctic D. pulex revealed substantial levels of clonal diversity on a regional scale. Clonal groupings based on cluster analysis of allozyme genotypes do not conform to groupings based on the presence/absence of melanin or on ploidy level. In order to further elucidate genetic relationships among arctic D. pulex clones, mitochondrial DNA (mtDNA) variation was examined in 31 populations from two Canadian high-arctic sites. The data were also compared to a previous study of mtDNA variation in populations from a Canadian low-arctic site. Cladistic analysis of restriction site variation of the entire mitochondrial genome and nucleotide sequence variation of the mitochondrial control region was used to construct genetic relationships among mitochondrial genotypes. Three distinct mitochondrial lineages were detected. One lineage was associated with diploid, nonmelanic clones and is the same as the lineage that is found in temperate populations of D. pulex. The other two lineages (A & B) were associated with polyploid, melanic clones. Sequence divergence between the A and B lineages was 2.4%. Sequence divergence between D. pulex and either of these two lineages exceeded 3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

Geographic and phylogenetic evidence for dispersed nuclear introgression in a daphniid with sexual propagules.

The role of among-species gene flow in eukaryotic evolution remains controversial. Putative hybrid lineages are common in water fleas, but their ecological success is often associated with polyploidy and the production of asexual propagules. Advanced hybrid lineages with sexual propagules are expected to be geographically restricted because their successful dispersal is contingent on overcoming fertility complications, assimilation by parent taxa, and competition with parent taxa. Here we provide evidence that a diploid lineage of Daphnia has been formed by introgression between distantly related species and attained a broad distribution (Nearctic) despite its requirement for sexual propagules. The evidence is based on geographical discordance, phylogenetic discordance, recombinant genotypes and additive genotypes of the nuclear internal transcribed spacer regions (ITS) and mitochondrial DNA. Additive genotypes also provided evidence of hybridization between introduced European Daphnia and North American Daphnia. We argue that the unique biology of Holarctic lacustrine water fleas and the spatial separation of lineages during Pleistocene glaciation have promoted hybridization and its evolutionary consequences.

Animals↗

PubMed2006

European colonization by the spined loach (Cobitis taenia) from Ponto-Caspian refugia based on mitochondrial DNA variation.

In the last 20 years, new species, asexual reproduction, polyploidy and hybridization have all been reported within the genus Cobitis. An understanding of the current distribution and baseline phylogeographical history of 'true' nonhybrid Cobitis species is crucial in order to unravel these discoveries. In the present work, we investigated the phylogeography of the spined loach, Cobitis taenia, using 1126 bp of the mitochondrial cytochrome b gene from 174 individuals collected at 47 sites. In total, 51 haplotypes that differed at 49 positions (4.35%) were detected. We deduce that C. taenia survived European glaciations in at least three refugees in the Ponto-Caspian area. Two of these refugees each provided a major lineage that recolonized Europe in separate directions: one westward to England and the other spreading north into Russia before moving west. A third (minor) lineage that contributed little to the recolonization of Europe was also revealed--remaining near its Black Sea refuge. However, more recent history was difficult to resolve with colonization from a more western refugium during the last glacial maximum (LGM) a distinct possibility. Nested clade analysis indicates a pattern of restricted gene flow with isolation by distance at the first two levels and overall. Unlike many other European freshwater fish species, the Danube is not part of the current distribution of C. taenia, nor was it used as either a refuge or a source of colonization of Europe. Low genetic diversity within C. taenia suggests that its colonization of Europe is relatively recent. Demographic analyses revealed a history of recent expansion and isolation by distance.

Animals↗

PubMed2006

Comparative genomics and repetitive sequence divergence in the species of diploid Nicotiana section Alatae.

Combining phylogenetic reconstructions of species relationships with comparative genomic approaches is a powerful way to decipher evolutionary events associated with genome divergence. Here, we reconstruct the history of karyotype and tandem repeat evolution in species of diploid Nicotiana section Alatae. By analysis of plastid DNA, we resolved two clades with high bootstrap support, one containing N. alata, N. langsdorffii, N. forgetiana and N. bonariensis (called the n = 9 group) and another containing N. plumbaginifolia and N. longiflora (called the n = 10 group). Despite little plastid DNA sequence divergence, we observed, via fluorescent in situ hybridization, substantial chromosomal repatterning, including altered chromosome numbers, structure and distribution of repeats. Effort was focussed on 35S and 5S nuclear ribosomal DNA (rDNA) and the HRS60 satellite family of tandem repeats comprising the elements HRS60, NP3R and NP4R. We compared divergence of these repeats in diploids and polyploids of Nicotiana. There are dramatic shifts in the distribution of the satellite repeats and complete replacement of intergenic spacers (IGSs) of 35S rDNA associated with divergence of the species in section Alatae. We suggest that sequence homogenization has replaced HRS60 family repeats at sub-telomeric regions, but that this process may not occur, or occurs more slowly, when the repeats are found at intercalary locations. Sequence homogenization acts more rapidly (at least two orders of magnitude) on 35S rDNA than 5S rDNA and sub-telomeric satellite sequences. This rapid rate of divergence is analogous to that found in polyploid species, and is therefore, in plants, not only associated with polyploidy.

Chromosomes, Plant↗

PubMed2004

Recombination and loss of complementation: a more than two-fold cost for parthenogenesis.

Certain types of asexual reproduction lead to loss of complementation, that is unmasking of recessive deleterious alleles. A theoretical measure of this loss is calculated for apomixis, automixis and endomitosis in the cases of diploidy and polyploidy. The effect of the consequent unmasking of deleterious recessive mutations on fitness is also calculated. Results show that, depending on the number of lethal equivalents and on the frequency of recombination, the cost produced by loss of complementation after few generations of asexual reproduction may be greater than the two-fold cost of meiosis. Maintaining complementation may, therefore, provide a general short-term advantage for sexual reproduction. Apomixis can replace sexual reproduction under a wide range of parameters only if it is associated with triploidy or tetraploidy, which is consistent with our knowledge of the distribution of apomixis.

Alleles↗

PubMed1977

Separation of isolated cell nuclei of tissues of the meal moth, Ephestia kuehniella Z. by metrizamide density gradient centrifugation.

The behaviour of isolated cell nuclei of different tissues in the mediterranean meal moth has been studied in metrizamide density gradients to find whether differences exist in the bouyant density between nuclei derived from different specialized tissues. The different nuclei studied have buoyant densities ranging form 1.228-1.295 g/cm3 in metrizamide density gradients and clear differences exist between different populations of nuclei. The different buoyant densities make it possible to separate isolated nuclei from a heterogeneous population of nuclei according to their characteristic densities. This has been tested by the separation of silk gland nuclei from follicle cell nuclei by the density centrifugation method. The degree of polyploidy of the nuclei is not correlated to a decrease or increase of the buoyant density, which suggests that different amounts of nuclear proteins, ribonucleoproteins or RNA are responsible for the differences determined. These tissue-specific differences of the nuclear densities might be correlated to different transcriptional activities. In addition to this, the isopycnic sedimentation technique in metrizamide density gradient provides a method to purify nuclei very carefully without any visible alteration of their morphology and integrity.

Animals↗

PubMedDate not supplied

Low-grade myxofibrosarcoma: progression in recurrence.

A case of low-grade myxofibrosarcoma with histologic progression in recurrence occurring in a 51-year-old male is described. The patient had a well-circumscribed encapsulated myxoid mass, which measured 2.5 cm at its greatest diameter, in the subcutis of the left forearm. Microscopically, the tumor was characterized by a proliferation of sparsely distributed spindle or stellate cells, curvilinear small vessels and myxoid stroma. It demonstrated mild pleomorphism without mitotic figures. The patient had the first recurrence at 3 years, which was histologically identical to the primary tumor. The patient had a second recurrence at 11 years, which was predominantly composed of sheets of anaplastic, rounded or oval cells with focal osteoid formation. Immunohistochemically, the tumor cells in the primary and the first recurrent lesions were focally positive for vimentin. In the second recurrence, the tumor cells contained vimentin, alpha-smooth muscle actin and muscle specific actin (HHF35). The primary lesion had a diploid DNA content with low S-phase fractions. The second recurrence showed a polyploidy. The patient was well with no evidence of disease 18 months after the second recurrence. These findings suggest that this neoplasm showed histological progression with an increasing risk of metastasis. Low-grade myxofibrosarcoma, which commonly is misinterpreted as benign, has a tendency for histological and biological progression in local recurrences, underlining the importance of accurate diagnosis and wide surgical excision of the primary lesion.

Actins↗