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At least 163 records · Page 9Linked to original sources
PubMed2006

Diagnosis of clear cell sarcoma by real-time reverse transcriptase-polymerase chain reaction analysis of paraffin embedded tissues: clinicopathologic and molecular analysis of 44 patients from the French sarcoma group.

BACKGROUND: Clear cell sarcoma (CCS) is a rare tumor with a very poor prognosis that occurs predominantly in the distal extremities of young adults. Most patients bear the t(12;22) reciprocal translocation, which involves the EWS and ATF1 genes. The diagnosis of CCS usually is easy but may be challenging in unusual sites, and the detection of EWS-ATF1 fusion transcripts is helpful to rule out a metastatic melanoma. METHODS: Forty-four patients with CCS and 14 conventional melanomas were examined for the presence of EWS-ATF1 transcripts by using real-time polymerase chain reaction (PCR) analysis on paraffin embedded tissues, including frozen samples for 9 CCS samples and 9 melanoma samples. Prior to molecular analysis, the diagnosis of CCS was considered certain in 35 patients and as probable in 9 patients on the basis of location, histologic features, and immunohistochemical profile. Treatment modalities and follow-up were available for 41 patients with CCS. RESULTS: EWS-ATF1 fusion transcripts were detected in 38 paraffin embedded CCS tissues (86% of all samples; 93% of interpretable samples), 3 samples (7%) were negative, and 3 samples (7%) were considered uninterpretable. Fusion transcripts were detected in 7 of 9 samples for which the diagnosis of CCS was considered probable. EWS-ATF1 transcripts were not detected in the 14 samples of melanoma. Results from frozen tissues were concordant with those from all corresponding paraffin embedded samples. Twenty-eight of 41 patients (68%) experienced lymph node and/or distant metastasis, and the 5 year-survival rate was 44%. Mitotic index and histologic grade were predictive of survival and distant metastasis. CONCLUSIONS: The results of this study showed that the molecular detection of EWS-ATF1 fusion transcript by real-time PCR on paraffin embedded tissues is a sensitive and specific method for the diagnosis of CCS. It is an efficient tool for the diagnosis of unusual tumors, especially with regard to its distinction from melanoma. The current results also confirmed the poor prognosis for patients with this tumor type. Mitotic index and grade were predictive factors for survival and distant metastasis.

Adolescent↗
PubMed2007

Dose-response feeding study of short chain chlorinated paraffins (SCCPs) in laying hens: effects on laying performance and tissue distribution, accumulation and elimination kinetics.

Technical short chain chlorinated paraffins (C10-C13 with 60% chlorine) were fed to 93 laying hens from 24 to 32 weeks of age in increasing concentrations of up to 100 mg/kg feed. No significant influence on health, relative organ weights or performance (laying intensity, egg weight, feed consumption) was noted. The chlorinated paraffin content of the tissues was linearly related to the concentration of short chain paraffins of the feed. The highest concentrations were found in abdominal fat, egg yolk and fatty tissues. Breast muscle, egg albumen and bile fluid contained minimal or no residues. Less than 1% of the chlorinated paraffins ingested were incorporated into the body (without head, feet, gut and feathers), whereas about 1.5% were eliminated with the egg yolk and 30% were excreted with urine and faeces. A six-week kinetic depuration study revealed a biphasic elimination with half-lifes of 4-40 min (liver, kidneys, legs, fat, blood) for the initial rapid phase, and 15-30 days (blood, fat, liver, yolk, kidneys, legs) for the terminal slow phase.

Animals↗
PubMed1986

The demonstration of B-cell, T-cell and myeloid antigens in paraffin sections.

The monoclonal antibodies MB1 and MT1, which detect B cells and T cells respectively, have been applied to human lymphoid tissues. The distribution of staining within paraffin sections was compared with that observed using frozen sections and was found to be identical. The antibodies were then applied to paraffin sections of 19 B-cell lymphomas and 10 T-cell lesions in which full immunophenotyping had been performed. The B lymphomas all consisted of a large majority of MB1 positive cells with a variable infiltrate of small MT1 positive lymphocytes. The T cell lesions consisted of MT1 positive cells with few MB1 positive cells except in residual B cell areas of lymph nodes. In paraffin sections from cases of Hodgkin's disease anti-Leu M1 identified Reed-Sternberg cells and their variants and MB1 and MT1 showed a similar distribution of B cells and T cells to that demonstrated in previous studies using frozen sections. The results show that MB1 and MT1 are useful markers for B and T cells in routinely fixed paraffin embedded tissue. In conjunction with anti-Leu M1 they provide a valuable panel of antisera for the examination of lymph nodes and other biopsies when frozen tissue is not available.

Antibodies, Monoclonal↗
PubMed1992

Monoclonal antibodies against recombinant parts of the Ki-67 antigen (MIB 1 and MIB 3) detect proliferating cells in microwave-processed formalin-fixed paraffin sections.

The monoclonal antibody Ki-67 reacts with a human nuclear cell proliferation-associated antigen that is expressed in all active parts of the cell cycle. Recently we have raised monoclonal antibodies, MIB 1-3, against recombinant parts of the Ki-67 antigen. These antibodies are true Ki-67 equivalents, as demonstrated by immunostaining of fresh specimens, biochemistry, and molecular biological techniques. Formalin-fixed, paraffin-embedded sections routinely processed for immunohistochemistry failed to stain for Ki-67 and MIB 2. Antibodies MIB 1 and MIB 3 labelled mitotic figures, while non-mitotic proliferating cells were negative under these conditions. However, when dewaxed microwave oven-processed paraffin sections of formalin-fixed tissues were used, MIB 1 and MIB 3 gave strong nuclear staining of those cells presumed to proliferate under a variety of normal and neoplastic conditions. Moreover, routine decalcification or depigmentation techniques did not alter the immunoreactivity of MIB 1 and MIB 3 with microwave-processed paraffin sections. This method is highly reproducible, easy to perform at low cost, and no additional technical skill is needed because after microwave treatment just routine immunohistochemical methods are used. Since we have successfully applied this new method to sections obtained from paraffin blocks stored for a long time (in one case more than 60 years), the assessment of cell kinetics through the detection of Ki-67 antigen is now possible on archival material collected in histopathology departments all over the world.

Antibodies, Monoclonal↗
PubMed1995

A cautionary note regarding the application of Ki-67 antibodies to paraffin-embedded breast cancers.

Immunocytochemical studies examining the Ki-67 proliferation marker in paraffin-embedded material have recently been made possible by the availability of several antibodies, notably MIB-1, which are readily applicable to microwaved sections. Using breast cancer material, the present study examines correlations shown by these new paraffin assays and also by PCNA (proliferating cell nuclear antigen), an existing marker of proliferation, with the established Ki-67 cryosection assay. Paraffin sections were microwaved prior to incubation with Ki-67 or MIB-1 antibodies. Signal detection was carried out with a biotinylated secondary antibody, peroxidase-conjugated streptavidin, and DAB/H2O2 chromogen. The results suggest that caution is required when studying proliferation in paraffin-embedded breast cancers by immunostaining using Ki-67 antibodies. Nuclear staining in wax sections (Ki-Par, MIB-1, PCNA) greatly exceeded that in cryosections (Ki-Froz) and thus correlations were notably absent between Ki-Par or PCNA immunostaining and the routine Ki-Froz assay. Immunostaining with MIB-1 or PCNA may, however, be useful to assess proliferation if cut-offs are applied to eliminate weak immunostaining associated with wax sections. Thus, an approximately linear relationship was seen between MIB-1/Ki-Froz, which was improved if only moderately or moderately/strongly MIB-1-positive cells were scored. Similarly, a significant correlation was also revealed between PCNA/Ki-Froz if such a cut-off was applied.

Antibodies, Monoclonal↗
PubMed2006

Transfer and multiplex immunoblotting of a paraffin embedded tissue.

As we transition from genomics to the challenges of the functional proteome, new tools to explore the expression of proteins within tissue are essential. We have developed a method of transferring proteins from a formalin fixed, paraffin embedded tissues section to a stack of membranes which is then probed with antibodies for detection of individual epitopes. This method converts a traditional tissue section into a multiplex platform for expression profiling. A single tissue section can be transferred to up to ten membranes, each of which is probed with different antibodies, and detected with fluorescent secondary antibodies, and quantified by a microarray scanner. Total protein can be determined on each membrane, hence each antibody has its own normalization. This method works with phospho-specific antibodies as well as antibodies that do not readily work well with paraffin embedded tissue. This novel technique enables archival paraffin embedded tissue to be molecularly profiled in a rapid and quantifiable manner, and reduces the tissue microarray to a form of protein array. This method is a new tool for exploration of the vast archive of formalin fixed, paraffin embedded tissue, as well as a tool for translational medicine.

Antibodies, Phospho-Specific↗
PubMed1996

Oligosaccharide release from frozen and paraffin-wax-embedded archival tissues.

Altered glycosylation is a feature of many solid tissue diseases such as ulcerative colitis, Crohn's disease, cancer, and connective tissue disorders. Conventionally, oligosaccharide changes have been studied by immunohistochemical techniques. We have adapted existing techniques, developed for purified protein preparations, to allow the release of intact oligosaccharides from archival tissues, so that the oligosaccharides may be structurally characterized. In our study, sections cut from paraffin-wax blocks were dewaxed and oligosaccharides were released using hydrazine and labeled with 2-aminobenzamide. Sialylated oligosaccharides were compared by passing through a GlycoSep C divinylbenzene anion exchange resin column and neutral oligosaccharides were compared by passing through a BioGel P4 column. The oligosaccharide profiles obtained from the same fresh frozen versus archival paraffin-wax-embedded, normal liver, and tumor tissues showed remarkable similarity in terms of their sialylated and neutral structures. Matrix-assisted laser desorption ionization mass spectrometry has shown that the oligosaccharides are not affected by fixation in formalin and storage in paraffin wax. The results indicate that while the proteins themselves may be denatured, oligosaccharides are not adversely affected by fixation in formalin and storage in paraffin wax. By applying these methods, oligosaccharides from archival tissues, where the natural history of the disease has been followed, may now be liberated and structurally characterized.

Animals↗
PubMed1992

Cryofixed, freeze-dried and paraffin-embedded skin enables successful immunohistochemical staining of skin basement membrane antigens.

Conventional chemical fixation and paraffin-embedding procedures give good preservation of morphology, although the antigenicity of many proteins in the tissue sample is destroyed. On the other hand, fresh frozen sections can preserve the antigenicity, but provide poor morphological preservation. To overcome this dilemma, cryofixation and freeze drying were used on human skin tissue, applying methodology which has only been used to study lymphoid tissue. First, fresh human skin was cryofixed in liquid isopentane (-160 degrees C) cooled by liquid nitrogen. The skin was then freeze-dried at -40 degrees C and 10(-2) atmospheric pressure for 72 h, followed by embedding in paraffin. Sections 4 microns thick taken from this cryofixed, freeze-dried, and paraffin-embedded skin were stained with hematoxylin-eosin or used for immunolabeling with antibodies against basement membrane antigen, including type IV and type VII collagen, bullous pemphigoid antigen, epidermolysis bullosa acquisita antigen, and GB3 antigen. The morphological preservation of these sections was as good as that of routine formalin-fixed and paraffin-embedded skin sections. The basement membrane was clearly immunostained with all antibodies used, and the intensity of the reaction was as strong as that seen in frozen sections. Evaluation of antigen distribution in conjunction with the detailed skin structure was therefore possible in the same sections.

Antibodies, Monoclonal↗
PubMed2003

Fluorescence in situ hybridization detection of chromosome IGH/BCL2 translocations from paraffin-embedded tissue: evaluation in follicular lymphoma.

Follicular lymphoma is categorized as low-grade lymphoma because of the long median survival, but the disease is difficult to cure because of frequent recurrence. The t(14;18)(q32;q21) associated with follicular lymphoma juxtaposes a portion of BCL-2 (18q21) and IGH(14q32); the result is bcl-2 overexpression. In this study, a highly sensitive 2-color fluorescence in situ hybridization (FISH) method was used to detect t(14;18)(q32;q21) in the nuclei of paraffin-embedded tissue sections. Fourteen specimens, including 11 samples from follicular lymphoma and 3 samples from diffuse large cell lymphoma, for which results of karyotype study and paraffin-embedded tissues were available were selected for FISH study. The FISH results were compared with results of karyotype study of the lymph nodes involved in lymphoma. Among our 11 patients with the diagnosis of follicular lymphoma in whom karyotype study was performed, 8 had t(14;18)(q32;q21) in karyotype analysis, and 7 of these patients had a positive pattern in FISH analysis. In 1 case, FISH analysis was difficult because of weak signals. All 3 patients with diffuse large cell lymphoma and t(14;18)(q32;q21) in karyotype analysis had a positive pattern in FISH analysis. In 3 cases of follicular lymphoma without t(14;18)(q32;q21) in karyotype analysis, FISH did not show a positive pattern. Therefore the FISH assay in tissue was found to be very sensitive in detection of IGH/BCL2 translocation and was helpful in diagnosis of follicular lymphoma or in clarification of the cell origin of lymphoma when karyotype analysis was not available. Performing FISH on paraffin sections also is useful because we can identify cells with genetic abnormalities in the tumor and make a retrospective cytogenetic diagnosis even with old paraffin-embedded specimens.

Adult↗
PubMed2003

Pitfalls in assessment of progesterone production by granulosa cells cultured in contact with silicone rubber or paraffin oil.

BACKGROUND: The influence of silicone templates, used for compartmentalization of culture dishes, on progesterone accumulation in granulosa cell cultures is studied and compared with the effect of paraffin oil, which is frequently used to cover oocyte/embryo cultures. METHODS: Human granulosa-lutein cells were cultured in culture dishes compartmentalized by silicone templates, or in polystyrene plates under paraffin oil. Progesterone concentrations in the culture supernatant were compared with controls cultured in polystyrene plates. RESULTS: The progesterone concentration in culture supernatant was grossly reduced in silicone template cultures (2+/-0.7% of control). No inhibitory activity was identified in medium conditioned by preincubation with silicone rubber, but progesterone was absorbed from spiked medium incubated in silicone templates (recovery <2%). Progesterone concentration in culture supernatant was also reduced by a paraffin oil overlay (38+/-3% of control). From steroid spiked microdrops under oil, <2% of progesterone and 85+/-4% of estradiol was recovered. CONCLUSION: The steroidogenesis of cells cultured in silicone templates or under oil cannot be assessed correctly. It has to be considered that the concentration of lipophilic compounds may be grossly changed due to absorption by silicone rubber or paraffin oil.

Cell Culture Techniques↗
PubMed2003

Collection under paraffin is not necessary for stability of urine pH over 24 h.

Collection of urine under paraffin is routinely used in clinical practice for urine pH evaluation. To examine whether the accuracy of pH measurement is adversely influenced by the method of collection and storage, we divided each urine specimen and sent one aliquot to the laboratory under paraffin and another in a sealed 5-ml plastic syringe. In another experiment we evaluated the stability of urine pH measurement in a clinical setting. Urine collected under paraffin was tested immediately for pH; an aliquot from the same specimen was stored in a capped 5-ml syringe at 4 degrees C and tested after 24 h. We found no appreciable difference in measured pH between samples sent to the laboratory under paraffin or in a capped plastic syringe.

Circadian Rhythm↗
PubMedDate not supplied

Microdissection and gene rearrangement analysis of paraffin-embedded specimens of orbital malignant lymphoma.

PURPOSE: To determine whether a definite diagnosis of malignant lymphoma can be made from paraffin-embedded archived orbital specimens by gene rearrangement analysis using microdissection and polymerase chain reaction (PCR). METHODS: Specimens from four patients with histopathologically diagnosed orbital malignant lymphoma were examined. The malignant cells were microdissected off the paraffin-embedded specimens. DNA was extracted from the cells, and the immunoglobulin heavy chain ( IgH) gene was amplified by PCR. Gene rearrangements were detected by using primers for the third framework (FR3A), the second framework (FR2A), and the complementary determining region 3 (CDR3). Translocation of the B-cell lymphoma/leukemia-2 ( bcl-2) gene was also examined. RESULTS: Malignant cells were present on the slides of the paraffin-embedded specimens of three of four cases. The specimens from these three cases showed IgH rearrangements for FR3A, FR2A, and CDR3. A bcl-2-associated translocation was also detected in one case. CONCLUSIONS: Gene rearrangement analysis is applicable to paraffin-embedded archived orbital specimens to confirm a diagnosis of malignant lymphoma. The advantage of this method is that only a small specimen is needed because the detection sensitivity is high.

Complementarity Determining Regions↗
PubMed1975

Immunofluorescent detection of hepatitis B antigen in paraffin-embedded liver tissue.

Hepatitis B antigen (HBAg) has been demonstrated by the indirect immunofluorescent technique and by orcein staining in 20 liver biopsies fixed in Bouin's fixative and embedded in paraffin. The results were compared with those obtained previously by immunogluorescence on frozen sections of the same biopsies. Ten biopsies which were positive in frozen sections were also positive by immunofluorescence in parafin sections, whereas only six were positive by orcein staining. In orcein-stained sections, the cellular localization of HBAg was precisely in the same places as in the slides examined by immunogluorescence. The intessity of the fluorescence in paraffin sections was almost the same as in frozen sections. The localization of the antigen was histologically more precise in paraffin sections. Besides various advantages, indlucing aboidance of freezing aquipment and procedures, paraffin sections are more easy to handle and biopsies from distant hospitals can be processed. The advantages of the immunofluorescent test in comparison to orcein staining are its immunological specificity and higher sensitivity.

Biopsy↗
PubMed1992

Anti-CD34 immunoperoxidase staining in paraffin sections of acute leukemia: comparison with flow cytometric immunophenotyping.

Anti-CD34 is a monoclonal antibody that reacts with bone marrow progenitor cells and leukemic blasts, and is expressed on 30% to 50% of all acute leukemias. Detection of CD34 has previously been restricted to flow cytometric studies. To expand the utility of CD34, we immunostained 46 paraffin-embedded bone marrow specimens with acute leukemia; results were compared with flow cytometric studies. CD34 reactivity was also evaluated in nine chronic leukemia cases, 27 malignant lymphoma cases (Hodgkin's disease and non-Hodgkin's lymphoma), six normal bone marrow specimens, and three benign, hyperplastic lymph node specimens. All cases that were CD34 positive by flow cytometry (11 of 19 B-cell precursor acute lymphoblastic leukemia cases, one of six T-cell acute lymphoblastic leukemia cases, and seven of 21 acute myeloblastic leukemia cases) were also CD34 positive in paraffin sections. Both cell membrane and cytoplasmic staining was seen. The positivity percentage and fluorescence intensity by flow cytometry correlated with the estimated number of stained cells and the intensity of immunoperoxidase staining in 18 of 19 CD34-positive cases. The remaining bone marrow and lymph node cases studied were CD34 negative; prominent endothelial cell staining, however, was noted. This is the first report of anti-CD34 staining of acute leukemia in paraffin-embedded sections. In contrast to other monoclonal antibodies reactive in bone marrow paraffin sections with leukemia, anti-CD34 immunoperoxidase staining is limited to leukemic blasts and may provide useful diagnostic information when flow cytometric studies are not available.

Acute Disease↗
PubMed1994

Strategies for improving the immunohistochemical staining of various intranuclear prognostic markers in formalin-paraffin sections: androgen receptor, estrogen receptor, progesterone receptor, p53 protein, proliferating cell nuclear antigen, and Ki-67 antigen revealed by antigen retrieval techniques.

Different variations of the antigen retrieval technique using different retrieval solutions have been evaluated for their effectiveness in restoring the antigenicity of six intranuclear antigens, each of which is a potentially valuable prognostic indicator in formalin-fixed, paraffin-embedded tissue sections. The results of immunohistochemical staining for estrogen receptor, progesterone receptor, androgen receptor, p53 protein, proliferating cell nuclear antigen, and Ki-67 antigen were compared following the different antigen retrieval approaches. The strongest immunostaining signal with the clearest background was obtained by microwave heating of dewaxed paraffin sections for 10 minutes in 0.05 mol/L glycine HCl (pH 3.5) or in citrate buffer solution (pH 6). Urea solution, distilled water, and lead thiocyanate solution yielded improvements with some antigens, but less consistently and less impressively than glycine HCl buffer or citrate buffer. Following antigen retrieval nuclear staining was sharply defined and could be achieved consistently in a variety of tissues after formalin fixation for as long as 7 days. The duration of fixation, however, was an important variable; generally, the longer the fixation time the more vigorous the retrieval procedure required. This study demonstrates the ability to stain a variety of intranuclear antigens, which are not readily demonstrable otherwise, in formalin-paraffin sections with a high degree of consistency and reproducibility. The availability of methods that are effective in paraffin sections may facilitate studies of the possible value of these markers as prognostic indicators for predicting the response of major tumors to different forms of therapy. This study also provided insight into the basic principles of the antigen retrieval method, which may be helpful in attempts to develop a more uniformly standardized technique applicable to many different antigen systems.

Antigens, Neoplasm↗
PubMed1993

Detection of aneuploidy and possible deletion in paraffin-embedded rhabdomyosarcoma cells with FISH.

Conventional cytogenetic studies of solid tumors are limited by the difficulty of culturing tumor cells, while in situ hybridization using paraffin sections of interphase cells results in too many truncated cells. To solve these problems, fluorescent in situ hybridization (FISH) technique was used on free nuclei isolated from formalin-fixed paraffin-embedded embryonal rhabdomyosarcoma (RMS) tissue using our modification of Hedley's method for isolation of nuclei. Biotinylated DNA probes for the centromeric regions of chromosomes 6, 8, 11, 12, 17, and 18, painting probes for chromosomes 8 and 11, and a cosmid probe for the HER-2/neu oncogene, were used. The centromeric probes worked well, demonstrating two copies of chromosomes 6, 17, and 18, but three copies of chromosome 11 in 52.9% of nuclei. Four copies of chromosome 8 were observed in 57.1% of nuclei and five or more in 17.1%. Chromosome 12 demonstrated 21.8% trisomy and 62.2% tetrasomy. Painting probes for chromosome 11 also worked well and matched the results of the centromeric probes, with no suggestion of structural aberration. However, the results of the painting probe for chromosome 8 yielded fluorescent areas of different sizes, suggesting that some of the extra chromosomes 8 could be deleted. The cosmid probe for the HER-2/neu oncogene also worked well, and revealed two signals in each nucleus without evidence of amplification. This study illustrates the successful use of a new technique for studying chromosomal aberration in paraffin-embedded solid tumors. The importance of this technique is that it has not been previously possible to use painting probes or cosmid probes on paraffin tissue sections. Use of this procedure will broaden the type of retrospective studies that can be performed to include detection of deletions or translocations.

Aged↗
PubMed1993

Optimization of extraction and PCR amplification of RNA extracts from paraffin-embedded tissue in different fixatives.

A method was developed for fast and efficient isolation of RNA from paraffin-embedded tissue sections for subsequent PCR analysis. This method is based on the binding of RNA to acid-treated glass beads in the presence of a high molarity of guanidinium salt. It can be completed within an hour, and obviates the need for dewaxing and phenol/chloroform extractions. The effect of various fixatives and fixation times was tested and the amplification of actin mRNA fragments ranging in length from 82 to 507 bp was used to demonstrate the presence of RNA in the extracts. The method was compared to existing extraction techniques by studying the quality of the templates for reverse-transcriptase polymerase chain reaction amplification (RT-PCR), using virus-infected and mock-infected paraffin-embedded cell pellets as a model. PCR amplification of cellular and viral RNA was successful for RNA isolated by use of all extraction techniques, although the glass bead method was preferred for its simplicity and rapidity. Specimens fixed with formalin were found to be suitable for PCR, but the best results were obtained with acetone-fixed paraffin-embedded material. Dewaxing of tissue sections had no effect on the yield and quality of RNA extractions, and further purification of the extracts using gel filtration did not improve the results. After the protocols were optimized, rotavirus-infected cell pellets were used to demonstrate that extraction and amplification of dsRNA was possible. The information obtained from the studies with the model system was used for extraction of toroviral and rotaviral RNA from archival intestinal material. These data indicate that paraffin-embedded archival tissue can be used for RT-PCR analysis, adding an important technique to diagnostic pathology and retrospective studies.

Animals↗
PubMed1994

The duration of fixation influences the yield of HCV cDNA-PCR products from formalin-fixed, paraffin-embedded liver tissue.

The extent of hepatitis C virus (HCV) RNA loss during increasing periods of fixation of liver tissue in formalin was examined. For this purpose human liver tissue, known to be HCV RNA positive and stored at -70 degrees C until use, was cut into small slices (n = 9), which were fixed in phosphate-buffered formalin for increasing periods of time before embedding in paraffin. Nucleic acids were extracted from each slice of formalin-fixed, paraffin-embedded liver tissue and HCV RNA loss during fixation was semi-quantified by testing 10-fold dilutions of each extract in an HCV cDNA-PCR assay. The endpoint dilution for HCV RNA detection by cDNA-PCR in liver slices fixed in buffered formalin for 8-24 h was comparable to the endpoint dilutions found for 'fresh', non-fixed liver slices. After fixation for 2-3 days the endpoint dilution for HCV RNA detection was 10(2) to 10(3)-fold less. After 2-4 weeks of formalin-fixation, HCV RNA was detectable from undiluted nucleic acid extracts only. It is concluded that formalin-fixed, paraffin-embedded liver biopsies can be used for HCV RNA detection by cDNA-PCR, on condition that the liver tissue has been embedded in paraffin within 24 h of formalin-fixation.

Biopsy↗