Liquid-based cytology and cell block immunocytochemistry in veterinary medicine: comparison with standard cytology for the evaluation of canine lymphoid samples

Multiple myeloma in dogs: Use of the cell block technique as a new diagnostic tool

BACKGROUND

The diagnosis of multiple myeloma (MM) in dogs may be challenging and complex. The cell blocks are a diagnostic technique that allows the characterization of neoplastic cells and, therefore, might help in the diagnosis of atypical MM.

OBJECTIVE

The objective of the present work is to describe three clinical cases in which the cell blocks and immunohistochemistry contributed to the definitive diagnosis of canine MM.

METHODS

Three dogs, one female and two males, with different clinical signs, were presented for consultation with anemia, hyperproteinemia with monoclonal gammopathy, and the presence of plasmacytosis in the bone marrow. Cytologic analysis of the spleen was performed in two dogs and was suggestive of the presence of lymphocytes or plasma cells of a neoplastic nature in one of the cases and plasma cell hyperplasia associated with extramedullary hematopoiesis in the other. Given the hypotheses of lymphoid neoplasms with a plasma cell phenotype, cell blocks from aspiration punctures were performed for immunohistochemical analysis with anti-CD3, CD20, CD79αcy, PAX5, and MUM1 antibodies.

RESULTS

The results revealed positive staining for MUM1 in 80% of the cells in the spleen cell block and for CD20 and MUM1 in 70% of the cells in the bone marrow cell blocks, with negative staining for the other antibodies. The immunophenotyping results allowed the diagnosis of MM in the three cases and excluded other lymphoid neoplasms.

CONCLUSIONS

This work reinforces the importance of using cell blocks in the diagnosis of neoplasms by demonstrating their potential to aid the diagnosis of MM.

Detection of Lymphoid Markers (CD3 and PAX5) for Immunophenotyping in Dogs and Cats: Comparison of Stained Cytology Slides and Matched Cell Blocks

Immunolabeling on Romanowsky-stained cytology (RSC) slides can be used, although there is limited evidence of its suitability for phenotyping canine and feline lymphomas. A comparison with matched cell blocks (CB) is missing. Immunolabeling on RSC and CB was compared for lymphoid markers (CD3 and PAX5) in 53 lymphomas and 4 chylous effusions from dogs and cats. The influence of pre-analytical variables (species, time of archive, type of specimens and coverslipping) and the interobserver agreement among the 2 observers was assessed. Fewer CD3+ lymphocytes were identified in RSC, while the PAX5 positivity by RSC and CB had a substantial agreement. Immunodetection of CD3 and the diagnosis of a T-cell population on RSC was more difficult. Lower intensity and higher background were noted in RSC. Immunophenotyping was inconclusive in 54% RSC and 19% CB. The interobserver reproducibility of immunophenotyping on CB was substantial, being higher than in RSC. The immunolabeling performance on the RSC of effusion and feline samples was unsatisfactory. The detection of lymphoid markers, especially membranous antigens in retrospective RSC, is affected by the pre-analytical variables: species, time of the archive, and type of specimens. CB are a more consistent type of sample for immunophenotyping purposes.

Co-Expression of T- and B-Cell Markers in a Canine Intestinal Lymphoma: A Case Report

An 8-year-old female neutered Labrador retriever was presented for a second opinion consultation due to vomiting and lethargy, having failed to respond to symptomatic therapy. Blood analysis revealed hyperbilirubinemia and hypoalbuminemia, associated with hypocobalaminemia. An abdominal ultrasound identified diffused bowel thickening and hypoechoic hepatomegaly. An ultrasound-guided liver fine-needle aspiration was performed for cytology and also for cell block immunocytochemistry. Gastric and duodenal biopsies were collected by gastroduodenoscopy. Liver cytology showed numerous lymphocytes, suggesting lymphoma at the hepatic infiltration stage, and immunocytochemistry in the cell block of the hepatic aspirate indicated co-expression of CD3 and CD20 in the lymphoid cells present. The histopathology of gastric and duodenal biopsies supported the hypothesis of gastrointestinal lymphoma due to heavy lymphoid infiltration of the gastric epithelium and intestinal mucosa, including the villi. Concurrent immunohistochemistry was performed using CD3, CD20, PAX5, and CD79αcy antibodies. Immunomarking was positive for CD3 and CD20, which overlapped populations of lymphoid cells, and was negative for all other antibodies. In the clonality test, lymphocyte co-expression of CD3 and CD20 was confirmed by monoclonal rearrangement of T-cell gamma receptors. The final diagnosis was type 2 enteropathy-associated T-cell lymphoma with hepatic infiltration. Co-expression was examined in conjunction with the PARR result in the presence of T-cell monoclonal rearrangement.

Evaluation of DNA/RNA quality from cell block of malignant mesothelioma and lung adenocarcinoma

Malignant mesothelioma (MM) is a rare and highly lethal tumor that arises from mesothelial tissue on the surface of the chest and abdominal cavity. Cytological examination of body fluids, including pleural fluid and ascites, is essential for the differentiation of malignant mesothelioma from other carcinomas, such as lung and gastrointestinal carcinomas and metastatic tumors. To evaluate the effectiveness of cell block preparation procedures, which are used for immunocytochemical staining and genetic panel analysis of tumor-specific gene mutations, we used various fixatives. We also evaluated the effects of immunostaining, and the quality of nucleic acids for genetic analysis.

METHODS

Cell blocks were prepared using the malignant mesothelioma cell lines MESO4 and H226 and non-small cell lung carcinoma cell line HCC78. The cells were fixed using 10% neutral buffered formalin and four different fixatives for liquid cytology. Fixed cells were formed into cell clusters using sodium alginate or centrifugation, and paraffin-embedded cell blocks were prepared.

RESULTS

Cell blocks were morphologically evaluated by hematoxylin and eosin and immunocytological staining, and the nucleic acid quality was evaluated by DNA/RNA extraction, qPCR, and next-generation sequence analysis. D2-40 and WT1 staining differed depending on the fixation solution and the cell cluster formation method; however, the degree of nucleic acid degradation was not impaired by any method.

CONCLUSION

Although the morphological evaluation of cytology specimens is affected by the method of cell block preparation, it is still useful for nucleic acid extraction and gene panel analysis, as long as there are sufficient amounts of tumor cells.

Feline mesothelioma: case report and review of cytologic, immunocytochemical, histopathologic, and immunohistochemical findings

Mesotheliomas are uncommon neoplasms that arise from mesothelial cells in either the abdominal or thoracic cavities and are rarely diagnosed in cats. A 10-y-old spayed female domestic shorthair cat was presented to the Louisiana State University oncology service for evaluation of a large amount of abdominal effusion. Abdominal ultrasound identified a large mesenteric mass with numerous ill-defined nodules. An abdominocentesis was performed with cytologic and immunocytochemical findings consistent with a neoplastic effusion, with large clusters of epithelioid cells that exhibited strong cytoplasmic expression of pancytokeratin, vimentin, and Wilms tumor 1 antigens. Further testing was declined, and meloxicam was prescribed until the cat died 23 d after initial presentation. Upon postmortem examination, the omentum was contracted into a firm mass adhered to multiple organs and accompanied by numerous small white nodules throughout the abdominal cavity. On histopathology and immunohistochemistry, neoplastic cells were found throughout the abdominal cavity; 60-95% exhibited moderate-to-strong cytoplasmic immunoreactivity for cytokeratin, vimentin, and Wilms tumor 1 protein. The final diagnosis was an epithelioid mesothelioma. Our case illustrates the utility of cytology, immunocytochemistry, and its relation to histology and immunohistochemistry. We also reviewed the reported cases of feline mesothelioma.

Specimen-specific cell-blocking approaches

The science of CellBlockistry highlights requirement for proper approach to process different types of cytopathology specimens with critical considerations during preparation of cell-blocks. Common cytopathology specimens which may be subjected for cell-blocking include FNA aspirates in addition to anterior fat pad aspirate, bone marrow aspirate, effusion fluids, and other fluids such as various washings and urine. In addition veterinary sciences and research fields including animal experiments and tissue/cell cultures may also be cell-blocked for improved diagnostic yield and research outcome.

Cell blocks in veterinary medicine: A comparison of two methods (cell tube and agar) in 52 effusions from dogs and cats

BACKGROUND

Cell blocks are alternative preparations of fluid cytological specimens. They can be used for immunochemical studies as complementary tools or when other techniques (eg, immunocytochemistry, flow cytometry) are not available.

OBJECTIVES

We aimed to provide comparative morphologic, immunohistochemical, and technical features of agar-based cell blocks (ACBs) and cell tube blocks (CTBs) from cavitary effusions.

METHODS

Agar-based cell blocks and CTBs were obtained from canine and feline effusions with neoplastic/atypical cells or with packed cell volumes ≥3%. Cellularity, RBC separation, and cellular features were evaluated on digitalized H&E slides with evaluators blinded to the method. The immunohistochemical intensity and nonspecific background were assessed on pan-cytokeratin and vimentin-stained slides. Overall yield was calculated, and morphologic and immunohistochemical features were compared among paired samples. Technical and cellular features were also described.

RESULTS

Agar-based cell blocks and CTBs yielded evaluable sections in 100% (52/52) and 98% (51/52) of the cases, respectively. Cellularity and RBC separation scores were significantly higher in CTBs. Similar staining intensities were observed, and background staining was more frequently seen in pan-cytokeratin-stained ACBs. Only basic materials and equipment were required for both methods. Agar-based cell block preparations were more operator dependent and difficult to standardize, whereas CTBs were easier to prepare, but laboratory processing was more demanding.

CONCLUSIONS

Both methods can be used to produce good sections for immunohistochemistry staining with no significant differences. Cell tube blocks are beneficial for RBC-rich samples, and little additional training is required to prepare the blocks. Both types of cell blocks are reliable, cost-effective methods that could be introduced in diagnostic laboratories to further characterize canine and feline effusions.

Evaluation of Cytopathological Techniques for the Diagnosis of Canine Visceral Leishmaniosis with Lymph Node Samples

The identification of the parasite in cytological smears of lymph node aspirates is a widely applied technique for the direct diagnosis of Leishmania spp. infection, especially in endemic areas. Although very specific, this method has limited sensitivity, and improving the technique would be highly desirable. This study aimed to evaluate the efficacy of conventional smear cytology (SC), liquid-based cytology (LBC), cell block (CB) stained with haematoxylin and eosin (HE) and immunocytochemistry (ICC), and formalin-fixed paraffin wax-embedded tissue immunohistochemistry (FFPE-IHC) compared with serology and polymerase chain reaction for the diagnosis of canine visceral leishmaniosis (CVL) in lymphoid tissue. The use of a preservative medium and centrifugation for cytological samples reduced the number of unsatisfactory artefacts/background. Moreover, LBC allowed excellent cellular preservation and the application of ancillary techniques, such as CB and ICC. SC was the most accurate morphological diagnostic method (45.0%). CB-ICC alone or associated with SC demonstrated significantly higher sensitivity (70.0% and 72.0%, respectively) when compared with SC alone (34.00%). CB-ICC was found to be more effective in the detection of infected animals with mild clinical signs, similar to FFPE-IHC. The specificity and positive predictive value were similar between all methods. Finally, the detection limit for CB-ICC and SC + CB-ICC was identical (18.46 amastigotes/mm²). Our study suggests that CB-ICC is a promising tool for improvement of the cytopathological diagnosis of CVL and may be applied in routine epidemiological screening.

Novel Noninvasive Diagnostics

Molecular diagnostics have revolutionized human oncology to allow early detection, targeted therapy, monitoring throughout treatment, and evidence of recurrence. By identifying genetic signatures associated with cancers, liquid biopsy techniques have been developed to diagnose and monitor cancer in noninvasive or minimally invasive ways. These techniques offer new opportunities for improving cancer screening, diagnosis, and monitoring the impact of therapy on the patients over time. Liquid biopsy also drives drug development programs. Similar diagnostics hold promise for comparable results in the veterinary field. Several noninvasive/minimally invasive techniques have been described in veterinary medicine that could be referred to as liquid biopsy.

Cytology and the cell block method in diagnostic characterization of canine lymphadenopathy and in the immunophenotyping of nodal lymphoma

Minimally invasive techniques used to evaluate canine peripheral lymphadenopathy (PLN), including fine needle aspiration biopsy with cytological evaluation (FNAB-C) and flow cytometry (FC), have benefits and limitations. The cell block (CB) method is an alternate processing technique in which fine needle aspirate biopsy samples are concentrated, fixed, and embedded in paraffin for routine histological processing/staining. Utilizing three observers, we determined the diagnostic value of the CB in evaluating canine PLN across six categories (non-diagnostic, reactive, inflammatory/infectious, probable lymphoma and lymphoma, metastatic neoplasia) and correlated findings to immunophenotypic and clonal antigen receptor rearrangement results in canine nodal lymphoma. Eighty-five paired FNAB-C and CB samples were evaluated from canine patients presenting to the University of Minnesota Veterinary Oncology or Internal Medicine services. Diagnostic quality samples were obtained in 55/85 (65%) CB and 81/85 (95%) FNAB-C samples, respectively, and nodal pathology impacted CB diagnostic yield. Overall percent agreement between diagnostic-quality FNAB-C and CB samples was 86%, but increased to 95% if the categories of lymphoma and probable lymphoma were combined. There was 100% agreement for both the diagnoses of metastatic neoplasia and reactive lymph nodes and 92% agreement for the diagnosis of lymphoma/probable lymphoma. Using immunohistochemistry (IHC), CB samples correctly immunophenotyped 22/23 (96%) cases of B-cell lymphoma, but only 1/6 (17%) cases of T-cell lymphoma. IHC was not completed on nine cases of lymphoproliferative disease because of insufficient cellularity. When the CB method (CBM) yielded diagnostic quality samples there was good to excellent agreement with FNAB-C samples and CB samples were suitable for some IHC tests.

Global DNA methylation of peripheral blood leukocytes from dogs bearing multicentric non-Hodgkin lymphomas and healthy dogs: A comparative study

Non-Hodgkin lymphomas are among the most common types of tumors in dogs, and they are currently accepted as comparative models of the disease in humans. Aberrant patterns of DNA methylation seem to play a key role in the development of hematopoietic neoplasms in humans, constitute a special mechanism of transcriptional control, and may be influenced by genetic and environmental factors. Blood leukocyte DNA global methylation has been poorly investigated in dogs. The aim of this study is to examine whether peripheral blood global DNA methylation is associated with canine multicentric lymphomas. Peripheral venous blood samples from ten healthy dogs and nine dogs bearing multicentric lymphomas were collected, and the buffy coat was separated. Global DNA methylation was analyzed by High Performance Liquid Chromatography (HPLC) and immunocytochemistry (ICC). In both analyses, leukocytes from dogs with lymphoma presented lower global DNA methylation than in healthy dogs (HPLC: p = 0.027/ 5MeCyt immunoreactivity scores: p = 0.015). Moderate correlation was observed between the results obtained by HPLC and ICC (correlation coefficient = 0.50). For the identification of differently methylated genes between both groups, the Infinium Human Methylation (HM) EPIC BeadChip (850K) was used. Of the 853,307 CpGs investigated in the microarray, there were 34,574 probes hybridized in the canine samples. From this total, significant difference was observed in the methylation level of 8433 regions, and through the homologous and orthologous similarities 525 differently methylated genes were identified between the two groups. This study is pioneer in suggesting that dogs bearing non-Hodgkin lymphoma presented DNA global hypomethylation of circulating leukocytes compared with healthy dogs. Although canine samples were used in an assay developed specifically for human DNA, it was possible to identify differently methylated genes and our results reiterate the importance of the use of peripheral blood leukocytes in cancer research and possible new biomarkers targets.

The cell tube block technique and an immunohistochemistry panel including Wilms tumor 1 to assist in diagnosing cavitary effusions in dogs and cats

BACKGROUND

Cell blocks and immunohistochemistry (IHC) are increasingly recognized as being complementary tools for cytologic diagnostics, especially for neoplastic diseases.

OBJECTIVES

The study aimed to evaluate the utility of cell tube block (CTB) IHC for refining the diagnosis of effusions in dogs and cats.

METHODS

Cavitary effusions (n = 25) from dogs and cats classified by cytology as reactive, neoplastic, borderline (suspicious of neoplasia), and chylous were studied. CTB sections were stained with H&E, and immunostained with PAX-5, CD3, pancytokeratin (CK), vimentin, and Wilms tumor 1 protein (WT1) antibodies, according to the cytologic diagnoses. A histologic case series of confirmed normal, reactive, and neoplastic mesothelium and several different carcinomas were included to test the utility of WT1 as a marker of mesothelial cells.

RESULTS

CTBs had a layered appearance with reduced background staining. CD3 and PAX5 immunolabeling allowed immunophenotype assessment in all of the lymphoma cases. In carcinomatous effusions, neoplastic cells were CK-positive, WT1-negative, and vimentin-negative (except for two cases). Wilms tumor 1 protein was positive in the nuclei of normal, reactive, and neoplastic mesothelial cells, and ovarian carcinomatous cells. Other carcinomas and lymphomas were negative.

CONCLUSIONS

CTBs are valuable tools to assist in making a diagnosis of cavitary effusions in dogs and cats, and WT1 is a promising marker to differentiate mesothelial from carcinomatous cells.

Feline Sporothrix spp. detection using cell blocks from brushings and fine-needle aspirates: Performance and comparisons with culture and histopathology

BACKGROUND

Sporotrichosis is an emerging zoonotic mycosis that presents as a cutaneous lymphatic or disseminated disease, caused by fungi from the Sporothrix schenkii (S schenkii) clinical clade. Its importance is growing, primarily due to an outbreak that occurred in Brazil, affecting mainly cats and people.

OBJECTIVES

In Brazil, an S schenkii diagnosis is often made using cultures, which allows genus identification and sufficient growth to perform molecular biology testing. Despite its advantages, fungal cultures are slow to develop and can delay public health measures, highlighting the importance of developing additional diagnostics techniques.

METHODS

Cell block cytology (CBLC) is an older method that regained importance after liquid-based cytology (LBC) was introduced, and it has been previously and successfully applied to veterinary diagnostics. We aimed to standardize and compare CBLC from cervical brush exfoliation of open wounds and fine-needle aspirates with culture and immunohistochemistry of skin biopsies for sporotrichosis in cats, as a novel method.

RESULTS

For this purpose, we selected 40 cats with skin lesions suspected of having sporotrichosis in Guarulhos city, São Paulo state, Brazil. We achieved 97.5% and 95% positivity using CBLC and culture, respectively, and 100% of feline skin biopsies were positive for Sporothrix spp on histopathology/immunohistochemistry.

CONCLUSIONS

Cell block cytology is an efficient and rapid tool to diagnose sporotrichosis in cats, particularly during epidemics.