Diagnostic Cytology in Veterinary Medicine: A Comparative and Evidence-Based Approach

Use of cytology for canine mammary masses and perceived diagnostic utility in four European countries

OBJECTIVES

To investigate the use of cytology of canine mammary masses and its perceived diagnostic utility in four European countries.

MATERIALS AND METHODS

The link to a web-based questionnaire was sent to veterinarians of Italy, UK, Greece and Spain. The questionnaire contained basic questions regarding the respondents' background, their general use of cytology as a diagnostic tool, the incidence of canine mammary tumours within their clinics and their use of cytology for canine mammary masses. Multiple binary and ordinal logistics models were used to evaluate associations between variables.

RESULTS

Four hundred and sixty-five veterinarians completed the survey (Italy: 114; UK: 66; Greece: 55; Spain: 230). Most veterinarians working in each country used cytology as a diagnostic tool, although only 43.0%, 54.6%, 43.6% and 36.5% used cytology for the investigation of CMMs in Italy, UK, Greece and Spain respectively. Supposing the cytology were able to correctly differentiate benign versus malignant canine mammary masses, the percentage of veterinarians using this test would increase in Italy, UK and Greece (Italy: 91.2%; UK: 93.9%; Greece: 96.4%); however, this was not reflected by veterinarians working in Spain (51.7%).

CLINICAL SIGNIFICANCE

If cytology of canine mammary masses were able to differentiate between benign and malignant, most veterinarians in Italy, UK and Greece would utilise the technique, justifying further research into the diagnostic accuracy of this test. Spanish veterinarians were significantly different and further research into why these individuals would not value the ability of cytology to differentiate between benign and malignant may be of value.

Diagnostic Accuracy of a Direct Panfungal Polymerase Chain Reaction Assay Performed on Stained Cytology Slides

Molecular techniques are increasingly being applied to stained cytology slides for the diagnosis of neoplastic and infectious diseases. Such techniques for the identification of fungi from stained cytology slides have not yet been evaluated. This study aimed to assess the diagnostic accuracy of direct (without nucleic acid isolation) panfungal polymerase chain reaction (PCR) followed by sequencing for identification of fungi and oomycetes on stained cytology slides from dogs, cats, horses, and other species. Thirty-six cases were identified with cytologically identifiable fungi/oomycetes and concurrent identification via fungal culture or immunoassay. Twenty-nine controls were identified with no cytologically or histologically visible organisms and a concurrent negative fungal culture. Direct PCR targeting the internal transcribed spacer region followed by sequencing was performed on one cytology slide from each case and control, and the sensitivity and specificity of the assay were calculated. The sensitivity of the panfungal PCR assay performed on stained cytology slides was 67% overall, 73% excluding cases with oomycetes, and 86% when considering only slides with abundant fungi. The specificity was 62%, which was attributed to amplification of fungal DNA from control slides with no visible fungus and negative culture results. Direct panfungal PCR is capable of providing genus- or species-level identification of fungi from stained cytology slides. Given the potential of panfungal PCR to amplify contaminant fungal DNA, this assay should be performed on slides with visible fungi and interpreted in conjunction with morphologic assessment by a clinical pathologist.

Nonconformities in Veterinary Cytopathological Examinations: A Retrospective Study of Unsuitable Samples for Analysis

The aim of this study was to evaluate the main nonconformities that result in cytopathological samples inappropriate for diagnosis in veterinary medicine. All cytopathological samples, obtained from different canine and feline tissues/lesions, included in the study were received and classified as inconclusive by a single public laboratory of veterinary pathology, located in Pernambuco State, Brazil, between 2012 and 2016. Nonconformities regarding the smear quality, cellularity, presence or absence of hemorrhage, cellular overlapping, desiccation, and presence or absence of necrotic debris and/or artifacts were evaluated. Data were tabulated using Microsoft Excel 2007; absolute and relative frequencies were calculated using EPIINFO 3.5.2. From the 3268 cases received between 2012 and 2016, 190 cases were selected and comprised 514 inconclusive slides. The most frequent nonconformities detected were insufficient/absence of cellularity in 100% (514/514), inadequate submacroscopic presentation in 87% (446/514), and hemorrhage in 69% (356/514) of samples. Other features identified were cellular overlapping in 34% (175/514), inadequate staining in 31% (175/514), artifacts in 30% (154/514), desiccation in 28% (145/514), and necrotic debris in 26% (133/514) of samples. The implementation of laboratory standard operational procedures aimed at maintaining quality is essential. It is necessary to initially identify the main errors occurring in the processing stages as a way to guide and design strategies to avoid them.

All lesions great and small, part 2. Diagnostic cytology in veterinary medicine

This is the second in a two‐part review of diagnostic cytopathology in veterinary medicine. As in human medicine, cytopathology is a minimally invasive, rapid, and cost‐effective diagnostic modality with broad utilization. In this second part, the diagnostic applications of cytology in respiratory, gastrointestinal, genitourinary, endocrine, ocular, and central nervous system tissues are discussed with a section describing fluid analysis in veterinary medicine. As noted in the previous manuscript, which characterized the cytology of the skin/subcutis, musculoskeletal, and lymphoid tissues, the interpretation of veterinary cytology samples must be undertaken with extensive knowledge of the breadth of animal species, including familiarity with the frequency and clinical progression of diseases, both of which can be influenced by species, breed, and husbandry conditions. Similar to part one, this review focuses on the most common domestic companion animal species (dog, cat, and horse) and highlights lesions that are either unique to veterinary species or have relevant correlates in people. The cytologic features and biological behavior of similar lesions are compared, and selected mechanisms of disease and ancillary diagnostics are reviewed when appropriate. Supporting figures illustrate a subset of lesions. While not an exhaustive archive of veterinary cytology, the goal is to give cytopathologists working in human medicine a general impression of correlates and unique entities in veterinary practice. Diagn. Cytopathol. 2014;42:544–552. © 2014 Wiley Periodicals, Inc.

Histomorphological and immunohistochemical characterization of 172 cutaneous round cell tumours in dogs

This paper describes the use of a panel of antibodies (CD117, CD3, CD79a, CD45, cytokeratin, vimentin and E-cadherin) on formalin-fixed, paraffin-embedded sections of canine cutaneous round cell tumours. Neoplastic tumours were diagnosed by histology and histochemical stains and included 107 mast cell tumours, 31 cutaneous histiocytomas, two localized histiocytic sarcomas, 21 cutaneous lymphomas, three plasma cell tumours, one transmissible venereal tumour and seven unclassified round cell tumours. The histologic diagnosis was modified in 39.5% of the total 172 neoplasms. The staining for CD45 and Ecadherin were variable, and therefore, the final diagnoses of cutaneous histiocytoma and localized histiocytic sarcoma were made based on histology in association with negative results for CD3, CD79a, CD117 and cytokeratin. The cellular origin of unclassified round cell tumours was defined in all cases. Cutaneous B-cell lymphoma and plasma cell tumours were CD79a-positive and could be distinguished from each other by the morphological characteristics. Mast cell tumours and T cell lymphoma were CD117 and CD3 positive, respectively. The positive staining for vimentin and the negative staining for CD3, CD79a, CD117 and cytokeratin favoured the diagnosis of transmissible venereal tumours. Thus, the final diagnosis of cutaneous round cell tumours should be based on the interpretation of immunohistochemical results together with the cellular morphology observed by histology. Therefore, more studies to optimize the specific markers in formalin-fixed, paraffinembedded tissues (especially for histiocytes) are required for definitive diagnosis of round cell tumours in dogs.

Utility of nuclear morphometry in the cytologic evaluation of canine cutaneous soft tissue sarcomas

Cytopathologists lack reliable criteria to distinguish neoplastic from reactive spindle cells; however, with computer-based nuclear morphometry, it is now possible to more objectively and precisely quantify differences between selected populations of cells. Forty-four cutaneous soft tissue sarcomas and 5 cases of reactive spindle cell proliferations in the dog were morphometrically analyzed with regard to median and standard deviation (SD) of nuclear area, diameter (max, min, mean), radius (max, min), perimeter, and roundness. Overall, nuclei from reactive spindle cells were larger, with greater variation in nuclear size and shape. Significant differences ( P < 0.05) were found for several nuclear parameters, including the median and SD of maximum diameter and radius, as well as the SD of roundness. No significant differences were found in nuclear parameters between soft tissue sarcomas divided by histologic grade, mitotic index, or tumor necrosis score. Analysis of the sources of variation indicated near-perfect intraobserver and substantial interobserver agreement. The largest source of variation was due to selection of different measurement fields, reflecting the inherent biological variation in nuclear size within the tumor cell population. The results indicate that nuclear morphometry on cytologic preparations is a reproducible method that may be able to differentiate cutaneous soft tissue sarcomas from reactive mesenchymal lesions in the dog. Further studies, including a larger number of cases, are warranted to assess repeatability of results.