Can Real-Time Cytology Reduce Biopsy Risk in Dogs and Cats? Evidence from Imaging-Guided Procedures

The Usefulness of Extemporaneous Cytological Examination in Imaging-Guided Biopsies

Andrea Rubini; Francesca Del Signore; Massimo Vignoli; Arianna Miglio; Martina Rosto; Andrea De Bonis; Rossella Terragni; Domenico Santori; Morena Di Tommaso

Background

Imaging modalities such as ultrasound and computed tomography are essential for identifying soft tissue and bone lesions in veterinary patients, but they cannot reliably distinguish inflammatory from neoplastic processes. Consequently, image-guided biopsies are frequently required to achieve a definitive diagnosis. However, biopsy procedures carry inherent risks, particularly in anatomically hazardous locations, and may require multiple tissue samples if initial specimens are non-diagnostic. Extemporaneous cytological examination—immediate microscopic evaluation of biopsy material—has been widely adopted in human medicine to assess sample adequacy, but its clinical utility in veterinary medicine has not been previously investigated.

Methods

This prospective study enrolled 79 animals (71 dogs and 8 cats) with soft tissue or bone masses undergoing ultrasound- or CT-guided biopsies between May 2021 and May 2022. Tru-cut needles were used for soft tissue lesions and bone needles for osseous lesions. Immediately after collection, tissue cores were rolled onto glass slides to prepare extemporaneous cytology, stained using May–Grünwald–Giemsa, and examined within 10–15 minutes to assess cellularity and provide a preliminary diagnosis when possible. All biopsy samples were subsequently submitted for histopathological examination, which served as the gold standard. Diagnostic accuracy and adequacy of cytology were statistically evaluated.

Results

Extemporaneous cytology demonstrated adequate, representative cellularity in 81.1% of cases, allowing clinicians to terminate the biopsy procedure without further sampling. The overall diagnostic accuracy of cytology compared with histopathology was 68.3%. When non-diagnostic samples caused by technical issues or lesion characteristics were excluded, diagnostic accuracy increased to 92.1%. Cytology showed particularly high diagnostic accuracy for lipomas, melanomas, and mast cell tumors, achieving full concordance with histology in these lesions. Most discrepancies occurred in poorly exfoliative tumors, blood-contaminated samples, or lesions with intrinsically low cellularity, such as fibrosis or necrosis.

Limitations

The study population was heterogeneous, including different species, lesion types, and anatomical locations, which may have influenced diagnostic performance. No direct comparison with other rapid on-site evaluation techniques was performed. Additionally, the technique requires the availability of trained personnel and appropriate laboratory infrastructure, limiting its applicability in all clinical settings.

Conclusions

Extemporaneous cytological examination during imaging-guided biopsies is a valuable adjunct in veterinary interventional diagnostics, providing real-time confirmation of sample adequacy and reducing the need for multiple biopsy attempts. While less definitive than histopathology, this method offers immediate feedback, demonstrates acceptable diagnostic accuracy, and may improve patient safety—particularly in high-risk biopsy locations. Histopathology remains the gold standard, but extemporaneous cytology represents a complementary tool that can enhance diagnostic efficiency in dogs and cats.

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