Previous studies have shown a wide range of diagnostic accuracy of cytology in comparison to histopathology for splenic masses in dogs (59% to 92%), thus, a recent study published in JAVMA evaluates the correlation between cytology and histopathology results for these patients.
The authors retrospectively reviewed the medical records from 33 dogs that had a splenic mass or nodule and cytologic and histopathologic evaluation within 90 days of each other.
The results indicated agreement between cytology (via ultrasound-guided fine-needle aspirate) and histopathology (via splenectomy or necropsy) on diagnosis of neoplastic versus nonneoplastic conditions in 55% to 67% of dogs and disagreement in 24% of dogs with splenic masses or nodules. (The range of agreement is attributed to 7 dogs in which a definitive diagnosis was not given by cytology; thus, agreement could not be fully evaluated.) These findings reiterate that histopathology is the gold standard and should be recommended for a definitive diagnosis.
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We spoke with Janet Grimes, DVM, MS, DACVS, a professor of small animal surgery at University of Georgia College of Veterinary Medicine and the corresponding author for this study.
Q: The study advises that cytology cannot rule out a neoplastic condition but can be helpful in suggesting a neoplastic condition and therefore endorsing histopathology. How does this insight affect your clinical approach to dogs with splenic masses or nodules?
For dogs with incidentally identified (i.e., non-ruptured) splenic lesions, determining the optimal path forward can be challenging. For dogs with larger masses, splenectomy is indicated due to the risk for rupture, even with benign lesions. For those dogs, the size of the mass drives my clinical recommendation rather than a cytology result. For dogs with smaller splenic nodules, ultrasound-guided fine-needle aspirates can guide clinical decision-making. If cytology reveals neoplasia, splenectomy is indicated. However, if cytology indicates a non-neoplastic process (e.g., extramedullary hematopoiesis, or EMH), active surveillance is necessary because a non-neoplastic cytology result does not fully rule out underlying malignancy. Active surveillance should include an abdominal ultrasound every 3 months and decisions made on new findings:
- Static nodule: Continue monitoring with ultrasound.
- Regressing nodule: Indicative of EMH or nodular hyperplasia.
- Growing nodule: Recommend splenectomy.
A growing nodule may still be a non-cancerous lesion, but growth increases my concern for hemangiosarcoma or eventual rupture, even in the case of benign disease. Dogs with hemangiosarcoma diagnosed earlier in the disease course (i.e., lower stages) have increased survival rates compared to dogs with higher stages of hemangiosarcoma. Furthermore, splenectomy has minimal long-term complications. To me, the risk-reward balance is in favor of splenectomy in this case.
Q: This study solely includes dogs with splenic masses or nodular lesions; all previous studies have included dogs with splenomegaly. How do you think that affected your results?
Including cases of diffuse splenomegaly tends to increase the accuracy of cytology by increasing the probability of aspirating the active disease process. Also, the disease processes that lead to diffuse splenomegaly may be more amenable to diagnosis via cytology. We purposefully excluded splenomegaly and focused solely on nodular lesions. Although we did have a lower agreement rate than some studies, we were well within the previously published range, even when splenomegaly was included. As a surgeon, I am most frequently involved with mass-like lesions, where clinical decision-making and owner counseling remain difficult. I wanted to establish the true diagnostic utility of cytology specifically within the context of focal splenic masses.
Q: Beyond the broad differentiation of neoplastic versus non-neoplastic conditions, the study also evaluated the accuracy of cytology to diagnose the specific type of neoplasia. The type of neoplasia diagnosed (i.e., sarcoma versus lymphoma) differed between cytology and histopathology in 1 dog. What are your considerations when using cytology to diagnose the type of neoplasia?
With cytology, only a small portion of the lesion is evaluated, and tissue architecture is lost, giving histopathology a substantial diagnostic advantage. This specific case reinforces that the diagnosis may change once histopathologic evaluation is performed. It is important to counsel owners that clinical decisions are based on the best available presurgical information, but the final diagnosis and long-term prognosis may change once the entire tissue structure is evaluated.
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Q: What are the biggest limitations of the study?
First, our institution does not routinely aspirate ruptured splenic masses, so this information only applies to non-ruptured splenic lesions. Second, in dogs with multiple nodules (18 of 33 dogs in our study), retrospectively matching the aspirated nodule to the corresponding histopathology slide introduces potential discrepancy. Finally, although slide review by a pathologist was a strength of the study, we relied on archived slides, which typically represent the most diagnostic slide. This means the evaluated slide may not have fully reflected the entirety of the lesion.
Q: Is there anything you would like our readers to know that has not been mentioned?
I would emphasize that while a neoplastic cytology result is somewhat reliable for guiding surgical intervention, a non-neoplastic result should not provide false reassurance. Cytology can be a valuable initial screening tool, but histopathology following splenectomy remains the gold standard for definitive diagnosis of canine splenic masses.
Read the full story
Cytology and histopathology have poor to fair agreement for determination of neoplastic or nonneoplastic lesions in dogs with splenic masses or nodules.
Aluisio MF, Garner BC, Howerth EW, Laver T, Grimes JA. JAVMA | doi:10.2460/javma.26.01.0006