Splenic nodule cytology matched histopathology in only about 55-67% of dogs

Earlier studies reported cytology accuracy anywhere from 59% to 92%, but those studies included dogs with diffuse splenomegaly. Corresponding author Janet Grimes, DVM, MS, DACVS, of the University of Georgia, said diffuse disease tends to make aspirates more accurate because the needle is more likely to sample the active process.

This study left out splenomegaly on purpose. It looked only at masses and nodules, which Grimes said are the cases where decisions and owner conversations are hardest. The agreement rate was lower than in some earlier studies but still within the published range.

Grimes said that for larger incidental masses, she recommends splenectomy because of rupture risk, even when the lesion may be benign. For those dogs, the size of the mass matters more than the cytology result.

For smaller nodules, she said aspirates can help guide the next step. If cytology shows neoplasia, she recommends splenectomy. If cytology shows a non-neoplastic process such as extramedullary hematopoiesis, she still recommends active surveillance with abdominal ultrasound every 3 months. A stable nodule stays on monitoring, and a shrinking one suggests EMH or nodular hyperplasia. A growing nodule raises concern for hemangiosarcoma or rupture, and she said the balance of risk and benefit then favors splenectomy.

The results apply only to non-ruptured lesions, because the institution does not routinely aspirate ruptured splenic masses. 18 of the 33 dogs had multiple nodules, which made it harder to be sure the aspirated nodule matched the histopathology slide. The review also used archived slides, which may not show the whole lesion.