Mammary Cytology can be a Real Pain

This case is a prime example of how unreliable mammary mass cytology can be.

A 13 year old female, spayed dog was seen by her vet for a mass on her ventrum which turned out to be coming from the mammary gland.

The vet aspirated it, and this is what I saw in the first photo. Epithelial clusters, but they don’t look all that atypical right? You might assume they are benign then right? 


An abdominal ultrasound was done. The iliac lymph node was enlarged and aspirated. The FNA from the iliac lymph node showed tons of similarly appearing epithelial cells. Even though they don’t look atypical in the node either, they shouldn’t be in a node! So, we know they are inherently malignant. 

So, now knowing the iliac lymph node is effaced, we then can go back to the mammary mass and safely assume this population, despite being boring on cytology, is malignant.