Testicular Tumor (Seminoma) in Cats

By PetMD Editorial on Apr. 19, 2010

Seminoma in Cats

Seminoma is a benign (not recurrent or progressive), unilateral tumor of the testis that is extremely rare in male cats (one case of malignant tumor with metastasis has been reported. Typically measuring less than two centimeters in diameter, a seminoma often causes no clinical symptoms in the affected cat and is therefore difficult to identify.

Symptoms and Types

Although seminomas rarely causes any clinical symptoms in the animal, some cats exhibit pain due to pressure from the growing tumor. In a few cases, the testicular mass can be palpapated. Even rarer still, some tumors can become malignant and metastasize to other parts of the body.


Seminomas develop due to cryptorchidism, a fetal abnormality which occurs when one or both testes fail to descend into the scrotum from where they develop in the abdomen.


Your veterinarian will perform a thorough physical examination, searching for a testicular mass and whether or not it is palpable. Cats with a seminoma may exhibit pain or abnormally large testis. Typically, laboratory tests such as complete blood count, biochemistry profile, and urinalysis are within normal ranges, although an ultrasound of the testicular tissue may reveal a mass. In these cases, your veterinarian may recommend performing a tissue biopsy of the testicular mass for further evaluation. If this is not possible, castration may be required to confirm the diagnosis.



Removal of the tumor is the treatment of choice, which is best accomplished by castrating the cat. If the tumor is cancerous or has metastasized to other parts of the body, however, your veterinarian may recommend chemotherapy.

Living and Management

In general, the overall prognosis of cats that undergo castration is excellent. But this is dependent on the whether the tumor is benign or malignant.  

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