5-year-old male intact German Shepherd Dog – American College of Veterinary Radiology

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Ultrasound image of a caudal abdominal mass (scroll right for other still images)
Color Doppler on the mass
Urinary Bladder
Prostate

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5-year-old, male, German Shepherd Dog presented for a 6-week history of gynecomastia and hyporexia.
The patient had a previous history of unilateral cryptorchidism and was neutered, but it was unknown if the retained testicle was successfully removed.
On physical exam, there was a large (grapefruit-sized) firm mass within the caudal abdomen, a pendulous prepuce, mild gynecomastia, and alopecia and mild hyperpigmentation of the hindlimbs.
Hematology revealed a neutrophilic leukocytosis (17.8K) and monocytosis (1.2K). A chemistry panel showed no significant findings.
An abdominal ultrasound was performed for further evaluation.

There is a large, heterogeneous, mixed echogenicity mass with internal cavitation located in the caudal abdomen immediately cranial to the urinary bladder.
Along the cranioventral margin of the mass, there are hypoechoic to anechoic tubular structures that display intermittent Doppler signal upon interrogation, consistent with the vasculature of the pampiniform plexus.
There is partial twisting of this vasculature, and in the mesentery adjacent to the mass, the soft tissues have a whirl pattern (‘whirl sign’) with curvilinear/whirling Doppler signal.
The prostate is markedly symmetrically enlarged with undulant margins and the parenchyma is diffusely heterogenous with multiple small anechoic cysts.
The urinary bladder is mild to moderately distended and contains a large volume of suspended echogenic debris

Large caudal abdominal mass, most consistent with a cryptorchid neoplastic testicle. Given history, a Sertoli cell tumor is the primary differential diagnosis, with other testicular neoplasms considered less likely.
The whirl sign at the cranial aspect of the mass is indicative of torsion.
Marked prostatomegaly and heterogeneity may be secondary to squamous metaplasia and/or hypertrophy associated with #1. Given suspicion of underlying cystitis, concurrent prostatitis is also possible.
Urinary bladder debris, likely secondary to cystitis.

Exploratory laparotomy was performed and confirmed a cryptorchid testicular mass with marked torsion. The mass was removed and a biopsy of the prostate gland was performed.

Histopathology of the testicle showed both a Sertoli cell tumor and seminoma with invasion of neoplastic Sertoli cells into blood vessels and lymphatics. Prostatic histopathology revealed squamous metaplasia secondary to feminization syndrome from the Sertoli cell tumor.

Cystitis was confirmed via urinalysis and urine culture. No evidence of prostatitis was identified. The patient was treated with antibiotics for the urinary tract infection and was subsequently started on carboplatin chemotherapy.

Intra-operative photograph of the retained, torsed testicle

Discussion

In dogs diagnosed with testicular neoplasia, anywhere from 4-20% of cases will have multiple primary tumors, as seen in this case. Specifically, cryptorchid testicles have an increased risk of developing seminomas and Sertoli cell tumors. Feminization is a common paraneoplastic syndrome seen with Sertoli cell tumors. Clinical signs of feminization include gynecomastia, bilateral symmetric alopecia with hyperpigmentation, a pendulous appearance to the prepuce, and prostatomegaly, as seen in this case.

Less common but important clinical manifestations include bone marrow suppression and testicular torsion. Sertoli cell tumors and seminomas rarely exhibit regional or distant metastasis, though local invasion is common.

Surgical excision is generally curative, however given the evidence of vascular and lymphatic invasion in this case, post-operative chemotherapy was recommended.

Testicular torsion is generally associated with neoplasia in dogs, with increased risk with large tumors. Sonographic features of torsion include significant enlargement (6-15 cm), altered parenchymal echogenicity, and decreased to absent blood flow. In this case, a ‘whirl’ sign was appreciated, further supporting a diagnosis of testicular torsion. The ‘whirl’ or ‘whirlpool’ sign represents the twisting of vasculature and has been described both on ultrasound and computed tomography as a strong indicator of torsion of multiple different organs. In human literature, detection of the ‘whirl’ sign is a reliable method for diagnosing testicular torsion in pediatric and adult males, and the ‘whirl’ sign has been reported in a dog with torsion of a cryptorchid testicular neoplasm on computed tomography previously. This case provides a sonographic example of the ‘whirl’ sign in a case of a torsed neoplastic cryptorchid testicle.

References

Hayes, H.M., Jr. and T.W. Pendergrass, Canine testicular tumors: epidemiologic features of 410 dogs. Int J Cancer, 1976. 18(4): p. 482-7.
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