Faecal Occult Blood Test

Case of the Month (Emma Scurrell December 2013)

Leydig cell tumour

 A non-painful mass was detected in the left testicle of a 12-year-old male Labrador during a routine examination at the time of vaccination. The mass was aspirated and following the cytology results, castration was performed and the affected testicle submitted for histopathology.

Fig 1.  Cytology preparation : neoplastic cells can be seen palisading capillary vessels.

Fig 2.  Cytology preparation : neoplastic cells contain a moderate amount of pale blue cytoplasm that frequently contains small clear punctate cytoplasmic vacuoles.

Fig 3. On gross examination, the testis contains a discrete yellow-tan mass. The yellow colour of the tumour is related to the lipid-rich steroid production and is characteristic of a Leydig cell tumour. Areas of cystic cavitation (arrow) and haemorrhage are another common feature.   

Fig 4. Histopathology : H&E stained tissue section - the neoplastic cells resemble normal interstitial cells with abundant, finely granular eosinophilic cytoplasm.

Final Diagnosis

Leydig (interstitial) cell tumour


Leydig cell tumours are common tumours of the testis and may be solitary or multiple. These tumours arise from the interstitial cells of the testis which under normal conditions are responsible for androgen production. The vast majority of Leydig cell tumours are behaviourally benign and metastatic spread is exceptionally rare. Occasionally Leydig cell tumours may be hormonally active which results in concurrent prostatic and/or perianal gland hyperplasia. These changes usually regress following castration

Previous Monthly Cases

Hypertensive Retinopathy January 2010
FIP in a cat - uncommon presentation February 2010
Phaeohyphomycosis    March 2010 
Scleral Rupture April 2010
Canine and feline epulides May 2010
Erythema multiforme in a labrador retreiver June 2010
Keloidal fibrosarcoma in a labrador retreiver July 2010
Cutaneous epitheliotropic lymphoma  August 2010 
Benign cutaneous histiocytoma  September 2010 
Iridociliary adenoma October 2010
Proliferative thrombovascular necrosis of the pinnae November 2010
Signet-ring cell carcinoma in the stomach of a dog December 2010
Cutaneous infiltrative lipoma in a labrador January 2011

Tonsillar squamous cell carcinoma February 2011
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Haemophagocytic histiocytic sarcoma June 2011
Alternaria spp. infection in an immunocompromised dog July 2011
Ocular manifestation of lymphoma in a cat  August 2011
Kerion dermatophytosis in a Cocker spaniel September 2011
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Malignant transformation of a viral papilloma in a dog  December 2011
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Fungal keratitis and secondary endophthalmitis in a horse November 2012
Myeloid leukaemia with lymph node invasion in a dog    December 2012
Cutaneous toxoplasmosis in a cat   January 2013
Glomerulonephritis in a dog  February 2013
Splenic mast cell tumour in a cat  March 2013
Laryngeal rhabdomyoma in a dog  April 2013
Mycobacterial infection in an eye May 2013
Key Gaskell syndrome in a cat June 2013
Intraosseous epidermoid cyst in the toe of a dog July 2013
Septic Lens Implantation Syndrome August 2013
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October 2013
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Faecal Occult Blood Test