PART I – The Male Reproductive Tract

I. Indications for biopsy/pathological evaluation

The male reproductive tract comprises two testes, each with epididymis, spermatic cord and ductus (vas) deferens; penis; prepuce; and prostate gland, the only accessory sex gland in the dog. Histopathological evaluation of the male reproductive tract may be required for the following reasons:

a) Abnormalities detected at time of neutering.
b) Concern regarding neoplasia, cysts or other mass effects detected clinically.
c) Investigation of abnormal haemorrhage or discharge from the penis or prepuce.
d) Investigation of potential hormonal abnormalities (e.g. alopecia or gynaecomastia).
e) Prostate gland: Biopsy is indicated when less invasive diagnostic techniques have not reached a diagnosis; when there is no response to initial treatment; or where rapid diagnosis is required to allow swift therapy1

II. Different types of biopsy

Image adapted from: https://commons.wikimedia.org/wiki/File:Male_repro_system_labelled.jpg

 *It’s not necessary to send scrotal skin unless you have a concern about a scrotal lesion.  However, if you are interested in scrotal lesions, particularly potential neoplasms, you could you consider inking the margins (see Finn fact sheet 102).

III. How to sample and send reproductive tract samples

Testes/epididymis and spermatic cord/pampiniform plexus

  • Testes (which will include epididymis), with attached spermatic cord and pampiniform plexus, should be fixed in 10% neutral buffered formalin.
  • After neutering, testes and spermatic cord can be sent in their entirety for histopathology. It is best to avoid cutting into the tissues. 
  • Sending en bloc, rather than submitting only slices of testis, ensures that the spermatic cord and pampiniform plexus are included, although you may wish to send left and right sides separately if distinguishing between the two is important clinically. The pampiniform plexus and spermatic cord are important to ensure there is no ascending spread of any lesions towards the peritoneal space, particularly neoplasms. We always evaluate these histologically if included.

Prostate gland

A few diagnostic methods are used to assess canine prostatic gland, but biopsy is the gold standard and achieves a diagnosis in approximately two thirds of cases3. Sampling may be surgical or percutaneous1,4. Biopsies may be Tru-cuts or wedge resections and there are some advantages and disadvantages to be aware of, outlined in Fig 1. Main contraindications to prostatic biopsy are acute prostatitis and potential prostatic abscess1.

Fig 1.  Pros and Cons of Tru-cut prostatic biopsies

IV. Relevant clinical information

a) Signalment: Reproductive neoplasia is more likely in older animals so the age of the animal is helpful.
b) Brief summary of clinical signs and reason for sampling.
c) Results of any other tests.
d) Consider taking photographs at time of sampling as colours and textures change with fixation.

V. Diagnoses in male reproductive tract submissions

The more common testicular diseases are cryptorchidism, neoplasia and inflammation (orchitis and epididymitis). Spermatic cord torsion is uncommon but can occur in conjunction with testicular neoplasia. Inflammatory diseases are more commonly seen in younger dogs while neoplasia is more common in older dogs. Prostatic disease is common in the dog but rare in the cat. More common conditions include benign prostatic hyperplasia, prostatitis, prostatic cysts, or neoplasia, particularly prostatic adenocarcinoma5.

VI. Histopathology of male reproductive tract lesions

This section includes examples of the more common lesions we see.

Fig 2: Testicular seminoma. This presents as solid sheets of atypical cells reminiscent of a round cell tumour. Inset: Higher power highlights atypical germ cells with one atypical mitotic figure (yellow arrow). Grossly, these tumours are often off-white, soft and slightly bulging on cut section.

Fig 3. Sertoli cell tumour. Composed of supportive cells from the seminiferous tubules. Approximately 20-30% of affected dogs manifest signs of feminization due to hyperoestrogenism. The majority of Sertoli cell tumours are benign – metastasis is more likely to occur with larger tumours, and involves the sublumbar and pelvic lymph nodes, with potential dissemination to various internal organs.

Fig 4. Sertoli cell tumour. The arrangement is more tubular, or at least distinct nesting, rather than sheets, with palisading on the basement membrane (yellow arrow). The cells are also spindle shaped or elongated rather than round.  Grossly, these tumours are white and firmer than seminomas due to more abundant stroma.

Fig 5. Prostate gland. This is histologically normal but, as the prostate gland was visibly enlarged, the changes are consistent with benign prostatic hyperplasia.

Reference

  1. Smith (2008) Canine prostatic disease: A review of anatomy, pathology, diagnosis, and treatment. Theriogenology 70:375-383.
  2. https://www.finnpathologists.com/wp-content/uploads/2023/11/FINN-FACT-SHEET-10-Inking-Issue-3-14.11.2023.pdf
  3. Kustritz (2006) Collection of tissue and culture samples from the canine reproductive tract. Theriogenology 66:567–74.
  4. Holak et al (2010) Laparoscopy-guided prostate biopsy in dogs – a study of 13 cases. Polish Journal of Veterinary Sciences 13:765-766.
  5. Chaudhary et al (2024) Chapter 11: Diseases of the reproductive system of male dogs and cats. In: Introduction to Diseases, Diagnosis, and Management of Dogs and Cats.

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