Penile cancer: causes and pathogenesis

Causes of penile cancer

The exact causes of penile cancer are not fully established. It is known that chronic irritation of the skin of the preputial sac by the smegma and the products of the bacterial decomposition of the depleted epithelial cells plays a negative role, therefore, the probability of developing penile cancer is lower in men subjected to circumcision than in men with preserved foreskin. This is most evident in phimosis, when the smegma accumulates in significant quantities and chronic inflammation is more pronounced. Thus, in patients with penile cancer, phimosis is found in 44-90% of cases

Long-term exposure to smegma affects the likelihood of developing penile cancer, as indicated by the varying incidence of the disease, depending on cultural and religious practices in different countries. For example, among Jewish men who, for religious reasons, are usually circumcised on the 8th day after birth, cancer of the penis is extremely rare. However, among Muslims who are circumcised at an older age, the cancer of the penis is observed in the bowl. It should be noted that circumcision in adults does not reduce the risk of developing the disease.

There are a number of precancerous diseases. They include:

• diseases sporadically associated with penile cancer (skin horn, bovenoid papulosis);
• diseases with a high risk of developing into cancer (leukoplakia, xerosal obliterating balanitis, genital warts, Buschke-Levenshtein tumor, Keira erythroplasia).

Data on the possible involvement of the human papillomavirus in the etiopathogenesis of penile cancer have been obtained. A number of authors believe that infection with human papillomavirus type 16 and 18 leads to the development of tumors: they are found in 60-80% of patients with malignant neoplasms of the penis. The carcinogenic effect of these viruses is associated with the inactivation of tumor gene-suppressor p53 and pRb by the viral proteins E6 and E7, respectively. However, there are no convincing data confirming the reliability of this theory.

[1], [2], [3], [4]

Morphology of penis cancer

Cancer of the penis in 95% of cases is squamous keratinized (91.3%) or non-keratinizing (8.7%) cancer.

There are various morphological forms of squamous cell carcinoma of the penis.

By type of growth:

• classical squamous cell;
• basal cell;
• Verrux and its varieties:
• sarcomatoid;
• adenoskvamoznaya.

By the nature of growth:

• with superficial distribution;
• with nodular or vertical growth;
• verrucous.

By degree of differentiation:

• highly differentiated;
• moderately differentiated;
• low-differentiated;
• undifferentiated.

It was found that at low and moderately differentiated forms of cancer at the time of diagnosis, almost all patients already have metastases to the lymph nodes. With highly differentiated tumors, lymph nodes are affected in 50% of cases.

The incidence of cancer in the region of the glans penis, foreskin to the body is 85.15 and 0.32%, respectively. More frequent tumor localization in the head and foreskin area is associated with constant contact of the skin with the smegma and the products of decay of the ejaculated epithelial cells.

For cancer of the penis is characterized by lymphogenous metastasis in the inguinal and ilium lymph nodes. Hematogenous metastases appear in the late stages of the disease and can affect the lungs, liver, bones, brain, heart. Outflow of lymph from the penis occurs in the superficial and deep inguinal and pelvic lymph nodes. Surface inguinal nodes in the amount of 4-25 lie in the Scarpa triangle on the surface of the deep fascia and along the large saphenous vein. The sentinel node is located medial to the femoral vein. Deep inguinal nodes, number from one to three, lie under the wide fascia also medial to the femoral vein. In view of the strong development of the lymphatic network, metastasis of the groin areas of both sides is possible. Lymph from the base of the penis flows through the vessels of the femoral canal into the external iliac and pelvic lymph nodes. It should be borne in mind that the appearance of palpable dense regional lymph nodes does not always indicate their metastatic lesion and may be associated with inflammatory changes. That is why many authors emphasize that a clinical examination does not allow to establish reliably the degree of involvement of lymph nodes in the tumor process. Thus, inguinal lymph nodes can palpate in 29-96% of patients with penile cancer. In 8-65% of cases, morphological examination of lymph nodes shows no signs of metastatic lesion. On the other hand, in 2-66% of patients with non-significant inguinal nodes after microscopic lymphadenectomy, micrometastases are detected.