Seminoma

A seminoma is a germ cell tumour primarily found in the testicles, though it can occasionally occur in the mediastinum or other extra-gonadal locations. It is a malignant neoplasm that is highly treatable and curable, with a survival rate exceeding 95% if detected early.

Seminomas originate in the germinal epithelium of the seminiferous tubules and represent about half of all germ cell tumours of the testicles. Treatment often involves the removal of one testicle, but fertility and other sexual functions generally remain unaffected.

Signs and Symptoms

The typical age of diagnosis for seminoma is between 35 and 50 years, which is slightly older than for other germ cell tumours of the testes. In most cases, seminomas produce masses that can be felt during a testicular self-examination, though in up to 11% of cases, no mass is palpable, or testicular atrophy may occur. Testicular pain is reported in about 20% of cases. Low back pain may indicate metastasis to the retroperitoneum. Seminomas can also present as primary tumours outside the testis, most commonly in the mediastinum. In the ovary, these tumours are termed dysgerminomas, and in non-gonadal sites, particularly the central nervous system, they are called germinomas.

Diagnosis

Diagnosis typically involves imaging and blood tests. Ultrasound is often used to detect the presence of the tumour. Blood tests may reveal elevated levels of placental alkaline phosphatase (ALP) in 50% of cases, though ALP is not a specific marker for seminoma. Human chorionic gonadotropin (hCG) may be elevated due to the presence of trophoblast cells within the tumour. Lactate dehydrogenase (LDH) levels may also be elevated and have prognostic value in advanced cases.

Microscopically, seminomas are composed of sheet-like or lobular patterns of cells with a fibrous stromal network. The tumour cells typically have clear to pale pink cytoplasm and prominent nuclei. Focal lymphocyte inclusions in the fibrous septa and granulomas are common. The adjacent testicular tissue usually shows intratubular germ cell neoplasia and variable spermatocytic maturation arrest.

Treatment

Suspicious intratesticular masses detected via ultrasound should be managed with an inguinal orchiectomy. The pathology of the removed testicle and spermatic cord helps in staging the tumour. Tumours with both seminoma and nonseminoma elements, or those with elevated AFP, should be treated as nonseminomas. Abdominal CT or MRI scans and chest imaging are used to check for metastasis. Tumour marker analysis also assists in staging.

For Stage 1 seminoma, characterised by the absence of metastatic evidence, the preferred treatment is active surveillance involving periodic exams, tumour marker analysis, and radiographic imaging. Modern radiotherapy techniques and single-agent carboplatin cycles are also options but may have delayed side effects. The cure rate for stage 1 seminoma approaches 100%.

Stage 2 seminoma involves retroperitoneal metastasis and requires radiotherapy or combination chemotherapy. Large residual masses post-chemotherapy may necessitate surgical resection. Second-line treatments align with nonseminoma protocols.

Stage 3 seminoma, indicated by metastasis outside the retroperitoneum, is treated with combination chemotherapy. Second-line treatment follows protocols for nonseminomas.

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Self-assessment MCQs (single best answer)

What is the typical age range for the diagnosis of seminoma?

Which of the following is NOT a common site for primary seminoma outside the testis?

What percentage of seminoma cases present with testicular pain?

Which marker is elevated in approximately 50% of seminoma cases?

What is the first-line treatment for a suspicious intratesticular mass detected on ultrasound?

Which of the following is NOT typically part of the staging process for seminoma?

What is the cure rate for stage 1 seminoma?

What is the preferred treatment for stage 2 seminoma with retroperitoneal metastasis?

In the diagnosis of seminoma, which immunohistochemical markers are useful?

What histopathological feature is typical of seminoma?