Teratoma of the Testis
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Direct answer
Teratoma contains tissue from more than one germ layer — cartilage, glandular epithelium, muscle, neural elements — and its behaviour depends entirely on puberty. In a prepubertal boy, teratoma is benign regardless of immaturity, and inguinal orchidectomy (or even testis-sparing excision in selected centres) is curative with no staging required. After puberty, every teratoma carries malignant potential, is treated within the NSGCT framework, and — crucially — is resistant to chemotherapy and radiotherapy, which is why residual masses after chemotherapy are surgically resected rather than observed.
What you must remember
- Prepubertal mature and immature teratomas are benign; postpubertal teratomas are malignant germ cell tumours despite a mature appearance.
- Immature teratoma contains primitive neuroectodermal or blastematous elements; "mature" does not mean harmless after puberty.
- Teratoma plus yolk sac tumour is the dominant paediatric combination; pure teratoma is the next commonest childhood testicular tumour.
- Teratoma is chemoresistant and radioresistant — the key fact governing post-chemotherapy surgery.
- Growing teratoma syndrome: normalised markers but an enlarging mass during chemotherapy, demanding excision.
- Malignant transformation of teratoma produces somatic cancers (adenocarcinoma, sarcoma) with correspondingly worse prognosis.
- Post-chemotherapy residual retroperitoneal masses over about 1 cm are resected by retroperitoneal lymph node dissection; histology shows necrosis, teratoma or viable cancer in roughly equal thirds in classic series.
Worked example: the residual mass after chemotherapy
A 30-year-old with mixed germ cell tumour (embryonal carcinoma plus teratoma) completes four cycles of BEP for para-aortic nodal disease. Markers have normalised. The repeat CT shows a residual 3 cm retroperitoneal mass.
The reasoning walks like this. First, normalised markers mean active chemotherapy-responsive disease has been killed, but the mass itself is unchanged in principle — teratoma does not melt with cisplatin. Second, leaving it in situ risks growth (growing teratoma syndrome), local invasion, later malignant transformation into adenocarcinoma or rhabdomyosarcoma, and a far harder delayed operation. Third, the correct move is post-chemotherapy retroperitoneal lymph node dissection, ideally when markers are normal and within a window after chemotherapy. Fourth, the histology then drives further treatment: necrosis/fibrosis means observation; teratoma means surveillance; viable cancer beyond 10 per cent of the mass means salvage chemotherapy. That three-way pathological split is the examinable heart of post-chemotherapy surgery.
Contrast the child. A four-year-old with a cystic-solid testicular mass and normal AFP undergoes orchidectomy showing pure immature teratoma. No CT, no markers beyond age-adjusted AFP, no chemotherapy — the tumour is benign, and surveillance is clinical. Writing the adult algorithm for a child, or reassurance for an adult, is how viva candidates invert the two scenarios.
Where students slip
The phrase "mature teratoma, therefore benign" is the single most punished sentence here once the patient is postpubertal. Maturity describes the tissue, not the biological contract; postpubertal teratomas metastasise like other NSGCTs. The second slip is expecting chemotherapy to clear teratoma — a persistent mass with perfect markers is not treatment failure, it is teratoma being teratoma, and the answer is a knife. Third, candidates forget that "growing teratoma syndrome" occurs with normal markers; a growing mass with rising markers instead means resistant viable cancer.
Frequently asked questions
Is immature teratoma of the testis malignant?
Before puberty, no — it is benign and orchidectomy cures. After puberty, immature (and mature) teratomas are treated as malignant NSGCT regardless of how well differentiated they appear.
Why are residual masses resected after chemotherapy for NSGCT?
Because teratoma is chemoresistant. Residual masses over about 1 cm may contain necrosis, teratoma or viable cancer, and only resection with histology separates them and prevents later growth or malignant transformation.
What is growing teratoma syndrome?
Enlargement of a metastatic mass during or after chemotherapy despite normal tumour markers, due to proliferating teratoma; it mandates surgical excision, not more chemotherapy.
Can teratoma turn into another cancer?
Yes — malignant somatic transformation can produce adenocarcinoma or sarcoma within teratoma, which then demands management of the transformed histology.
What is the most common testicular tumour combination in children?
Teratoma with yolk sac elements, followed by pure teratoma and pure yolk sac tumour; seminoma is essentially a postpubertal tumour.