# Teratoma of the Testis

> Teratoma of testis for NEET-PG Surgery: benign prepubertal versus malignant postpubertal types, mature and immature, post-chemotherapy residual masses.

- Canonical URL: https://prepelephant.com/topics/neet-pg/surgery/teratoma-testis
- Exam / course: NEET-PG · Subject: Surgery
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Teratoma of the Testis", PrepElephant, https://prepelephant.com/topics/neet-pg/surgery/teratoma-testis

## 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.