SN6 SHORT NOTE 5M

Define teratoma. Classify teratomas and describe the ovarian mature cystic teratoma.

Pathology · 2nd Professional — Para-Clinical

Definition

A teratoma is a tumour arising from totipotent germ cells, containing tissue derived from all three germ layers — ectoderm, mesoderm and endoderm.

Sites — gonads (ovary and testis), and midline extragonadal sites where germ cells arrest during migration: sacrococcygeal region, mediastinum, retroperitoneum, pineal
Sacrococcygeal teratoma is the commonest tumour of the newborn, arising from remnants of the primitive streak

Classification

Type	Features	Behaviour
Mature (benign)	Well-differentiated adult tissue — skin, hair, teeth, cartilage, thyroid, neural tissue	Benign in the ovary; the commonest ovarian tumour in young women
Immature	Contains embryonic or fetal tissue, especially primitive neuroepithelium	Malignant; graded by the amount of immature tissue
Monodermal (specialised)	Composed of one tissue — struma ovarii (thyroid tissue), carcinoid	Struma ovarii may cause thyrotoxicosis
Teratoma with malignant transformation	A somatic malignancy arising within a mature teratoma — usually squamous cell carcinoma	Malignant

CLINICAL PEARL

The same histology behaves entirely differently in the two sexes. A mature teratoma of the ovary is benign, whereas a teratoma of the adult testis is malignant whatever its degree of maturity, and metastasises. In the prepubertal testis, however, mature teratoma is benign. Age and site therefore matter as much as the histology.

Ovarian Mature Cystic Teratoma (dermoid CYST)

The commonest ovarian germ cell tumour; typically in women of reproductive age; bilateral in 10–15%
Naked eye — a unilocular cyst filled with sebaceous material and hair, with a rokitansky protuberance from which teeth and bone project
Microscopy — skin with adnexa, cartilage, bone, thyroid, respiratory and gastrointestinal epithelium, neural tissue
Complications — torsion (the commonest), rupture with granulomatous peritonitis, infection, and malignant transformation in about 1%

Testicular Germ Cell Tumours in Context

Tumour	Markers	Notes
Seminoma	HCG may be mildly raised; AFP is never raised	Radiosensitive; excellent prognosis
Yolk sac tumour	AFP	Commonest testicular tumour in children
Choriocarcinoma	HCG markedly raised	Highly aggressive; haematogenous spread
Embryonal carcinoma	AFP and hCG variable	Aggressive
Teratoma	AFP or hCG may be raised	Malignant in the adult testis

A raised AFP means the tumour is not a pure seminoma, however it looks under the microscope — the marker overrides the histology and changes treatment

Applied Aspects

Testicular tumours are among the most curable cancers, with over 90% cure even with metastases, because of their exquisite sensitivity to platinum-based chemotherapy
Markers are measured before and after orchidectomy, and their rate of fall guides further treatment
Sperm banking must be offered before chemotherapy
Ovarian dermoid cysts are usually managed by cystectomy, preserving ovarian tissue and fertility in young women
"Growing teratoma syndrome" — a mass enlarges during chemotherapy while markers fall, because chemotherapy kills the malignant elements and leaves mature teratoma behind; it requires surgical excision, not more chemotherapy

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