A 22-year-old nulliparous woman from rural India presents with a 6-week history of abdominal pain and vaginal bleeding. Pelvic examination reveals a firm, fixed lower abdominal mass. Serum AFP is 8,500 ng/mL and β-hCG is 1,200 mIU/mL. CT abdomen shows a 12 cm left ovarian mass with areas of necrosis and haemorrhage. Histopathology of the surgical specimen shows cuboidal cells with clear cytoplasm, forming endodermal structures (glandular and tubular patterns), with prominent mitotic activity. What is the most likely diagnosis?

Explanation

## Diagnosis: Yolk Sac Tumour (Endodermal Sinus Tumour) ### Histopathological Hallmark **Key Point:** The description of **cuboidal cells with clear cytoplasm forming endodermal structures (glandular and tubular patterns)** is pathognomonic for yolk sac tumour. ### Diagnostic Features | Feature | Yolk Sac Tumour | Embryonal Carcinoma | Immature Teratoma | |---------|-----------------|---------------------|-------------------| | **Histology** | Cuboidal cells, endodermal differentiation, glandular/tubular patterns | Primitive pluripotent cells, embryonic disc-like structures | Immature neural, epithelial, mesenchymal tissues | | **AFP elevation** | Marked (often >1,000 ng/mL) | Mild to moderate | Variable (usually <100 ng/mL) | | **β-hCG** | Absent or minimal | Moderate elevation | Absent or minimal | | **Schiller-Duval bodies** | Pathognomonic (papillary structures with central vessel) | Absent | Absent | | **Age** | 5–30 years (peak 10–20) | 10–30 years | 10–30 years | | **Prognosis** | Good with chemotherapy | Intermediate | Depends on grade | ### Clinical Correlation **High-Yield:** Yolk sac tumour is the **most common malignant ovarian germ cell tumour in children and adolescents** (accounts for ~40% of malignant germ cell tumours). 1. **Age 22 years** → Within typical age range for yolk sac tumour 2. **Markedly elevated AFP (8,500 ng/mL)** → Characteristic of yolk sac tumour; produced by endodermal cells 3. **Mild β-hCG elevation (1,200 mIU/mL)** → Suggests minor trophoblastic component or contamination; not the primary marker 4. **Histology: endodermal differentiation** → Yolk sac tumours recapitulate yolk sac endoderm 5. **Necrosis and haemorrhage** → Rapid growth and aggressive behaviour typical of malignant germ cell tumours ### Pathological Features of Yolk Sac Tumour **Mnemonic: "YOLK"** - **Y**olk sac origin → Endodermal differentiation - **O**utstanding marker → AFP (often >1,000 ng/mL) - **L**ow age → Peak 10–20 years - **K**ey structure → Schiller-Duval bodies (papillary cores with central vessel) ### Schiller-Duval Bodies - Pathognomonic papillary structures with a central blood vessel - Resemble primitive glomeruli - Not always present but highly specific when found **Clinical Pearl:** Yolk sac tumours are highly chemotherapy-responsive. With modern BEP (bleomycin, etoposide, cisplatin) chemotherapy, 5-year survival exceeds 90% even in advanced stages. Fertility-sparing surgery followed by adjuvant chemotherapy is the standard of care in young women. ### Treatment Algorithm ```mermaid flowchart TD A[Yolk Sac Tumour Diagnosed]:::outcome --> B[Fertility-sparing surgery?]:::decision B -->|Yes, young woman| C[Unilateral oophorectomy + staging]:::action B -->|No, older/multiparous| D[TAH-BSO + staging]:::action C --> E[Adjuvant BEP chemotherapy]:::action D --> E E --> F[Excellent prognosis with chemotherapy]:::outcome ``` [cite:Robbins 10e Ch 22]