A 16-year-old girl from Mumbai presents to the emergency department with acute severe left lower abdominal pain and nausea for 6 hours. On examination, she is in distress with a rigid, tender left lower abdomen and guarding. Pelvic ultrasound reveals a 15 cm left ovarian mass with internal hemorrhage and free fluid in the pelvis. Serum AFP is 2,200 ng/mL (normal <10), β-hCG is 12 mIU/mL (normal <5), and hemoglobin is 9.2 g/dL. Emergency left oophorectomy is performed. Histopathology shows sheets of cuboidal cells with hyaline globules, microcystic pattern, and areas of hemorrhage and necrosis. What is the most likely diagnosis?

Explanation

## Diagnosis: Yolk Sac Tumor (Endodermal Sinus Tumor) ### Clinicopathologic Correlation **Key Point:** The combination of: 1. **Elevated AFP alone** (2,200 ng/mL) with normal/borderline β-hCG 2. **Histologic hallmark: hyaline globules** (periodic acid–Schiff [PAS]-positive, diastase-resistant) 3. **Microcystic pattern** with cuboidal cells 4. **Acute hemorrhage and necrosis** (clinical presentation: torsion with infarction) ...is pathognomonic for yolk sac tumor. ### Pathology Pearls **High-Yield:** Yolk sac tumor (endodermal sinus tumor) is the most common malignant ovarian germ cell tumor in children and young adolescents. It arises from primitive endoderm and recapitulates embryonic yolk sac structures. #### Histologic Features | Feature | Characteristic | This Case | |---------|---------------|-----------| | **Hyaline globules** | PAS+ intracellular/extracellular spheres | Present (diagnostic) | | **Microcystic pattern** | Small cysts lined by cuboidal epithelium | Present | | **Schiller-Duval bodies** | Papillary structures with central vessel (pathognomonic) | May be present | | **Cuboidal epithelium** | Low columnar to cuboidal cells | Present | | **Necrosis/hemorrhage** | Common due to rapid growth and torsion | Present | **Mnemonic:** **YOLK SAC = Youthful, Ovarian, Lining (endoderm), Keratinoid globules, Schiller-Duval bodies, Acute hemorrhage/torsion, Cuboidal epithelium, Elevated AFP** ### Tumor Marker Profile **Clinical Pearl:** Yolk sac tumor produces **AFP exclusively** (from visceral endoderm). β-hCG remains normal or only mildly elevated (unless there is a concurrent trophoblastic component, which would make it a mixed tumor). In this case, β-hCG = 12 (borderline normal) confirms yolk sac tumor as the sole component. ```mermaid flowchart TD A["Young woman with ovarian mass"]:::outcome --> B{"Tumor markers?"}:::decision B -->|"Both β-hCG + AFP high"|C["Mixed germ cell tumor"]:::outcome B -->|"AFP high only"|D["Yolk sac tumor"]:::outcome B -->|"β-hCG high only"|E["Choriocarcinoma"]:::outcome B -->|"Both normal"|F{"Histology?"}:::decision F -->|"Uniform sheets of cells"|G["Dysgerminoma"]:::outcome F -->|"Immature teratoid elements"|H["Immature teratoma"]:::outcome ``` ### Clinical Context: Acute Presentation The acute hemorrhage and free fluid reflect **ovarian torsion** — a common complication in young women with large germ cell tumors. The rapid growth and friability of yolk sac tumors predispose to torsion and infarction, explaining the emergency presentation. ### Prognosis and Management **High-Yield:** Yolk sac tumors are chemotherapy-sensitive. With BEP (bleomycin, etoposide, cisplatin) chemotherapy, 5-year survival is >90% even for advanced stages. Fertility-sparing surgery (unilateral oophorectomy) is standard in young women.