A 16-year-old girl is found to have a 8 cm ovarian mass on imaging during evaluation for acute abdomen. Serum AFP is 1200 ng/mL, β-hCG is 15 mIU/mL, and LDH is 890 U/L. A diagnosis of yolk sac tumor (endodermal sinus tumor) is suspected. Which investigation is most appropriate to confirm histopathological diagnosis and assess the presence of other germ cell components?

Explanation

## Histopathological Confirmation of Germ Cell Tumors **Key Point:** Once tumor markers confirm a germ cell tumor diagnosis, **definitive histopathological diagnosis requires surgical specimen examination**. In a young woman with a germ cell tumor, conservative surgery (unilateral oophorectomy) is performed, and the entire specimen is examined for histological type and presence of mixed components. ### Why Surgical Specimen Histopathology Is Gold Standard **High-Yield:** Germ cell tumors are often **mixed**, containing multiple histological components (yolk sac, choriocarcinoma, embryonal carcinoma, teratoma). A single biopsy may miss other components. The entire surgical specimen must be examined to: 1. Confirm the primary histological type 2. Identify all germ cell components present 3. Assess grade and stage 4. Guide chemotherapy regimen selection ### Histological Features of Yolk Sac Tumor | Feature | Finding | |---------|----------| | **Microcystic pattern** | Honeycomb-like spaces (Schiller-Duval bodies) | | **Schiller-Duval bodies** | Papillae with central blood vessel — pathognomonic | | **Hyaline globules** | PAS-positive, diastase-resistant (contain AFP) | | **Immunohistochemistry** | AFP+, SALL4+, cytokeratin+ | **Clinical Pearl:** Schiller-Duval bodies are the **hallmark of yolk sac tumor** and are virtually diagnostic when present. However, they are not always present in every field, so extensive sampling of the entire specimen is essential. ### Why Other Investigations Are Inadequate **Mnemonic: "FNAC is Too Small" — Fine-needle aspiration cytology cannot sample the entire tumor and may miss mixed components or diagnostic structures.** ```mermaid flowchart TD A[Ovarian mass + elevated AFP/β-hCG/LDH]:::outcome --> B[Diagnosis: Germ Cell Tumor suspected]:::outcome B --> C{Histological confirmation needed?}:::decision C -->|FNAC| D[Small sample, may miss components]:::urgent C -->|Core needle biopsy| E[Better sampling, but incomplete]:::outcome C -->|Surgical specimen| F[Entire tumor examined, all components identified]:::action F --> G[Definitive diagnosis + treatment planning]:::outcome ``` **Warning:** Do NOT rely on FNAC or core needle biopsy for germ cell tumors. These tumors are heterogeneous, and sampling error can lead to missed diagnosis of mixed components, which affects chemotherapy selection. [cite:Robbins 10e Ch 22]