Yolk Sac Tumor



Yolk Sac Tumor


Steven S. Shen, MD, PhD

Mahul B. Amin, MD

Jae Y. Ro, MD, PhD





Key Facts


Terminology



  • Germ cell tumor characterized by variety of growth patterns that recapitulate yolk sac, allantois, and extraembryonic mesenchyme


Clinical Issues



  • Most common germ cell tumor of infants and young children


  • No association with cryptorchidism


  • Pure form rare in adults: Usually present as component of mixed germ cell tumors


Microscopic Pathology



  • YST has multiple growth patterns with 1 dominant pattern or more frequently mixed patterns



    • Reticular or microcystic pattern most frequent (80%)


    • Other common patterns include endodermal sinus, solid, papillary, and glandular


  • Relatively uniform cells with clear or vacuolated to lightly eosinophilic cytoplasm


  • Bland cuboidal, columnar to flattened, or spindle cells


  • Presence of small, spherical, intracellular or extracellular hyaline globules


  • Prominent basement membrane deposition


Ancillary Tests



  • Positive for cytokeratin, AFP, PLAP (variable), SALL4, glypican-3


  • Negative for CD30(BerH2), Podoplanin(D2-40), Oct3/4, hCG, inhibin-α



    • Podoplanin(D2-40) and Oct3/4 are positive in seminoma and embryonal carcinoma







H&E shows microcystic and reticular YST patterns in which tumor cells contain vacuolated cytoplasm, intercellular eosinophilic globules image, & extracellular pink basement membrane-like material image.






This image shows a Schiller-Duval body in YST, which is characterized by a central vessel surrounded by a layer of tumor cells, a hollow space, and another layer of similar or more flattened cells.


TERMINOLOGY


Abbreviations



  • Yolk sac tumor (YST)


Synonyms



  • Endodermal sinus tumor (EST)


Definitions



  • Germ cell tumor characterized by variety of growth patterns that recapitulate yolk sac, allantois, and extraembryonic mesenchyme


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Pure YST is most common testicular tumor of infants and young children



      • Accounts for 75% of all childhood testicular neoplasms


      • No association with cryptorchidism or other germ cell tumor components


    • Pure YST is extremely rare in adult testes



      • At extragonadal sites, especially mediastinum, pure YST may be seen


    • YST is frequent component of mixed germ cell tumors (in ~ 40%) in adults


  • Age



    • Mean age: 16-18 months for pure YST


    • Mean age: 25-35 years for adult YST



      • 10 years younger than patients with seminoma


Presentation



  • Nonsymptomatic, rapid testicular enlargement


  • Approximately 90% of patients with childhood YST have clinical stage I disease


  • Presence of YST in adult patients with mixed germ cell tumor is frequently associated with lower stage presentation


Laboratory Tests



  • More than 95% patients have elevated serum α-fetoprotein (AFP)


  • Test for serum AFP is valuable tool in diagnosis and monitoring effectiveness of therapy


Treatment



  • For infants and children with pure YST



    • Radical inguinal orchiectomy for stage I tumor with close follow-up protocol (surveillance)


    • Cisplatin-based therapy for relapse on surveillance, advanced stage disease, or metastasis


  • For adult YST (usually mixed with other germ cell tumor)



    • Similar to other nonseminomatous germ cell tumor based on clinical stage


    • Radical inguinal orchiectomy ± retroperitoneal lymph node dissection


    • Cisplatin-based chemotherapy for metastatic disease


Prognosis



  • Prognosis associated with clinical stage, lymphovascular invasion, degree of serum AFP elevation


  • Children have better prognosis than adults


IMAGE FINDINGS


General Features



  • Ultrasonography may detect scrotal mass


MACROSCOPIC FEATURES


General Features



  • Nonencapsulated, gray-white, soft or firm, homogeneous mass


  • Typical myxoid or gelatinous cut surface


  • Hemorrhage and necrosis may be present


  • Tumors in adults are typically more heterogeneous



Size



  • Range: 2-6 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • YST frequently has multiple growth patterns with 1 dominant pattern



    • Microcystic or reticular pattern most frequent (80%)



      • Anastomosing thin cords forming round or irregular spaces or tubules of variable size


      • Characteristic intracellular vacuoles and merging of cells create sieve-like appearance


      • Nuclei are irregularly shaped (round, columnar, stellate, triangular) and are often pushed to edge of cells


    • Endodermal sinus pattern



      • Composed of numerous Schiller-Duval bodies (resembling fetal glomeruli) with central fibrovascular core


      • Fibrovascular core is lined by cuboidal to columnar tumor cells, which are surrounded by cystic spaces and more flattened layer of tumor cells


      • Labyrinthine spaces or perivascular arrangement of tumor cells are common


    • Solid pattern



      • Solid sheets of polygonal tumor cells with pale eosinophilic or clear cytoplasm, which lack fibrovascular septae, lymphocytes, or granulomas


      • May be confused with seminoma, embryonal carcinoma, and monophasic areas of choriocarcinoma


      • Tumor cells with random pleomorphism; slightly greater atypia than seminoma but less than embryonal carcinoma


    • Papillary and tubulopapillary



      • Papillae ± central fibrovascular cores


      • Tumor cells are often cuboidal and low columnar with “hobnail” appearance


    • Polyvesicular vitelline pattern



      • Large constricted vesicles lined by flattened to cuboidal cells


      • Often associated with abundant myxoid or loosely fibrous stroma


    • Glandular-alveolar pattern



      • Simple round to complex branching glands with intervening myxoid stroma


    • Parietal pattern



      • Epithelial cells surrounded by pink bands of basement membrane material


    • Enteric or endometrioid pattern



      • Glandular pattern with columnar cells, cytoplasmic clearing, subnuclear vacuoles, and smooth luminal surface


    • Hepatoid pattern



      • Sheets of tumor cells with abundant eosinophilic cytoplasm and eosinophilic globules


    • Spindled cell or sarcomatoid pattern



      • Composed of spindle (or sarcomatoid) cells with myxoid stroma


    • Myxomatous pattern



      • Epithelioid to spindle cells dispersed in paucicellular light blue myxoid stroma


      • Frequently under-recognized due to innocuous appearance


    • Macrocystic pattern



      • Large cystic spaces due to coalescence of microcysts lined by flattened tumor cells


    • Mixed pattern



      • Mixture of any of above growth patterns


  • Intra- and extracellular PAS-positive hyaline globules



    • More commonly seen in microcystic and reticular, solid, and hepatoid patterns


Cytologic Features

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Yolk Sac Tumor

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