Mixed Germ Cell Tumors



Mixed Germ Cell Tumors


Steven S. Shen, MD, PhD

Jae Y. Ro, MD, PhD










Large MGCT with a variegated cut surface replaces the testicular parenchyma. The tumor is predominantly teratoma image; other areas are solid, hemorrhagic, and necrotic EC and YST components image.






A MGCT composed of variable germ cell tumor components includes mature teratoma (including cartilage, bone, and squamous nest image), immature teratoma image, EC image, and YST image.


TERMINOLOGY


Abbreviations



  • Mixed germ cell tumor (MGCT), mixed nonseminomatous germ cell tumor (MNSGCT)


Synonyms



  • Mixed nonseminomatous germ cell tumor


Definitions



  • Germ cell tumor composed of > 1 histologic type of germ cell tumor, including seminoma


CLINICAL ISSUES


Epidemiology



  • Incidence



    • 2nd most common germ cell tumor after seminoma


    • Accounts for 30-40% of all testicular germ cell tumors


  • Age



    • Range: 20-40 years (10 years younger than seminoma)


    • Rarely seen in prepubertal children and older adults (> 50 years)


Presentation



  • Testicular mass or swelling ± pain


Treatment



  • Similar to pure nonseminomatous germ cell tumor and depends on clinical stage


  • Radical inguinal orchiectomy ± retroperitoneal lymph node dissection or adjuvant therapy


Prognosis



  • Depends on clinical stage, proportion of embryonal carcinoma (unfavorable) and mature teratoma (favorable) component, and lymphovascular invasion


  • Cure rate > 95% for stage I and stage II disease


  • Cure rate approximately 70-85% for stage III disease


IMAGE FINDINGS


Radiographic Findings



  • Heterogeneous testicular mass on ultrasound examination


  • May be accompanied by retroperitoneal lymph node enlargement


MACROSCOPIC FEATURES


General Features



  • Variegated cystic and solid mass with hemorrhage and necrosis


  • Seminomatous germ cell component with solid white and gray areas


  • Nonseminomatous component with granular and firm areas with hemorrhage, necrosis, and cystic areas


  • Teratoma with bone, cartilage, and skin elements


Sections to Be Submitted



  • Multiple sections of different areas of tumor and at least 1 section per cm tumor


  • Should include necrotic and hemorrhagic areas


Size



  • Variable, often large bulky mass


MICROSCOPIC PATHOLOGY


Histologic Features



  • Variable combination and percentage of all germ cell tumor components


  • Embryonal carcinoma (EC) and teratoma (T) are most common (26%)


  • Other combinations include



    • EC and seminoma (S) (16%)


    • EC, yolk sac tumor (YST), and T (11%)



    • EC, T, and choriocarcinoma (CC) (7%)


    • EC, T, and S (6%)


    • T and S (6%)


    • EC and YST (4%)


    • EC and CC (4%)


    • Other combinations may occur (16%)


  • Areas of necrosis and hemorrhage are common


  • Rare variants include polyembryoma and diffuse embryoma



    • Polyembryoma is composed of entirely or predominantly embryoid bodies with embryonic disc, yolk sac, and surrounded by myxoid stroma


    • Diffuse embryoma is characterized by intimately admixture of EC and YST with YST wrapping around EC component


Cytologic Features



  • Reflects histologic composition of each component


Predominant Pattern/Injury Type



  • Neoplastic


Predominant Cell/Compartment Type



  • > 1 type of germ cell tumor component


ANCILLARY TESTS


Immunohistochemistry



  • Immunoprofile reflects histologic component of different germ cell tumors


  • 1st-line germ cell markers: Oct3/4, PLAP, Podoplanin(D2-40), CD30(BerH2), α-fetoprotein, HCG, cytokeratin


  • Other germ cell markers: CD117, glypican-3, SALL4, NANOG


DIFFERENTIAL DIAGNOSIS


Pure Germ Cell Tumor



  • Such as embryonal carcinoma, yolk sac tumor, or teratoma


  • Multiple sections are required to demonstrate different germ cell tumor components


Metastatic Carcinoma



  • Old age, history, and bilaterality


  • Interstitial pattern is frequently seen in metastatic carcinoma


  • Positive for EMA/MUC1; negative for germ cell tumor markers


DIAGNOSTIC CHECKLIST


Pathologic Interpretation Pearls



  • Mixture of different histologic components of germ cell neoplasm


REPORTING CONSIDERATIONS


Key Elements to Report



  • Specific histologic types and percentage of each component


  • Lymphovascular invasion


  • Involvement of rete testis, epididymis, spermatic cord, and tunica


  • Pathology of uninvolved testicular parenchyma



SELECTED REFERENCES

1. Berney DM et al: Malignant germ cell tumours in the elderly: a histopathological review of 50 cases in men aged 60 years or over. Mod Pathol. 21(1):54-9, 2008

2. Mosharafa AA et al: Histology in mixed germ cell tumors. Is there a favorite pairing? J Urol. 171(4):1471-3, 2004

3. Sesterhenn IA et al: Pathology of germ cell tumors of the testis. Cancer Control. 11(6):374-87, 2004

4. Ayala AG et al: Testicular tumors: clinically relevant histological findings. Semin Urol Oncol. 16(2):72-81, 1998






Image Gallery




Gross and Microscopic Features






(Left) MGCT usually shows an irregular mass with variegated cut surface. Creamy gray lobulated areas suggest seminoma image, mucoid areas suggest teratoma image, and hemorrhagic brown areas suggest EC image. Gross appearances are not absolutely specific for histologic subtype. (Right) MGCT with typical variegated cut surface is shown. The cystic mucoid areas represent mature teratoma image, the tan fleshy area represents seminoma image, and hemorrhagic and necrotic areas represent EC image.

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Mixed Germ Cell Tumors
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