Anatomical Pathology Interesting Case Conference

Microscopic Description:

Mixed germ cell tumor (teratoma 90%, yolk sac tumor 10%)

Secondary embryonic type neuroectodermal (ENT) tumor in association with teratoma

Tumor confined to testis/tunica albuginea/rete with no lymphovascular invasion

Immunohistochemistry:

  • AE1/AE3 positive
  • EMA, CDX2, AFP, S100, GFAP, synaptophysin, CD117 focally positive
  • PLAP, chromogranin, hCG negative

Mixed germ cell tumor (teratoma 90%, yolk sac tumor 10%) with secondary embryonic type neuroectodermal tumor

No direct invasion of tunica albuginea or rete

No lymphovascular invasion

Lung mass was diagnosed as a primary squamous cell carcinoma

pTNM: pT1 NX

Discussion:

Testicular germ cell tumor classification:

  • Germ cell tumors are divided into tumors derived from germ cell neoplasia in situ (GCNIS) and GCNIS-unrelated
    • GCNIS tumors are subdivided into seminomatous and nonseminomatous germ cell tumors
    • GCNIS-unrelated tumors include prepubertal-type teratoma, prepubertal yolk sac tumor, and mixed prepubertal germ cell tumors

Mixed germ cell tumor of testis (Teratoma and yolk sac tumor):

  • Around 1/3 of all testicular germ cell tumors are mixed, with two or more GCT types within a single mass
  • Prepubertal teratomas are usually benign and found in children
  • Postpubertal teratomas are usually malignant and usually seen in mixed germ cell tumors
    • A small fraction (3-6%) of germ cell tumors present with a somatic-type malignancy
    • Ex: squamous cell carcinoma, adenocarcinoma, immature neuroectodermal elements, or sarcoma
    • Embryonic-type neuroectodermal tumors (ENT) replaced primitive neuroectodermal tumor (PNET) to not misinterpret it as a Ewing sarcoma but more as a CNS tumor based on molecular profile (lacks EWSR1 rearrangement)
    • Teratoma component is seen in nearly 1/3 of all mixed germ cell tumors
  • Yolk sac tumor occurs in 40% of mixed germ cell tumors in adults
    • Accompanied with increased serum AFP, usually >100 ng/mL

Microscopic (histologic) description:

  • Mature cystic teratomas (dermoid cysts)
    • Only squamous epithelium, skin adnexal structures, and no immature elements
    • Benign epidermoid cysts contain only keratinizing squamous epithelium and no other elements
  • Mature teratoma: Heterogenous collection of differentiated cells or organoid structures embedded in a fibrous or myxoid stroma
    • Respiratory tract, gut, pancreas, thyroid, cartilage, squamous epithelium, skin adnexal structures
  • Immature teratomas have undifferentiated tissue seen in embryonic stages of development
  • Yolk sac tumors are the most morphologically variable of all GCTs
  • ENT tumor appears as immature neuroectodermal elements
  • Check for invasion into the tunica albuginea or tunica vaginalis membranes, or rete testis
References:

Cheng L, Zhang S, MacLennan GT, Poulos CK, Sung MT, Beck SD, Foster RS. Interphase fluorescence in situ hybridization analysis of chromosome 12p abnormalities is useful for distinguishing epidermoid cysts of the testis from pure mature teratoma. Clin Cancer Res. 2006 Oct 1;12(19):5668-72. doi: 10.1158/1078-0432.CCR-06-0976. PMID: 17020968

Al-Obaidy KI, Idrees MT. Testicular Tumors: A Contemporary Update on Morphologic, Immunohistochemical and Molecular Features. Adv Anat Pathol. 2021 Jul 1;28(4):258-275. doi: 10.1097/PAP.0000000000000302. PMID: 33871428.

Siegenthaler A, Niforatos S, Loon T, Brady A, Sandhu M, Kravtsov O, Akhtar K. Transformed Testicular Teratoma to Embryonic-Type Neuroectodermal Tumor With Metastasis to Mediastinum. J Investig Med High Impact Case Rep. 2023 Jan-Dec;11:23247096231218145. doi: 10.1177/23247096231218145. PMID: 38097381; PMCID: PMC10725136.

https://www.pathologyoutlines.com/topic/testisteratocarcinoma.html

https://www.uptodate.com/contents/clinical-manifestations-diagnosis-and-staging-of-testicular-germ-cell-tumors?search=testicular%20tumor&source=search_result&selectedTitle=1%7E109&usage_type=default&display_rank=1

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