Testis & paratestis

Germ cell tumors

Epithelioid trophoblastic tumor



Last staff update: 19 November 2024 (update in progress)

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PubMed Search: Epithelioid trophoblastic tumor

Priyanka Gupta, M.B.B.S., D.N.B.
Vikas Mehta, M.D.
Page views in 2024 to date: 155
Cite this page: Gupta P, Mehta V. Epithelioid trophoblastic tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisepithelioidtrophoblastictumor.html. Accessed December 4th, 2024.
Definition / general
Essential features
  • Epithelioid trophoblastic tumor (ETT) is an unusual trophoblastic tumor, distinct from choriocarcinoma and placental site trophoblastic tumor (PSTT) with morphologic features similar to a carcinoma
  • ETT has a squamoid appearance, with mostly mononucleated trophoblastic cells and a variable amount of fibrinoid material surrounding the tumor clusters and vessels
  • Both morphologic and immunohistochemical studies show that ETT is mainly composed of chorionic type intermediate trophoblastic cells
Terminology
  • Atypical choriocarcinoma
ICD coding
  • ICD-O: 9105/3 - trophoblastic tumor, epithelioid
  • ICD-11: 2C80.Y & XH8FW3 - other specified malignant neoplasms of testis & trophoblastic tumor, epithelioid
Epidemiology
Sites
Pathophysiology
  • Pathogenesis is not clear but it has been suggested that the tumor arises within a mixed germ cell tumor after reprogramming in the differentiation of the neoplastic cytotrophoblasts to produce ETT (Lancet Oncol 2007;8:642)
  • Chemotherapy may contribute to the differentiation of choriocarcinoma into ETT, which is more refractory to chemotherapy owing to its low proliferation activity; consequently, the ETT cells survive after the destruction of choriocarcinoma (Lancet Oncol 2007;8:642, Pathology 2018;50:88)
Etiology
  • Seems to develop from the neoplastic transformation of cytotrophoblastic cells that assume a differentiation toward the chorionic type intermediate trophoblastic cells that are normally found in chorion laeve (fetal membrane)
Clinical features
Diagnosis
  • Based on characteristic morphology and immunoprofile
Laboratory
  • May be associated with mild elevation of beta human chorionic gonadotrophin (βhCG)
Radiology description
  • No characteristic features
Prognostic factors
Case reports
Microscopic (histologic) description
  • Several growth patterns may be present including cohesive nests of squamoid cells with abundant pink cytoplasm and lacking associated hemorrhage
  • Tumor cells have single pleomorphic and hyperchromatic nuclei with prominent nucleoli and occasional multinucleation along with well defined cytoplasmic membranes without discernible intercellular bridges
  • Intracytoplasmic vacuoles containing fibrinoid cellular debris, sometimes with pyknotic nuclear fragments can be identified
  • Extracellular hyaline material and lymphocytes at the periphery with Infiltrating tumor nests and single squamoid cells can also be recognized
  • Mitotic count ranges from few to several in different fields
  • Occasional central cystic degeneration containing fibrinoid material is noted
  • Most striking histologic feature is an absent biphasic pattern of cytotrophoblasts and syncytiotrophoblasts
Microscopic (histologic) images

Contributed by Debra L. Zynger, M.D.
Tumor metastatic to shoulder

Tumor metastatic to shoulder

Mononucleate cells

Mononucleate cells

Prominent cell borders

Prominent cell borders

Positive stains
Sample pathology report
  • Retroperitoneal lymph node, lymph node dissection:
    • Metastatic testicular germ cell tumor, teratoma (60%) and epithelioid trophoblastic tumor (40%) (see comment)
    • Comment: The epithelioid trophoblastic tumor expresses AE1 / AE3, inhibin, p63 and GATA3.
Differential diagnosis
  • Choriocarcinoma:
    • Very high serum βhCG
    • Shows a biphasic pattern of syncytiotrophoblastic and mononucleated trophoblast cells and significant fresh hemorrhage, often with extensive necrosis
    • Higher mitotic activity
    • βhCG and HPL expression are diffuse rather than focal
  • Regressing choriocarcinoma:
    • Large mononucleated trophoblast cells with pale to eosinophilic cytoplasm
    • Absent biphasic pattern of cytotrophoblasts and syncytiotrophoblasts with necrosis and fresh hemorrhage along with hyalinized fibrous background and numerous hemosiderin laden macrophages
    • Few mitotic figures
    • Prominent Leydig cell hyperplasia in the surrounding testis
  • Placental site trophoblastic tumor:
    • Sheets of discohesive cells with focal hemorrhage
    • More infiltrative growth instead of nodules and nests
    • Larger cells with more pleomorphic nuclei
    • p63 negative
  • Squamous cell carcinoma, as a component of teratoma with somatic malignancy:
    • Also has concurrent testicular germ cell tumor with other components or a history of testicular germ cell tumor with subsequent metastasis
    • Keratin pearls or more overt, classic squamous appearance
    • Inhibin, βhCG, HPL negative
  • Squamous cell carcinoma, nontesticular in origin:
    • Correlation with history of other malignancies and current imaging required
    • Keratin pearls or more overt, classic squamous appearance
    • Inhibin, βhCG, HPL negative
Board review style question #1

A patient with a history of testicular germ cell tumor treated with chemotherapy now has an enlarged cervical lymph node that is diffusely involved by the tumor (shown above). There is only a minor elevation of serum βhCG. The tumor is formed by large, solid nodules of cells with a squamoid appearance. The cells are homogeneous and intermediate to large in size, consistent with mononucleated trophoblastic cells. The tumor cells express AE1 / AE3, patchy inhibin and p63 and only focal βhCG. What is the best diagnosis?

  1. Choriocarcinoma
  2. Cystic trophoblastic tumor
  3. Epithelioid trophoblastic tumor
  4. Myoid gonadal trophoblastic tumor
Board review style answer #1
C. Epithelioid trophoblastic tumor (ETT). Essential diagnostic criteria of ETT (WHO 5th edition) include squamoid appearing, mostly mononucleated trophoblastic cells with a variable amount of fibrinoid material surrounding the tumor clusters and vessels. Desirable diagnostic criteria of ETT (WHO 5th edition) include positive staining for p63 and Ki67 index > 10%. Answer A is incorrect because choriocarcinoma has a biphasic pattern of syncytiotrophoblastic and mononucleated trophoblast cells and patients with a substantial burden of choriocarcinoma have high serum βhCG. Answer B is incorrect because cystic trophoblastic tumors have a degenerative appearance with cysts lined by squamoid appearing cells with smudged, irregular nuclei, abundant eosinophilic cytoplasm with intracytoplasmic lacunae and associated fibrinoid material. Answer D is incorrect because myoid gonadal trophoblastic tumor is a pure spindle cell tumor lacking sex cord differentiation and is positive for both actin and S100.

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Reference: Epithelioid trophoblastic tumor
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