Testis & paratestis
Germ cell tumors
Cystic trophoblastic tumor
Author: Vikas Mehta, M.D.
Editorial Board Member: Debra L. Zynger, M.D.
Last author update: 1 November 2017
Last staff update: 5 September 2023 (update in progress)
Copyright: 2017-2023, PathologyOutlines.com, Inc.
PubMed Search: Cystic trophoblastic tumor full text[sb]
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Mehta V. Cystic trophoblastic tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisctt.html. Accessed November 29th, 2023.
Definition / general
- Distinctive trophoblastic lesion secondary to either spontaneous or chemotherapy induced regression of choriocarcinoma
- Described predominantly in postchemotherapy retroperitoneal lymph node dissections of patients with testicular germ cell tumors
- Has also been described in both treated and untreated testes of patients with mixed germ cell tumors as well as in postchemotherapy primary central nervous system germ cell tumors
Essential features
- Cystic proliferation of trophoblast cells in postchemotherapy resections from patients with metastatic, nonseminomatous germ cell tumors of the testis
- Not aggressive with behavior believed to be similar to post-chemotherapy residual teratoma
Terminology
- Cystic trophoblastic tumor (CTT)
- Previously known as choriocarcinoma-like lesion (CCLL) with two subtypes: teratomatous CCLL and cystic atypical choriocarcinoma (Am J Surg Pathol 1988;12:531)
ICD coding
- ICD-10: C63.9 - malignant neoplasm of male genital organ, unspecified
Epidemiology
- Typically seen in young males aged 16 - 40
Sites
- Postchemotherapy retroperitoneal lymph nodes with mixed germ cell tumors
- Treated or untreated testes with mixed germ cell tumors
- Postchemotherapy primary central nervous system germ cell tumor
Etiology
- May arise from regressing choriocarcinoma as the more aggressive cells are eliminated by chemotherapy or spontaneous regression, leading to the persistence of a slow growing, less aggressive component of intermediate type trophoblasts that develops into cystic trophoblastic tumor (Am J Surg Pathol 2017;41:788)
- Cystic trophoblastic tumor may also represent an intermediate stage in the maturation of choriocarcinoma to teratoma (Am J Surg Pathol 2004;28:1212)
Clinical features
- Most commonly seen in patients with testicular germ cell tumors after cisplatin based chemotherapy
Diagnosis
- Histologic examination of involved tissue
Laboratory
- Normal to mildly elevated levels of subunit of human chorionic gonadotropin (β hCG)
Radiology description
- Enlarged retroperitoneal lymph nodes
Case reports
- 12 year old boy with cystic trophoblastic tumor arising in a postchemotherapy primary central nervous system germ cell tumor (Am J Clin Pathol 2016;146:S104)
- 31 year old man with metastatic cystic trophoblastic tumor without prior chemotherapy (Urol Case Rep 2017;13:154)
Treatment
- Requires no further treatment, however these patients should be carefully monitored on follow up
Gross description
- No grossly distinguishable features
Microscopic (histologic) description
- Solid foci or small clusters of modestly pleomorphic trophoblastic cells and variably sized, degenerative appearing cysts, typically measuring less than 3 mm with circumscribed borders
- Cysts are lined by trophoblast cells with abundant, eosinophilic cytoplasm that vary from a single cell layer to several in thickness, forming intracystic papillary tufts or cribriform arrangements
- Most of the lining cells are mononucleated and many have a smudged chromatin pattern, although occasional multinucleated cells occur, sometimes with cytoplasmic lacunae
- Many of the lining cells have a squamoid appearance, although no extracellular keratin production is apparent
- Mitotic activity is inconspicuous, with only rare mitotic figures identified
Microscopic (histologic) images
Contributed by Vikas Mehta, M.D.
Large cyst in CTT
Intermediate type trophoblasts
Small cyst formation
β hCG
Differential diagnosis
- Epithelioid trophoblastic tumor (ETT)
- Placental site trophoblastic tumor (PSTT)
- Regressing choriocarcinoma
- Somatic malignancy, such as squamous cell carcinoma, when the tumor is more cellular and contains solid foci
Additional references
Board review style question #1
Choriocarcinoma is distinguished from cystic trophoblastic tumor by all of the following features except:
- Biphasic pattern of admixed cytotrophoblast and syncytiotrophoblast cells
- Infiltrative growth pattern
- Normal to mildly elevated serum levels of β hCG
- Variable SALL4 expression in mononuclear cells
Board review style answer #1
C. Normal to mildly elevated serum levels of β hCG
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Board review style question #2
Which of the following statements is true for cystic trophoblastic tumors (CTTs)?
- CTTs after chemotherapy show a high frequency of progressive disease and warrant additional chemotherapy
- CTTs are identified exclusively in the setting of postchemotherapy retroperitoneal lymph node dissections of patients with testicular germ cell tumors
- CTTs lack keratohyaline granules and central keratin, often have intracytoplasmic lacunae
- CTTs show goblet cells, ciliated cells and other specialized epithelial types
Board review style answer #2
C. CTTs lack keratohyaline granules and central keratin, often have intracytoplasmic lacunae
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