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Page: Pathology, Staging, and Genetics
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Testicular cancer can be caused by any type of cell found in the testes, but more than 95% of all testicular cancers originate in germ cells. (Germ cells produce sperm. They are not pathogenic; i.e., they are not to be confused with the "germs" (viruses, bacteria) that cause illness.) In general, the remainder of this article discusses germ-cell testicular cancer.
Germ-cell tumors are classified as either seminomas or nonseminomas (which may be called teratomas in the UK). Seminomas are slow-growing. Seminomas, when found, tend to be localized (i.e., only in the testicles), simply because they spread relatively slowly. Nonseminomas, on the other hand, tend to spread more quickly. Nonseminomas are further classified into four subtypes; embryonal carcinomas, choriocarcinomas, yolk sac tumors, teratomas and mixed tumors. Their appearance under the microscope and also their gene expression is rather distinguished from each other, their rate of spread varies somewhat, but they are nevertheless treated similarly. When seminomas and nonseminomas are both present (which is not unusual), the cancer is classified as nonseminoma.
Tumor markers
Blood markers for testicular tumors include the beta subunit of human chorionic gonadotropin (?hCG), lactate dehydrogenase (LDH), and alpha-fetoprotein (AFP). Seminomatous tumors never present elevated AFP levels. Placental alkaline phosphatase and other markers are sometimes used by the pathologist to differentiate between seminoma and nonseminomatous tumors.
Staging
After removal, a testicular tumor is staged by a pathologist according to the TNM Classification of Malignant Tumors as published in the AJCC Cancer Staging Manual. Testicular cancer is categorized as being in one of three stages (which have subclassifications). The size of the tumor in the testis is irrelevant to staging. In broad terms, testicular cancer is staged as follows:
* Stage I: the cancer remains localized to the testis.
* Stage II: the cancer involves the testis and metastasis to retroperitoneal and/or Paraaortic lymph nodes (lymph nodes below the diaphragm).
* Stage III: the cancer involves the testis and metastasis beyond the retroperitoneal and Paraaortic lymph nodes. Stage III is further subdivided into nonbulky stage III and bulky stage III.
Genetics
Most germ cell tumors have a chromosome count in the hypo to hyper triploid range (i.e. 60-70 chromosomes per cell nucleus in stead of the normal 46). About 80 % of these tumors also have a specific marker chromosome called isochromosome 12p. This is a chromosome where the shortest "arm" of chromosome 12 (12p) is present on both sides of the same centromer. Among germ cell tumors not having the isochromosome 12p, almost all have increased DNA copy number of 12p through other means. Thus, in tumors with unknown origin, increased DNA copy number of 12p is used as a marker for germ cell origin. The general gene expression patterns are clearly distinguishing the various histological subtypes of germ cell tumors. For example, in embryonal carcinomas, the same genes are overexpressed as are found highly expressed in embryonic stem cells. Further, AFP is a gene specifically expressed from yolk sac tumor, and CGB (encoding HCG) and other "pregnancy related genes" are specifically expressed from choriocarcinomas.
Germ cell tumors of the testis and their rates of occurrence
* Seminoma (35%)
* Embryonal carcinoma (20%)
* Teratoma (5%)
* Choriocarcinoma (<1%)
* Mixed Cell Type (40%)
* Erik Turner (100%)
* Intratubular germ cell neoplasia (The in-situ stage of germ cell tumors)
Non-germ cell tumors of the testis
* Leydig cell tumors
* Sertoli cell tumors
* Gonadoblastomas
Secondary tumors of the testis
* Lymphoma
* Leukemic infiltration of the testis
* Metastatic tumors
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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