Gonadoblastoma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2]
Overview
Historical Perspective
Gonadoblastoma was first discovered by Dr. Scully in 1953. The association between GBY gene (GonadoBlastoma on the Y chromosome) and gonadoblastoma was made in 1986. In 1995, Tsuchiya found that the GBY gene located near the centromere of Y chromosome and contains multiple genes including Testis-specific protein Y-encoded (TSPY) gene.
Classification
Gonadoblastoma may be classified according to pathological appearance into three sub-types including classical, dissecting, and burnt-out.
Pathophysiology
The exact pathogenesis of gonadoblastoma is not fully understood. Gonadal development starts at 5 weeks of gestation and continues according to sex chromosomes. Any defects in this complicated process leads to defective gonadal development and gonadal dysgenesis and subsequently, it may be converted to gonadoblastoma in 20% to 30% of the cases.
Causes
There are no established causes for gonadoblastoma. However, there are certain risk factors that predispose to increased risk of gonadoblastoma.
Differentiating Xyz from Other Diseases
Gonadoblastoma must be differentiated from other diseases that cause virilization, and primary amenorrhea and also must be differentiated pathologically from dysgerminoma, Sex-cord stromal tumors, and Sertoli-cell nodules.
Epidemiology and Demographics
The prevalence of gonadoblastoma depends on the chromosomal content, presence or absence of mosaicism, gonadal histology, and age of the patient and varies between 15,000 to 30,000 per 100,000 individuals worldwide. The incidence of gonadoblastoma varies according to the presence or absence of Y chromosomal content and age of the individual. Patients with Turner syndrome who have Y chromosomal content either completely or partially may develop gonadoblastoma with an incidence as high as 43,000 per 100,000 individuals worldwide. The incidence of gonadoblastoma among phenotypical females with XY gonadal abnormalities have been observed to be 40,000 per 100,000 individuals worldwide. Gonadoblastoma may be found at any age, but commonly presents before the age of 15 years. Since, it usually affects individuals with gonadal dysgenesis, there is no genotype-phenotype correlation. Phenotypically, it tends to affect female individuals to a greater extent.
Risk Factors
The most potent risk factor in the development of gonadoblastoma is gonadal dysgenesis. The risk also increases with age.
Screening
There is insufficient evidence to recommend routine screening for gonadoblastoma. However, patients with XY gonadal abnormalities should be followed using sonography starting at age 2, every six months, until the gonads are removed.
Natural History, Complications, and Prognosis
Gonadoblastoma per se is a benign tumor, however, it has the capacity to convert to dysgerminoma or other more malignant germ cell tumors and produce steroids with resultant virilization. Prognosis is generally excellent after removing the tumor.
Diagnosis
Diagnostic Study of Choice
There are no established criteria for the diagnosis of gonadoblastoma. It is often found during a workup for ambiguous genitalia in infancy or sexual developmental disorder in puberty. Chromosomal analysis plays the most beneficial role in the diagnosis of conditions associated with gonadoblastoma. However, sometimes the Y chromosome materials are present in molecular level and cannot be diagnosed karyotypically. In theses individuals, molecular analysis of chromosomes using polymerase chain reaction (PCR) and/or fluorescence in situ hybridization (FISH) may be helpful.
History and Symptoms
Patients with gonadoblastoma present either during infancy with ambiguous genitalia or later with sexual developmental complaints. The hallmark of gonadoblastoma is gonadal developmental disorders.
Physical Examination
Gonadoblastoma has no characteristic physical feature, however, any clue to the existence of an intersex disorder must raise the concern for diagnosing the coexisting gonadoblastoma.