Testicular germ cell neoplasia in situ

INTRODUCTION — Testicular germ cell neoplasia in situ (GCNIS; formerly known as intratubular germ cell neoplasia of the unclassified type [1]) is generally considered to be a precursor of most testicular germ cell tumors (GCTs), except for spermatocytic tumors (also known as spermatocytic seminomas) in adult males as well as yolk sac tumors and mature teratomas in infants. However, this is not an epithelial lesion, and thus, the term "germ cell carcinoma in situ" should not be used. GCNIS is noninvasive because the neoplastic cells are confined within the seminiferous tubules.

GCNIS is discussed here. Other related topics include:

●(See "Epidemiology and risk factors for testicular cancer".)

●(See "Clinical manifestations, diagnosis, and staging of testicular germ cell tumors".)

PATHOGENESIS — GCNIS can be found in testicular tissue adjacent to GCTs in more than 90 percent of adult GCTs [2,3]; it can also be found in all groups of males at high risk for testicular cancer, including males with cryptorchid testes [4-6], prior testicular cancer development [7-9], and in individuals with abnormal sexual differentiation [4,10]. However, GCNIS is not found in patients with childhood forms of testicular GCT [11,12], and there is no clear association between GCNIS and testicular GCTs in prepubertal males.

The prevalence of GCNIS in these populations mirrors that of GCTs; this reproducible observation has contributed significantly to the theory that GCNIS is the precursor of GCTs [13,14]. These observations also suggest there is a field defect in which genetic or developmental events that produce gonadal dysfunction confer predisposition to malignancy in both gonads [15].

GCNIS cells are derived from primordial germ cells and are believed to be present at birth [16,17]; as an example, testicular GCNIS has been found in infants as young as one month old [16,18]. Although the exact developmental stage at which GCNIS arises is controversial, the 8th through 12th weeks of gestation are the focus of much attention. Two proteins, the c-kit receptor (KIT) and placental-like alkaline phosphatase (PLAP), are overexpressed by GCNIS cells; these and other markers are expressed by fetal germ cells only between the 8th and 12th week of development [19-21]. Furthermore, prolonged expression of c-kit has been found in the fetal testes of intersex individuals who are at high risk of developing early testis tumors [22]. (See 'Androgen insensitivity syndromes and mixed gonadal dysgenesis' below.)

The high incidence of testis cancer in males with cryptorchidism and other congenital errors of gonadal development points to intrauterine factors as playing an important role in the transformation of germ cells to GCNIS. During this period, which may be a crucial step in germ cell differentiation, either genetic factors (eg, gonadal dysgenesis) or environmental influences (eg, the estrogenic milieu) may lead germ cells to acquire malignant potential [18].

The altered hormonal environment during puberty may cause GCNIS cells to begin to replicate [16]. Initially, GCNIS spreads longitudinally in a noninvasive fashion along the seminiferous tubules. Upon reaching the rete testis, GCNIS cells spread to other tubules.

At some point following puberty, GCNIS becomes "invasive" (penetrating the basement membrane); however, invasion of the basement membrane is not synonymous with either seminomatous or nonseminomatous GCTs. The specific factors that lead to initiation and promotion of invasiveness have not been elucidated.

The GCNIS cell appears to be the precursor of all of the different phenotypic varieties of testicular GCTs, except spermatocytic tumors (also known as spermatocytic seminomas) in older adult males as well as yolk sac tumors and mature teratomas in young children [14,16,23]. Morphologically, GCNIS cells resemble seminomas more closely than nonseminomatous GCT. While it was originally thought that the GCNIS cell progressively differentiated into seminoma, and then into a nonseminomatous GCT, most now believe that GCNIS can progress along two different pathways, either from seminoma to nonseminomatous GCT [24], or from GCNIS into a nonseminomatous GCT directly [23,25]. This may be a result of the gradual loss of stem cell potential of the GCNIS cell with increasing age [18]. The infrequently termed "intratubular seminoma" (characterized by a GCNIS appearance without interspersed Sertoli cells) may not usefully be discriminated from GCNIS and should not be included in classifications of in situ disease, as both entities may be associated with either category of GCT [26].

PREVALENCE AND RISK FACTORS — The prevalence of GCNIS varies significantly between the general population and different subpopulations that are at increased risk for testis cancer. (See "Epidemiology and risk factors for testicular cancer", section on 'Risk factors'.)

Identified risk factors for GCNIS include:

●Contralateral testicular germ cell tumor (GCT)

●Extragonadal GCT

●Cryptorchid testis (regardless of orchidopexy) or the normal contralateral testis

●Infertile males

●Dysgenetic gonads

General population — The incidence of GCNIS in the general population is between 0.4 and 0.8 percent, which closely mirrors the incidence of testicular GCTs [27,28]. The incidence of GCNIS is illustrated by the following:

●A pathologic study involving 1388 otherwise-healthy German males who died unexpectedly and underwent bilateral testicular biopsy at autopsy yielded a GCNIS rate of 0.4 percent, consistent with the lifetime risk of GCT in Germany [13].

●Another study analyzed the testes of 399 Danish males who died unexpectedly between ages 18 and 50 [29]. There were no cases of GCNIS, although three had been previously treated for testicular tumor or GCNIS. Thus, the overall prevalence of testicular GCNIS was 0.8 percent, comparable to the lifetime risk of testicular cancer in the Danish male population.

Contralateral germ cell tumor — Males with testicular GCT are at risk of having GCNIS in the contralateral testis. In two large series from Denmark and Germany, approximately 5 percent of males with unilateral testicular GCT who underwent contralateral testis biopsy had GCNIS [7,8]. Systematic studies to evaluate the incidence of GCNIS in the contralateral testicle have not been performed in the United States.

The estimated incidence of bilateral testis cancer in American males who have unilateral testicular cancer is approximately 1 to 2 percent [30]. The prevalence of GCNIS in the contralateral testis of males with unilateral testis cancer substantially exceeds the lifetime risk of contralateral testis cancer, hence GCNIS may be necessary but, in itself, insufficient for contralateral testis cancer development. (See "Epidemiology and risk factors for testicular cancer", section on 'Germ cell neoplasia in situ'.)

Cryptorchidism — Cryptorchidism (undescended testis) refers to a testis that is not within the scrotum and cannot be manipulated manually to be within the scrotum by the age of one year. A history of cryptorchidism is the best established risk factor for GCNIS and invasive testicular cancer. (See "Undescended testes (cryptorchidism) in children: Clinical features and evaluation" and "Undescended testes (cryptorchidism) in children: Management".)

The prevalence of GCNIS in cryptorchid testes is age-dependent and is approximately 5 percent [28]. The diagnosis of GCNIS is usually established in postpubertal testes; it is difficult to establish in prepubertal testes because GCNIS cells resemble normal infantile gonocytes. (See 'Diagnosis' below.)

A history of cryptorchidism increases the risk of testicular cancer; it is highest in those with an intraabdominal undescended testicle. Early surgical correction may reduce the incidence of testicular cancer. Twenty-five percent of such GCT cases occur in the contralateral, normally descended testicle. (See "Epidemiology and risk factors for testicular cancer", section on 'Cryptorchidism'.)

It is unclear whether all cases of GCNIS in an undescended testicle progress to cancer. In one Swiss study, placental-like alkaline phosphatase (PLAP)-positive germ cells morphologically identical to adult GCNIS cells were found in 5 percent of prepubertal males with cryptorchidism undergoing orchidopexy [31]. After two decades of follow-up, none of these males developed testicular cancer, suggesting that GCNIS does not inevitably progress at least during this time period.

Because of the possible bleeding and other complications, a biopsy of the contralateral normal testicle at the time of orchidopexy is not recommended. Instead, most testis cancer experts and pediatric urologists advocate patient education and self-examination to monitor the risk of malignancy in the undescended testis.

Infertility — Testicular GCNIS is commonly associated with abnormalities in spermatogenesis and Leydig cell dysfunction [32], and males with impaired fertility are more likely to develop testicular cancer than other males with normal fertility [33,34]. In one series of 32,442 males undergoing semen analysis, 89 cases of testicular cancer were diagnosed; the standardized incidence ratio was 1.6 (95 percent confidence interval, 1.3 to 1.9) compared with the expected number of testicular cancers in the Danish male population [33]. (See "Epidemiology and risk factors for testicular cancer".)

Although systematic screening has not been performed, the incidence of GCNIS in males undergoing fertility evaluation has been approximately 1 percent or less [35-37].

Extragonadal germ cell tumor — Up to 50 percent of males with extragonadal GCTs have GCNIS in one or both testes [38]. These findings suggest that the some extragonadal GCTs and testicular GCTs may have a common cell origin, or there may be a common stimulus for malignant transformation of primordial germ cells in both locations. However, it is known that extragonadal GCTs particularly mediastinal nonseminomatous GCTs usually have poorer prognosis than those of the testis. (See "Extragonadal germ cell tumors involving the mediastinum and retroperitoneum".)

Androgen insensitivity syndromes and mixed gonadal dysgenesis — Individuals with androgen insensitivity syndrome (individuals with 46XY chromosomes and mutations of the androgen receptors) or mixed gonadal dysgenesis are at risk for GCNIS as well as germinal and nongerminal neoplasms in cryptorchid gonads [39-42]. Approximately 5 to 10 percent of affected patients may harbor GCNIS [43,44]. (See "Pathogenesis and clinical features of disorders of androgen action" and "Diagnosis and treatment of disorders of the androgen receptor".)

DIAGNOSIS — The diagnosis of GCNIS requires the finding of neoplastic germ cells in a tissue specimen, either a testicular biopsy or orchiectomy specimens [45]. The testis harboring GCNIS is usually palpably normal. Radiographic findings is not specific for GCNIS and cannot be diagnostic, although it may suggest the need for biopsy. Serum markers such as alpha fetoprotein and the beta subunit of human chorionic gonadotropin are not elevated unless GCNIS is accompanied by an invasive neoplasm.

Indications for biopsy — Testicular biopsy is rarely performed for detection of GCNIS. It may only be considered for males at high risk for a testicular germ cell tumor (GCT) based upon known risk factors, such as gonadal dysgenesis. More commonly, GCNIS may be identified as an incidental finding on testicular needle core biopsy performed for infertility evaluation.

However, the role of testicular biopsy in males at high risk who present with a unilateral testicular GCT remains controversial, since biopsy and subsequent treatment of the contralateral testis is associated with a significant risk of hypogonadism.

●In some European countries, contralateral testicular biopsy is routinely offered at the time of primary orchiectomy because of a high incidence of GCNIS in the contralateral testes of males with a unilateral testicular GCT (5 to 6 percent) [7]. The rationale for this biopsy strategy is based upon the potential avoidance of more morbid therapy for a more advanced cancer should a contralateral testicular GCT arise, rather than an improvement in overall survival [46].

●By contrast, a more conservative approach is standard in North America since the risk of development of contralateral testicular cancer is on the order of 1 to 2 percent. Thus, it is unclear whether patients with GCNIS require treatment, and the impact of such treatment on survival and quality of life is not well characterized.

Testicular biopsy — An appropriate biopsy should be at least 3 by 3 mm in size and should contain at least 40 tubules on histologic cross-section in order to be representative of the entire testis [14]. With an appropriate biopsy, the risk of a false negative result and the development of subsequent cancer have been reported to be less than 0.5 percent [47,48]. GCNIS is a multifocal rather than diffuse process. Therefore there will be a higher chance of a false negative (ie, missing the lesion) when using a relatively small biopsy.

Given the possibility that small, single biopsies might miss foci of GCNIS, some authors have recommended larger specimens or double biopsies, although this practice has not been widely established. A German study of 2318 patients noted an 18 percent increase in diagnostic yield with a second biopsy as well as a 31 percent discordance among biopsy pairs from the same testicle [49]. Needle core biopsy and aspiration are not an adequate substitute for an adequate biopsy for detection of GCNIS [50].

The pathologic diagnosis of GCNIS is usually established on light microscopic examination of testicular tissue with or without immunohistochemical (IHC) staining. Proper fixation of the biopsy specimen is crucial. Formalin may not be the best fixative for preservation of the cell morphology, but it is acceptable for the diagnosis of GCNIS. Although other fixatives including Bouin or Stieve solutions may provide better cell morphology, they may interfere with immunoreactivity of some markers.

Histologic appearance — Histologically, testicular GCNIS is characterized by proliferation of enlarged neoplastic germ cells with large hyperchromatic nuclei, often one or two prominent nucleoli, and clear cytoplasm (picture 1), which gives the appearance of "fried eggs." Sertoli cells are often displaced luminally. Affected seminiferous tubules almost always lack active spermatogenesis and usually have thickened peritubular basement membranes. The interstitium may show hyperplasia of the Leydig cells. It is common for GCNIS to spread into the rete testis in a pagetoid fashion.

A negative biopsy performed before puberty does not exclude a subsequent risk of testicular cancer. Although GCNIS can be occasionally seen in the testes of prepubertal individuals, the histologic diagnosis can be challenging because normal infantile gonocytes resemble GCNIS cells.

Immunohistochemical staining — IHC can help to establish the diagnosis of GCNIS [51]. Immunohistochemically, GCNIS cells share many characteristics of testicular GCT cells. Some of the markers seen in GCNIS can be found in invasive testicular GCTs; therefore, these markers can only be used to distinguish GCNIS from benign testicular conditions and not from other invasive GCTs.

Placental-like alkaline phosphatase (PLAP) is one of the most sensitive but least specific markers for GCNIS since this enzyme is detected in almost all subtypes of neoplastic germ cells (GCNIS, seminoma, and nonseminomatous GCTs), but usually not in normal germ cells, except at the embryonal stage. Approximately 97 percent of cases of GCNIS can be diagnosed with positive PLAP staining. (See 'Pathogenesis' above.)

Another useful diagnostic marker is octamer binding transcription factor 4 (OCT4, also called POU domain class 5 transcription factor 1, or POU5F1). OCT4 is expressed in embryonic stem and germ cells and is involved in the initiation, maintenance, and differentiation of pluripotent and germline cells during normal development. In the adult testis, positive immunostaining for this marker is a strong indicator of the presence of GCNIS, seminomas (other than spermatocytic tumor [spermatocytic seminoma]), or embryonal carcinoma [52,53]. Other subtypes of GCTs, such as yolk sac tumor, choriocarcinoma, and mature and immature teratomas, do not show OCT4 immunoreactivity.

C-kit (CD117), a tyrosine kinase receptor, is another useful marker because its immunoreactivity can be seen in GCNIS and seminoma. Other nonseminomatous GCTs [19] or benign germ cells and sex stromal cells in the adult testis do not show the distinct membranous c-kit immunostaining (picture 2).

Other monoclonal antibodies, including M2A, 43/9F, and TRA-1-60, that recognize common epitopes shared by GCNIS and GCT have been reported as helpful stains for GCNIS with high sensitivities in the literature [54-56]. However, immunostaining with these antibodies is not used in routine clinical practice, possibly due to heterogeneous or inconsistent staining patterns in GCNIS [23].

Cytogenetic abnormalities — Abnormalities involving the short arm of chromosome 12, both isochromosome 12 p [i(12p)] and gain of 12p sequences, are the most common chromosomal changes found in testicular germ cell neoplasia, including GCNIS [57]. (See "Anatomy and pathology of testicular tumors", section on 'Molecular markers'.)

Noninvasive tests — Radiographic imaging has a limited role in the diagnosis of GCNIS. In high-risk populations, an irregular echo pattern on testicular ultrasound is used to exclude a hypoechoic lesion that may represent a GCT [58,59]. In one series of 78 males with unilateral testis cancer, testicular ultrasound preceded biopsy of the contralateral testis [60]. Eight of nine males with GCNIS had an irregular or coarse echogenic pattern; however, the predictive value of this finding for GCNIS was only 22 percent.

Semen evaluation for abnormal cells is an evolving technique. Characteristic malignant germ cells can be detected in the semen of males with GCNIS using IHC, DNA flow cytometry, and DNA in situ hybridization [61,62]. In addition, both i(12p) and overrepresentation of 12p sequences have been demonstrated in the semen of males with GCNIS by fluorescence in situ hybridization [63]. These noninvasive tests are promising for diagnosis of GCNIS in the future, particularly as a diagnostic strategy in prepubertal males and high-risk groups, but their clinical utility remains to be established. The limitation of these non-tissue-based tests is the difficult to distinguish GCNIS from seminoma even with a positive result.

NATURAL HISTORY AND MANAGEMENT

Natural history — The natural history of GCNIS may or may not be progression to invasive GCT including seminoma or nonseminomatous GCT, although rare reports exist of "burned out" GCNIS [14]. The frequency and rate of progression are variable. Studies performed in infertile males and in those with unilateral testicular tumors undergoing contralateral testis biopsy suggest that 50 percent of such males, if untreated, develop "invasive" tumors within five years [5,7] and 70 percent within seven years. However, "invasion" is defined as invasion of the basement membrane, which is distinctly different from actual testicular cancers.

Although the natural history and significance of GCNIS have become clearer, the management of testicular GCNIS remains controversial, particularly in males with unilateral testicular GCTs. In Scandinavia and other European countries, it is believed that all untreated cases of GCNIS will eventually progress to invasive testicular GCTs. As a result, routine contralateral biopsy and aggressive treatment of GCNIS, such as radiation therapy (RT), is practiced [46]. However, in the United States, contralateral biopsy is usually not recommended. The clinical significance of GCNIS, particularly the dichotomy in its management, will be reviewed here.

Management — Management of a patient with testicular GCNIS depends upon the clinical context in which GCNIS is diagnosed.

Unilateral GCNIS — In some European countries, orchiectomy or RT has been offered for unilateral germ cell neoplasia in situ (GCNIS) in males with a well-functioning contralateral testicle [47]. However, in North America, we do not recommend any radical treatments, such as orchiectomy or RT, in this setting. Most males with this diagnosis of GCNIS alone are followed conservatively. As previously discussed, very few males will progress to frank invasive malignant GCTs, and the therapy has substantial side effects, especially relative to fertility.

Bilateral GCNIS or GCNIS in a solitary testis — The optimal therapy is controversial in males who elect RT for bilateral germ cell neoplasia in situ (GCNIS) or GCNIS in a solitary testis. Low-dose RT (18 to 20 Gy) can eradicate GCNIS [28] as evidenced by postradiation biopsies revealing only Sertoli cells [64,65]. However, a significant number of patients will require hormone replacement therapy [66]. (See "Testosterone treatment of male hypogonadism".)

Although lowering the radiation dose to 14 or 16 Gy decreases the incidence of infertility and may preserve testosterone production [67,68], at least two reports document relapse of GCNIS with the use of these doses [69,70].

Close surveillance is an option in this setting as well, but requires that a patient be compliant with follow-up and regular testicular self-examination [28]. When this approach is chosen, periodic testicular self-examination and close follow-up by the clinician are recommended.

Contralateral testis after germ cell tumor — The optimal management of the contralateral testis in males who undergo treatment for a testicular GCT is evolving. All males should be instructed in testicular self-examination. The role of testicular biopsy of the contralateral testicle is controversial, and it is generally not performed in the United States. (See "Approach to the care of long-term testicular cancer survivors".)

The divergence in approaches begins with whether or not to perform a biopsy of the contralateral testis at the time of orchiectomy. For males who do not undergo a contralateral biopsy, the incidence of GCNIS and the risk of progression of GCNIS to invasive GCTs are not clear. (See 'Indications for biopsy' above.)

●In North America, a conservative approach is generally adopted, without immediate contralateral biopsy. Close surveillance is required, including periodic testicular self-examination and close follow-up by the clinician. This approach is supported by the observations that the rare patient who does develop a metachronous second primary cancer in the contralateral testicle has a very favorable prognosis with current treatment regimens, with cure rates approaching 100 percent.

●In some European countries, biopsy of the contralateral testis at the time of the original orchiectomy is generally advocated.

•The absence of GCNIS should provide assurance that the patient's cancer risk is not elevated above that of the general population because the false negative rate is less than 0.5 percent. If the patient has been presumably cured from his primary tumor, subsequent follow-up can be limited to five years.

•If GCNIS is identified in the biopsy specimen, males are usually offered sperm banking followed by low-dose RT if chemotherapy is not part of their original treatment regimen. Low-dose RT eradicates GCNIS and thereby prevents subsequent development of cancer.

Males with GCNIS in the contralateral gonad who are treated with chemotherapy for the primary tumor are not offered upfront RT. These patients have follow-up biopsy if indicated based upon findings on physical examination or ultrasound. Irradiation is recommended if a later biopsy documents recurrent GCNIS [71].

The efficacy of different therapeutic approaches in males who had been treated for a testicular GCT is illustrated by a German study of 228 males who had GCNIS in their contralateral testis. In this study, initial management included low-dose RT, cisplatin- or carboplatin-based chemotherapy, and surveillance. The incidence of residual or recurrent GCNIS or a metachronous second primary GCT was 3 out of 122 (2.2 percent) with RT, 37 of 96 with chemotherapy (39 percent), and 5 out of 10 (50 percent) with surveillance. Other studies have also shown that the effect of chemotherapy is unpredictable and usually temporary [72-74].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Testicular cancer".)

SUMMARY AND RECOMMENDATIONS

●Germ cell neoplasia in situ (GCNIS) is generally considered to be a precursor of all testicular germ cell tumors (GCTs), except for spermatocytic tumors (spermatocytic seminomas) in adult males and yolk sac tumors and mature teratomas in prepubertal children. GCNIS is found in the testicular tissue adjacent to a testicular GCT in more than 90 percent of cases in adults with testicular cancer. (See 'Pathogenesis' above and 'Prevalence and risk factors' above.)

●Risk factors for GCNIS include a contralateral or extragonadal GCT, androgen insensitivity syndrome or mixed gonadal dysgenesis, and possibly, cryptorchidism. The presence of any of these factors may lead to consideration of a testicular biopsy. (See 'Prevalence and risk factors' above.)

●The diagnosis of GCNIS is based upon a testicular biopsy in which neoplastic germ cells are identified within the seminiferous tubules. GCNIS does not form a mass lesion in the affected testis or cause any symptoms if not associated with other pathological conditions. In the absence of an associated GCT, the testis harboring GCNIS appears normal on physical examination and imaging studies. Furthermore, conventional serum tumor markers for GCTs are not elevated. (See 'Diagnosis' above.)

●Although GCNIS may progress to GCT, the precise risk rate and latent period are unclear; therefore, the optimal management of patients with GCNIS is controversial. A more conservative management is generally applied in clinical practice in North America. (See 'Natural history and management' above.)

•For males with unilateral GCNIS and a well-functioning contralateral testicle, the options are surveillance or orchiectomy. (See 'Unilateral GCNIS' above.)

•For males with bilateral GCNIS or GCNIS in a solitary testis, the options of low-dose (18 to 20 Gy) radiation therapy (RT) or surveillance, with attendant risks and benefits, should be discussed with the patient.

●For males with a unilateral GCT, the role of contralateral biopsy is controversial, and active surveillance or careful discussion with the patient of the relative advantages and disadvantages of active treatment is indicated. (See 'Contralateral testis after germ cell tumor' above.)

•If a biopsy is performed and GCNIS is identified, the options include surveillance, chemotherapy, or low-dose RT. For those not receiving chemotherapy, low-dose RT is effective in eradicating GCNIS. For those males whose initial treatment included systemic platinum-based chemotherapy based upon risk stratification, careful surveillance is indicated since chemotherapy is only partially effective in eradicating GCNIS.

•For males not undergoing a biopsy, surveillance is recommended. Patients should be instructed in periodic testicular self-examination.