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Germ cell neoplasia in situ is the pre-cancer of testicular germ cell tumours: abnormal fetal-type germ cells sitting inside the seminiferous tubules, which will become seminoma or non-seminoma if left. It is found beside almost every testicular cancer and sometimes on its own in the other testis, where low-dose radiotherapy or surgery prevents a second cancer.
The pre-invasive lesion of postpubertal testicular germ cell tumours was recognised in the early 1970s and carried several names (carcinoma in situ, intratubular germ cell neoplasia unclassified, testicular intraepithelial neoplasia) until the 2016 WHO consensus classification united them as germ cell neoplasia in situ (Histopathology 2016; Moch 2016). The cells resemble seminoma cells, express OCT4, PLAP and KIT, lie along the tubular basement membrane in tubules without spermatogenesis, and are the origin of seminoma, embryonal carcinoma, yolk sac tumour, choriocarcinoma and postpubertal teratoma, but not of spermatocytic tumour or prepubertal tumours. Testicular biopsy is the only established way to diagnose it; serum microRNA-371a-3p, a marker of invasive germ cell tumours, was raised in 51.9 percent of 27 men with isolated GCNIS (J Cancer Res Clin Oncol 2017).
How it differs from its parent: it is not yet a cancer, is not staged and raises no conventional serum markers; its importance is the roughly one in two chance of progression to invasive tumour over five years quoted in the classification literature, which drives contralateral biopsy policies in some countries.
How common: present beside almost all germ cell tumours; isolated GCNIS has no population figure in the sources read.
Treatment: for GCNIS in the remaining testis after orchidectomy for cancer, low-dose testicular radiotherapy (which preserves testosterone production but ends fertility), orchidectomy, or surveillance in men who wish to father children; chemotherapy for the invasive tumour eradicates GCNIS incompletely, so the contralateral testis is watched (NCI PDQ testicular summary for the invasive pathways).
The precursor of almost every postpubertal testicular germ cell tumour, found in the tissue beside the tumour; as an isolated finding it is diagnosed on biopsy in men investigated for infertility, a contralateral tumour or cryptorchidism (Histopathology 2016). No incidence figure exists for the isolated lesion in the sources read.
Germ cell tumours drain along the spermatic cord to the para-aortic nodes high in the abdomen, not to the groin, which is why staging scans look at the retroperitoneum.
Same organ: Retroperitoneal germ cell tumour, Leydig cell tumour of the testis, Sertoli cell tumour of the testis, Spermatocytic tumour of the testis, Embryonal carcinoma of the testis, Yolk sac tumour of the testis, postpubertal type, Choriocarcinoma of the testis, Testicular germ cell tumours, Seminoma, Non-seminomatous germ cell tumour, Germ cell tumours of childhood and adolescence (extracranial and CNS)
Low-dose testicular radiotherapy, orchidectomy, or surveillance in men wanting children; the invasive tumour that follows is treated as seminoma or non-seminoma.
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Query for this cancer: (TITLE:"Germ cell neoplasia in situ" OR ABSTRACT:"Germ cell neoplasia in situ" OR TITLE:"GCNIS" OR ABSTRACT:"GCNIS" OR TITLE:"Intratubular germ cell neoplasia, unclassified" OR ABSTRACT:"Intratubular germ cell neoplasia, unclassified" OR TITLE:"IGCNU" OR ABSTRACT:"IGCNU" OR TITLE:"Testicular intraepithelial neoplasia" OR ABSTRACT:"Testicular intraepithelial neoplasia" OR TITLE:"TIN" OR ABSTRACT:"TIN") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Germ cell neoplasia in situ (GCNIS), not a curated reading list.
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