You are probably referring to seminoma, it´s the most common test malignancy, as testicular cancer is the most common malignancy in young male adults between 15 and 30yold.Genetic predisposition,atrophy( shrinkage) of testes is one possible cause, and hormone fluctuation, specially high estrogen levels have been linked to it.
Ref. Campbell´s - Hormones
Sex hormone fluctuations may contribute to the development of testicular tumors in experimental animals and humans. The administration of estrogen to pregnant mice may cause maldescent and dysgenesis of the testis in the offspring ([62] Nomura & Kanzak, 1977). Similar findings have been noted in the sons of women exposed to diethylstilbestrol ([39] Cosgrove et al, 1977) or oral contraceptives ([66] Rothman & Louik, 1978). Exogenous estrogen administration has also been linked to the induction of Leydig’s cell tumors. Epidemiologic studies found relative risk rates ranging from 2.8% to 5.3% for testicular tumor in the sons of diethylstilbestrol-treated mothers ([67] Schottenfeld et al, 1980; [50] Henderson et al, 1983).
Atrophy
Nonspecific or mumps-associated atrophy of the testis has been suggested as a potential causative factor in testicular cancer. [43] Gilbert (1944) found 80 cases of testicular tumors occurring in patients with a history of nonspecific atrophy and 24 additional cases related to a previous history of mumps-associated orchitis among 5500 cases of testicular tumor. Although a causative role for atrophy remains speculative, it is tempting to invoke local hormonal imbalance as a possible cause of malignant transformation.
If you ever going ON again, despite evidence advising against ( impossible to go ON and don´t get hormonal fluctuations), don´t use HCG also, for mainly 2 reasons: - It will affect testis growth directly, possibly initiating proliferation of a dormant malignant cell ( this goes for HGH also), and second because HCG is a marker for testicular cancer recidive and if your doctors see a high HCG value they will think your cancer is back.
Good news is that cure index is almost 100%, when it did not invade tubules like you described, and inguinal radical orchyectomy is performed.
If there is anything else you want to know, a good friend of mine is the head of urologic surgery in the largest oncology hospital here in my country´and would gladly answer any question.