No pictures this time - frankly, do you *really* want me to?
Choriocarcinoma - a malignant and aggressive germ cell cancer of the placenta, that spreads rapidly to the lungs. Happily, it's highly responsive to chemotherapy.
On the other hand, Testicular choriocarcinoma is very difficult to treat, especially, if as this stupid bastard did, you wait until the primary tumour weighs 5 kilograms.
Testicular choriocarcinoma starts off as a small tumour in the testes that promptly starts throwing out pluripotent stem cells. These stem cells get spread through the body, implanting all over the place and like teratomas - another germ cell cancer - then differentiating into a startlingly wide range of tissues. One of the tissues it emulates is placental tissue, and even tho you're male your brain, kidney, lungs or whatever tissue it's landed in happily try to treat it accordingly. Having dozens of ersatz ectopic pregnancies appearing in your vital organs is rapidly fatal - indeed, according to the Theodore Sturgeon story I was reading this in, it was originally regarded as a deadly lung disease with testicular tumours as a side effect. Altho quite often the original tumour has starved itself to death long before you notice anything wrong elsewhere. ( This was the story "When You Care, When You Love", which features a desperate attempt to raise a fetus to maturity from one of these stem cells, in an incubator made from chamois and Bakelite ).
Hopefully awareness of this and the many other varieties of testicular cancer will ensure you remain alert for them. Altho, as 2 the Ranting Gryphon points out, men are often promptly aware that something's gone wrong with their balls....