Is Testicular Cancer on the Testicle or the Sack?

Testicular cancer grows inside the testicle itself, the egg-shaped gland, not on the outer skin commonly called the “sack” (the scrotum). The distinction matters because a lump felt within the firm body of the testicle raises much more concern for cancer than a lump on or attached to the scrotal skin, which is almost always something else entirely. About 95% of testicular cancers are germ cell tumors, meaning they arise from the sperm-producing cells deep inside the testicular tissue.¹ Understanding where the cancer actually sits helps make sense of everything from self-exams to treatment decisions.

The Testicle and the Scrotum Are Different Structures

The scrotum is a pouch of skin and muscle that holds and protects the testicles. Each testicle hangs inside it, connected to the body by the spermatic cord, which carries blood vessels, nerves, and the tube that transports sperm. When people say “testicular cancer,” they mean cancer that starts inside the testicle, the gland itself. The scrotum is just the housing. Think of it like the difference between the eyeball and the eyelid: same neighborhood, very different tissues, and very different diseases when something goes wrong.

This anatomy matters because the cells lining the scrotal skin are ordinary skin cells, while the cells inside the testicle are highly specialized reproductive cells. Testicular cancer overwhelmingly arises from germ cells, the precursors of sperm. These cells can undergo abnormal changes that begin even before birth, eventually progressing through a precursor stage called germ cell neoplasia in situ before becoming a full-blown tumor.² Cancer of the scrotal skin does exist, but it is an entirely different disease with different causes, different biology, and a different history.

What a Testicular Lump Actually Feels Like

Testicular cancer most commonly shows up as a painless lump or swelling within the testicle. If you’re doing a self-exam, you typically roll the testicle gently between your thumb and fingers. A normal testicle feels smooth and firm, roughly the size and shape of a small egg. A cancerous mass usually feels like a hard, fixed area within the body of the testicle itself, not on the surface of the scrotal skin and not in the soft tissue between the testicle and the scrotum.³

Many lumps in the scrotal area are not cancer. Cysts on the epididymis (the coiled tube sitting behind the testicle), varicoceles (swollen veins), and hydroceles (fluid buildup around the testicle) are all common and benign. These tend to feel different from a hard mass embedded inside the testicle: epididymal cysts are soft and separate from the testicular body, varicoceles often feel like a bag of worms above the testicle, and hydroceles create a diffuse swelling around the gland rather than a discrete hard spot within it. The key red flag is a firm, painless lump that you can feel is actually part of the testicle, not something sitting outside it.

Why Intratesticular Versus Extratesticular Matters So Much

When a doctor evaluates a scrotal lump, one of the first questions is whether the mass is inside the testicle or outside it. This single distinction changes the entire clinical picture. Masses inside the testicle carry a real risk of malignancy. Masses outside the testicle, in the epididymis or scrotal wall, are almost always benign.

Ultrasound is the standard tool for making this call. High-resolution scrotal ultrasound can reliably tell whether a mass is intratesticular or extratesticular.⁴ Color Doppler ultrasound adds another layer by mapping blood flow, which helps characterize whether a mass looks suspicious. European urology guidelines recommend it for determining the location, volume, and blood supply of scrotal lesions.⁵ In practice, if an ultrasound shows a solid mass clearly sitting inside the testicle, the next step is usually surgery, not a wait-and-see approach.

Can the Scrotum Itself Get Cancer?

Yes, but scrotal cancer is extremely rare and has nothing to do with testicular cancer. Cancer of the scrotal skin is typically squamous cell carcinoma, the same type of skin cancer that can appear elsewhere on the body. It actually holds a peculiar place in medical history: in 1775, a London surgeon named Percivall Pott described it in chimney sweeps who were chronically exposed to soot, making it the first cancer ever linked to an occupational exposure.⁶

Today scrotal skin cancer is vanishingly uncommon. When it does appear, it looks like a skin lesion on the scrotal surface, not a lump within the testicle. It behaves like skin cancer elsewhere, with treatment typically involving surgical removal of the affected skin. The reason most people never hear about it is that it accounts for a tiny fraction of a percentage of all cancers, whereas testicular cancer, though uncommon in absolute terms, is the most common solid cancer in young men.

The Two Main Types of Testicular Cancer

Germ cell tumors make up roughly 95% of all testicular cancers and fall into two broad groups: seminomas and nonseminomas.¹ Seminomas tend to grow more slowly and usually respond very well to radiation, while nonseminomas are a mixed bag that can include several different cell types and tend to appear at a slightly younger age. Both originate in the germ cells inside the testicle.⁷

The remaining 5% are stromal tumors, which arise from the hormone-producing or structural cells of the testicle rather than the sperm-producing cells. These are usually benign, but in rare cases they can be malignant. Regardless of subtype, all of these cancers originate within the testicular tissue. None of them start in the scrotal skin.

Blood Tests That Help Pin Down the Diagnosis

Testicular cancer is one of the few solid-organ cancers with reliable blood markers. Three proteins are routinely measured: human chorionic gonadotropin (hCG, the same hormone used in pregnancy tests), alpha-fetoprotein (AFP), and lactate dehydrogenase (LDH). These markers help with diagnosis, staging, tracking treatment response, and monitoring for recurrence.⁸

Not every testicular cancer raises all three markers. Seminomas, for instance, never produce AFP, so an elevated AFP level points strongly toward a nonseminoma component. These blood tests are drawn before surgery and again afterward, which lets doctors gauge whether the tumor was completely removed and watch for any sign it’s coming back. For a cancer that starts as a lump you can feel with your fingers, having a simple blood draw that tracks its behavior is a real advantage.

How Testicular Cancer Is Treated

The standard first step is surgical removal of the affected testicle through an incision in the groin, not through the scrotum. This procedure, called radical inguinal orchiectomy, is both diagnostic and therapeutic: the entire testicle and spermatic cord are removed so the tissue can be examined under a microscope, and at the same time the primary tumor is taken out.⁹ Surgeons go through the groin rather than cutting into the scrotum because a scrotal approach could risk spreading cancer cells into different lymph drainage pathways.

After surgery, next steps depend on the cancer type and stage. Many early-stage cases need nothing beyond surveillance, meaning regular imaging, blood tests, and physical exams. Others require chemotherapy (often platinum-based drugs, which are highly effective against germ cell tumors) or radiation. The overall cure rates for testicular cancer are among the best of any cancer, even when the disease has spread. Mortality has been declining in high-income countries since the 1970s, largely thanks to improvements in chemotherapy.¹⁰

Who Is Most at Risk

Testicular cancer most commonly strikes men between their late teens and mid-thirties, though it can occur at any age. Several factors increase the risk. The strongest established one is cryptorchidism, or undescended testicle, where one or both testicles fail to move down into the scrotum during fetal development.¹¹ A large cohort study found that the risk of malignancy in an undescended testicle was roughly 11 times higher than in a normally descended one.¹² Surgical correction (orchidopexy) performed early in life reduces that risk but doesn’t eliminate it entirely.

A personal or family history of testicular cancer also raises the odds, as does having had the disease in the other testicle. Researchers have also looked hard at environmental factors. The sharp rise in testicular cancer incidence across high-income countries during the 20th century is not fully explained by known risk factors, and some researchers suspect that prenatal exposure to endocrine-disrupting chemicals may play a role.¹³ The evidence remains suggestive rather than definitive. Long-term studies are difficult to conduct because the exposures in question happen in the womb, decades before any tumor appears, and people are exposed to complex mixtures of chemicals rather than a single agent.¹⁴

Rising Rates Around the World

Testicular cancer has been getting more common in many countries for decades. Globally, incidence among adolescents and young adults rose from about 2.6 per 100,000 in 1990 to about 4.1 per 100,000 in 2021, with the fastest increase occurring between 2010 and 2019.¹⁵ The trend is not uniform everywhere. Some Central and Eastern European countries have seen particularly steep climbs, with Croatia experiencing around 6% average annual growth in incidence over a 35-year period.¹⁶

Despite rising incidence, death rates have actually fallen in countries with access to modern treatment. This divergence between more cases and fewer deaths reflects how treatable the disease is when caught and managed properly. The rising incidence itself remains something of a puzzle. Genetic factors alone cannot explain a shift happening over just a few decades, which is why environmental and developmental hypotheses continue to attract research attention.

Self-Exams and When to See a Doctor

The idea behind testicular self-examination is straightforward: because testicular cancer usually presents as a painless mass, you have a good chance of finding it yourself before it causes any other symptoms. Self-exams are well established as a recommendation for men who have a known history of testicular cancer or a prior undescended testicle. For the general population of young men, guidelines are less unified on whether routine self-exams improve outcomes, though many urologists still encourage familiarity with what your testicles normally feel like.³

If you feel a hard lump within the body of the testicle, a painless swelling, or a noticeable change in size or firmness, see a doctor promptly. Most of the time, these findings turn out to be benign. But when they aren’t, early detection gives you the widest range of treatment options and the best prognosis. Do not wait for pain: most testicular cancers are painless, and by the time other symptoms appear (like a dull ache in the groin or lower abdomen, or breast tenderness from hormone-producing tumors), the cancer may have progressed.

Life After Losing a Testicle

Because the standard treatment involves removing the entire testicle, men naturally wonder about the physical and psychological aftermath. A single remaining testicle is usually enough to maintain normal testosterone levels and fertility, though sperm banking before treatment is commonly recommended in case chemotherapy is needed afterward.

The cosmetic and emotional side is worth acknowledging. Losing a testicle can affect body image and self-esteem, particularly in younger men.¹⁷ Testicular prostheses, silicone implants placed inside the scrotum to restore a normal appearance, are available and can be inserted either at the time of surgery or later. Whether to get one is a personal decision. Some men find the prosthesis psychologically helpful; others never think twice about the missing testicle. Surgeons and support groups both emphasize that the adjustment period is real, but for most men, quality of life returns to normal relatively quickly after treatment.