What is the difference between seminoma and nonseminoma?

Seminoma is a germ cell tumor made only of seminoma cells; it usually affects men aged 25 to 45, never produces AFP, grows more slowly and is very sensitive to radiation and chemotherapy. Nonseminoma means any germ cell tumor containing embryonal carcinoma, yolk sac tumor, choriocarcinoma or teratoma, including mixed tumors that also contain seminoma. It peaks at ages 25 to 29, often raises AFP or β-hCG, and surgery plays a larger role in its treatment.

Which tumor markers are elevated in seminoma vs nonseminoma?

Pure seminoma never raises AFP. β-hCG is mildly raised in about 10 to 30% of seminomas because some contain syncytiotrophoblastic cells, and LDH can rise with tumor bulk. In nonseminoma, AFP and β-hCG are each raised in about 40 to 60% of patients, and up to 90% have at least one raised at diagnosis. A clearly raised AFP in a tumor called pure seminoma means a hidden nonseminomatous component, so it is managed as a nonseminoma.

Which testicular tumor produces AFP and which produces β-hCG?

AFP comes from yolk sac tumor, where it is almost always raised, and from embryonal carcinoma; teratoma occasionally causes a mild rise. Pure seminoma and pure choriocarcinoma never make AFP. β-hCG comes from syncytiotrophoblasts: it is raised in nearly all choriocarcinomas, often to very high levels, in 40 to 60% of embryonal carcinomas and modestly in a minority of seminomas. Leydig cell, Sertoli cell and spermatocytic tumors usually have normal markers.

What paraneoplastic syndromes are associated with seminoma?

Two antibodies mark paraneoplastic encephalitis with testicular germ cell tumors. Kelch-like protein 11 (KLHL11) IgG, first described with seminoma, causes brainstem and cerebellar symptoms such as ataxia, double vision, vertigo and hearing loss. Ma2 (anti-Ta) IgG causes limbic, diencephalic or brainstem encephalitis. Neurologic symptoms often come before the cancer is found, so scrotal ultrasound is needed. Very high β-hCG, mainly from choriocarcinoma, can also cause hyperthyroidism and gynecomastia.

How are tumor markers used after orchiectomy?

AFP, β-hCG and LDH are measured before orchiectomy and repeated afterward. AFP should halve every 5 to 7 days and β-hCG about every 1 to 3 days. Markers that fall more slowly than expected, or rise, mean residual disease; with clear imaging this is stage IS, treated with chemotherapy by risk group. The post-orchiectomy values set the S category of the stage, and the values on the day chemotherapy starts set the IGCCCG risk group.

How are seminoma and nonseminoma treated?

Both start with radical inguinal orchiectomy; a transscrotal biopsy is avoided because it raises the risk of local recurrence and of spread to the inguinal nodes. For stage I seminoma, surveillance is preferred, with one dose of carboplatin as the usual alternative. For stage IA nonseminoma, surveillance is preferred, with retroperitoneal lymph node dissection or one cycle of BEP as alternatives. Advanced metastatic disease gets cisplatin-based chemotherapy chosen by IGCCCG risk group.

Testicular Tumor Markers: Seminoma vs Nonseminoma (USMLE)

Seminoma is a pure germ cell tumor that never makes AFP (β-hCG is mildly raised in a minority) and is very radiation- and chemotherapy-sensitive; nonseminoma contains embryonal, yolk sac, choriocarcinoma or teratoma elements and often raises AFP, β-hCG or both. So a truly raised AFP means nonseminoma, even when pathology reports pure seminoma.

LDH is the third marker: it rises with tumor bulk in both groups and is the least specific. Markers are drawn before orchiectomy and repeated afterward at intervals set by their half-lives (AFP 5-7 days, β-hCG about 1-3 days), and the post-orchiectomy values set the "S" category of the stage.

Normal markers never exclude cancer. Many seminomas, pure teratomas and low-stage nonseminomas are marker-negative, so a solid intratesticular mass still goes to radical inguinal orchiectomy.

Seminoma vs nonseminoma: the key differences

	Seminoma	Nonseminoma (NSGCT)
Definition	100% seminoma	Any nonseminoma element, including mixed tumors that also contain seminoma
Share of germ cell tumors	About half (AUA: 52-56%)	About half (AUA: 44-48%); most are mixed
Typical age	25-45; peak in the fourth decade	Late teens to early 30s; peak 25-29
AFP	Never raised	Raised in 40-60%
β-hCG	Mildly raised in 10-30%	Raised in 40-60%; very high in choriocarcinoma
Growth and spread	Slower; lymphatic, to retroperitoneal nodes	Faster; retroperitoneal nodes, but choriocarcinoma spreads early through the blood
Radiation	Very radiosensitive	Not a standard treatment
Relapse after orchiectomy alone (stage I)	About 15-20%	About 30%; about 50% with lymphovascular invasion
Outcome	Cure above 90% across all stages	Stage I cure above 99%

Any nonseminoma element, or a raised AFP, makes the tumor a nonseminoma (NCI). Teratoma resists chemotherapy, which is why surgery matters more in nonseminoma.

Tumor markers by tumor type: AFP, β-hCG and LDH

Tumor	AFP	β-hCG	Marker clue
Seminoma	Never	Mild rise in 10-30%, from syncytiotrophoblastic cells; rarely above 500-1,000 IU/L	LDH tracks bulk
Embryonal carcinoma	Often raised in mixed tumors	Raised in 40-60%	Pure form often marker-negative
Yolk sac tumor	Almost always raised, often above 1,000 ng/mL	Not a source	"The AFP tumor"
Choriocarcinoma	Never (pure form)	Raised in nearly all, often very high	Gynecomastia, hyperthyroidism
Teratoma	Usually normal; mild rise reported	Normal	Resists chemotherapy
Spermatocytic tumor	Normal	Normal	Older men
Leydig or Sertoli cell tumor	Normal	Normal	Hormone effects

How often markers are up. Up to 90% of nonseminomas have a raised AFP or β-hCG at diagnosis, 39% both (EAU); low-stage figures vary: AFP 10-40% (AUA) or 50-70% (StatPearls), β-hCG 10-30% (AUA).
β-hCG in seminoma. About 14% of stage I and half of metastatic seminomas (NCI); 10-15% (AUA); up to 30% (EAU).
LDH. Raised in about 20% of low-stage germ cell tumors; treatment decisions on LDH alone are discouraged (AUA).
False-positive AFP. Liver disease, hereditary persistence of AFP and cancers of the stomach, pancreas, biliary tract, liver or lung. Some healthy people run up to 15-25 ng/mL, so a stable AFP under 25 ng/mL should not drive treatment (AUA).
False-positive β-hCG. Assay cross-reaction with LH in hypogonadism (an intramuscular testosterone dose normalizes it), heterophile antibodies and, in case reports, marijuana (NCI, AUA).

Markers for other cancers are compared in the tumor markers breakdown.

The case

A 34-year-old man has noticed a heavy, enlarged right testicle for 3 months. It does not hurt, and he has no fever or urinary symptoms. A firm, nontender mass is felt within the right testis; it does not transilluminate, and the left testis is normal. Scrotal ultrasound shows a solid, homogeneous, hypoechoic intratesticular mass. Serum AFP is normal, β-hCG is mildly elevated and LDH is elevated. CT shows enlarged interaortocaval (retroperitoneal) lymph nodes; the chest CT is clear.

Which tumor is most likely?

A. Embryonal carcinoma B. Seminoma C. Yolk sac tumor D. Choriocarcinoma E. Leydig cell tumor F. Testicular lymphoma

Answer: B, seminoma, and why every other choice is wrong

Clue in the stem	What it tells you
Painless, firm mass that does not transilluminate	Solid intratesticular mass: cancer until proven otherwise; hydroceles and spermatoceles transilluminate
Normal AFP	Seminomas do not make AFP: the key discriminator
Mildly raised β-hCG, raised LDH	Syncytiotrophoblastic cells within a seminoma; LDH reflects bulk
Homogeneous, hypoechoic mass	Typical of seminoma; large ones can turn heterogeneous with hemorrhage or necrosis
Interaortocaval nodes	First landing zone of the right testis; the left drains first to para-aortic nodes

B. Seminoma (correct). Sheets of large cells with clear cytoplasm and central nuclei (the "fried egg" look) and fibrous septa with lymphocytes, positive for OCT3/4, c-KIT (CD117) and PLAP. Retroperitoneal nodes without distant metastases make this stage II if post-orchiectomy markers stay in the S0-S1 range.

A. Embryonal carcinoma. Tempting: it affects young men and raises β-hCG in 40-60%. But its primitive, pleomorphic CD30+ cells usually form a hemorrhagic, necrotic mass, and it occurs in up to 90% of mixed tumors while pure forms are only 2-4%. It does not have the worst prognosis, though: in US SEER registry data, pure embryonal carcinoma had lower cancer-specific mortality than mixed tumors in stages II and III. In US and German registries (2002-2006), choriocarcinoma had the lowest 5-year relative survival of any type, about 80% vs about 96% for embryonal carcinoma.

C. Yolk sac tumor (endodermal sinus tumor). It almost always raises AFP, so a normal AFP argues hard against it. It is the most common testicular malignancy in boys aged 3 or younger (median age 18 months); in adults it appears mainly within mixed tumors. Schiller-Duval bodies, glomerulus-like structures with a fibrovascular core, are diagnostic when present.

D. Choriocarcinoma. β-hCG is raised in nearly all cases, often very high, with normal AFP in the pure form. It bleeds easily and spreads early through the blood to the lungs, liver and brain. Pure forms are under 1% of testicular cancers, but it appears in up to 15% of mixed tumors. Here β-hCG is mild, the spread is nodal and the lungs are clear.

E. Leydig cell tumor. The most common sex cord-stromal tumor (1-4% of testicular tumors), with age peaks at 5-10 and 30-60 years. Androgens or estrogens cause precocious puberty in boys and gynecomastia (about 20%) or infertility in men. Markers are normal and only about 2.5% metastasize in adults, so a raised β-hCG with nodal spread does not fit. Golden-brown (lipofuscin), inhibin-positive, Reinke crystals in 30-35%.

F. Testicular lymphoma. After 50 it outnumbers primary testicular tumors; it is the most common testicular tumor at 60-80 and the most common bilateral one. Most cases are diffuse large B-cell lymphoma, which spreads to the central nervous system and the other testis. See the non-Hodgkin lymphoma breakdown.

Paraneoplastic syndromes and hormone effects

Two antibodies mark paraneoplastic encephalitis linked to testicular germ cell tumors; hCG causes two hormone syndromes.

Kelch-like protein 11 (KLHL11) IgG. First described in 2019 in seminoma-associated encephalitis. In 39 men (median age 46) it mostly caused rhombencephalitis: ataxia (82%), diplopia (56%), vertigo (54%), hearing loss or tinnitus. A testicular germ cell tumor, or microlithiasis and fibrosis suggesting a regressed ("burned-out") one, was found in 83% of those screened; the neurologic syndrome often came first.
Ma2 (anti-Ta) IgG. Limbic, diencephalic or brainstem encephalitis, with daytime sleepiness and vertical gaze palsy. In young men the tumor is usually testicular (53% of the cancers in a 38-patient series); neurologic symptoms came first in 62%.
Hyperthyroidism. hCG resembles TSH and weakly stimulates its receptor, so only very high levels matter: among men starting chemotherapy for metastatic nonseminoma, half of those with hCG of 50,000 IU/L or more were hyperthyroid, and none below. It resolves as hCG falls; a beta-blocker or antithyroid drug bridges the gap. The same biology appears in gestational trophoblastic disease.
Gynecomastia. Seen in about 5% of men with testicular cancer. hCG stimulates Leydig cells through the LH receptor, raising estrogen out of proportion to testosterone; Leydig, Sertoli and granulosa cell tumors can secrete estrogen directly.

Markers after orchiectomy: half-lives, stage IS and IGCCCG risk

After orchiectomy, each marker should halve every half-life:

$C(t) = C_0 \times \left(\frac{1}{2}\right)^{t / t_{1/2}}$

Half-lives. AFP 5-7 days; β-hCG 24-36 hours (AUA) or 1-3 days (EAU).
A slower fall or a rise means residual disease. With clear imaging this is stage IS, treated as metastatic disease by IGCCCG group once ultrasound excludes a tumor in the other testis (EAU). Values within 3 times the upper limit of normal need a confirmed rise first (AUA).
Which values count. The S category uses post-orchiectomy (nadir) values; IGCCCG risk uses values taken on the day chemotherapy starts.

S category	LDH	β-hCG (mIU/mL)	AFP (ng/mL)
S0	Normal	Normal	Normal
S1	Under 1.5 × ULN, and	Under 5,000, and	Under 1,000
S2	1.5-10 × ULN, or	5,000-50,000, or	1,000-10,000
S3	Over 10 × ULN, or	Over 50,000, or	Over 10,000

ULN = upper limit of normal; 1 mIU/mL = 1 IU/L.

IGCCCG group	Nonseminoma	Seminoma
Good	Testis or retroperitoneal primary, no NPVM, markers normal or in the S1 range; 5-year survival 96%	No NPVM, normal AFP, any β-hCG, any LDH; 95%
Intermediate	Testis or retroperitoneal primary, no NPVM, any marker in the S2 range; 89%	NPVM; 88%
Poor	Mediastinal primary, NPVM, or any marker in the S3 range; 67%	None: no seminoma is poor risk

NPVM = nonpulmonary visceral metastases (for example liver, bone, brain). Survival is from the 2021 IGCCCG update; in 1997, poor-risk nonseminoma survival was 48%. The update identified LDH above 2.5 × ULN as an extra adverse factor in both seminoma and nonseminoma.

WHO classification and histology

The 2016 WHO classification, kept in 2022, sorts germ cell tumors by origin. GCNIS-derived tumors (germ cell neoplasia in situ, formerly intratubular germ cell neoplasia) are seminoma, embryonal carcinoma, postpubertal-type yolk sac tumor and teratoma, choriocarcinoma and other trophoblastic tumors, and mixed tumors; the invasive ones carry 12p gain, often as isochromosome 12p. Non-GCNIS tumors are prepubertal-type teratoma and yolk sac tumor and the spermatocytic tumor, renamed from "spermatocytic seminoma" in 2016 because it is unrelated to classic seminoma. It affects older men (average age 54 in a population study, about 65 per ACS), usually has normal markers and rarely metastasizes.

Tumor	Microscopy	Typical stains
GCNIS	Large atypical germ cells with clear cytoplasm inside tubules	OCT3/4
Seminoma	Sheets of "fried egg" cells, fibrous septa with lymphocytes, sometimes granulomas	OCT3/4, c-KIT, PLAP; CD30 negative
Embryonal carcinoma	Primitive pleomorphic cells in sheets, glands or papillae; necrosis	CD30, OCT3/4
Yolk sac tumor	Microcystic pattern, Schiller-Duval bodies	AFP, glypican-3; OCT3/4 negative
Choriocarcinoma	Syncytiotrophoblasts and cytotrophoblasts with hemorrhage	β-hCG, GATA3
Teratoma	Tissue from at least 2 germ layers (cartilage, glands, neural tissue)	Keratin

In adult men, mature and immature teratomas are not distinguished: postpubertal teratoma can metastasize and needs surgery, while prepubertal teratoma behaves benignly. Seminoma and ovarian dysgerminoma look identical; compare the ovarian tumors mnemonic.

Who gets which tumor: ages and risk factors

Patient	Think of	Clue
Boy aged 3 or younger	Yolk sac tumor, the most common malignancy (benign teratoma is the most common tumor in young boys overall)	AFP, but hard to read under age 1
Boy aged 5-10 with precocious puberty	Leydig cell tumor	Normal markers, high testosterone
Man aged 15-35	Germ cell tumor: nonseminoma peaks at 25-29, seminoma about 10 years later	AFP, β-hCG
Man over 50 to 60, or bilateral masses	Lymphoma; spermatocytic tumor	Normal markers in spermatocytic tumor

The average age at diagnosis is about 33; 6% of cases occur in children and teens and 8% after 55 (ACS). Risk factors:

Cryptorchidism: 4-6 times the risk in the affected testis, 2-3 times after orchiopexy before puberty; seminoma is the most common tumor in an untreated undescended testis.
Family history: a father or brother with testicular cancer (about 6-fold).
Personal history: 12-fold risk in the other testis, but a 15-year incidence of only 2%.
GCNIS: found next to 80-90% of invasive tumors; about 50% progress within 5 years.
Klinefelter syndrome: mediastinal nonseminoma, which also carries a risk of hematologic neoplasia (Klinefelter cheat sheet).
Others: infertility; HIV (seminoma). Isolated microlithiasis needs no workup (AUA).

Workup and treatment outline

Solid intratesticular mass: cancer until proven otherwise. Scrotal ultrasound with Doppler, then AFP, β-hCG and LDH before any treatment. A painful, swollen testis points first to testicular torsion or epididymitis; cystic masses are covered in the hydrocele and scrotal mass cheat sheet.
Fertility counseling and sperm banking.
Radical inguinal orchiectomy with high ligation of the cord, clamped before the testis is handled. No transscrotal biopsy or orchiectomy: it risks scrotal and inguinal-node spread, and local recurrence was 2.9% vs 0.4% with the inguinal approach.
Staging: CT of the abdomen and pelvis with contrast; chest x-ray for clinical stage I seminoma, CT chest for nonseminoma or rising markers; no PET. Brain MRI for multiple lung metastases, very high hCG, poor-risk disease or neurologic symptoms.
Stage I seminoma: surveillance preferred; one dose of carboplatin is the usual alternative. Adjuvant radiation is no longer favored because of second cancers (NCI); EAU advises against routine use, and AUA lists it as a less preferred option.
Stage I nonseminoma: surveillance for stage IA, with RPLND or one cycle of BEP (bleomycin, etoposide, cisplatin) as alternatives.
Stage IIA-IIB seminoma with nodes up to 3 cm: radiation, cisplatin-based chemotherapy or RPLND; larger nodes get chemotherapy.
Metastatic disease: good risk, 3 cycles of BEP or 4 of EP; intermediate or poor risk, 4 of BEP or VIP. Residual nonseminoma masses are resected; about 45% are teratoma.
Toxicities: bleomycin, lung injury; cisplatin, hearing loss (4-8 kHz) and a fall in kidney function; etoposide, secondary leukemia with 11q23 translocations. More cancer questions are on the Hematology & Oncology hub.

USMLE traps: classic teaching vs current evidence

Trap	What's actually true
"Pure seminoma" with a raised AFP is still a seminoma	Manage as nonseminoma, unless liver disease or a stable AFP under 25 ng/mL explains it
Normal markers rule out a germ cell tumor	Marker-negative tumors are common, especially seminoma, teratoma and low-stage disease
Seminoma is radiosensitive, so give radiation	True, but surveillance is now preferred in stage I, and adjuvant radiation is no longer favored (second cancers)
Seminoma risk depends on markers	Only on sites: NPVM make it intermediate; no seminoma is poor risk
A mildly raised β-hCG means relapse	Exclude LH cross-reaction (hypogonadism), heterophile antibodies and marijuana
Leydig cell tumors are 10% malignant	Older estimates were 5-10%; large recent series find about 2.5% in adults (one study, about 10% on follow-up). Only metastasis proves malignancy
Teratoma in an adult is benign	Postpubertal teratoma can metastasize and resists chemotherapy; remove it
"Spermatocytic seminoma" is a seminoma variant	Renamed spermatocytic tumor; unrelated to GCNIS, older men

Three more practice vignettes

Vignette 2: the AFP that will not fall. A 29-year-old man has a right testicular mass. Before orchiectomy, AFP is 2,000 ng/mL; β-hCG and LDH are normal. Pathology: pure classic seminoma. Liver tests and CT of the chest, abdomen and pelvis are normal. Three weeks later AFP is 1,850 ng/mL, and the left testis is normal on ultrasound. Best management?

A. Surveillance. B. One dose of carboplatin. C. Para-aortic radiation. D. PET-CT. E. Cisplatin-based chemotherapy by IGCCCG group. F. Primary RPLND.

Answer: E. The AFP makes this a nonseminoma. Three weeks is 3-4 AFP half-lives, so the level should be about 110-250 ng/mL; 1,850 ng/mL means residual disease: stage IS (S2), treated with chemotherapy as metastatic disease. EAU sets the regimen by IGCCCG group (intermediate-range AFP: 4 cycles of BEP); other protocols give all stage IS 3 cycles of BEP. A ignores the plateau. B and C are seminoma options; radiation is not standard for nonseminoma. D: PET is not used for staging. F: primary RPLND needs normal post-orchiectomy markers (stage I or IIA).

Vignette 3: thyrotoxic, with lung nodules. A 24-year-old man has blood-streaked sputum, palpitations, tremor, weight loss and tender breast enlargement. TSH is suppressed, free T4 is high and TSH-receptor antibodies are negative. Chest CT shows many lung nodules; ultrasound, a 1.5-cm hypervascular testicular mass. β-hCG is 310,000 mIU/mL; AFP is normal. Which tumor component explains this?

A. Graves disease with an unrelated mass. B. Seminoma. C. Yolk sac tumor. D. Choriocarcinoma. E. Leydig cell tumor. F. Testicular lymphoma.

Answer: D. Very high hCG stimulates the TSH receptor and Leydig cells (gynecomastia), and blood-borne lung metastases fit choriocarcinoma. hCG above 50,000 means poor risk: brain MRI, then 4 cycles of BEP or VIP; watch for bleeding into metastases when chemotherapy starts. A: negative antibodies, and Graves disease explains neither the nodules nor the hCG (Graves disease breakdown). B: seminoma hCG is modest. C: AFP is normal. E: markers are normal. F: lymphoma affects older men.

Vignette 4: the paraneoplastic marker. A 38-year-old man has 4 months of vertigo, diplopia, ataxia and new hearing loss with tinnitus. MRI shows brainstem and cerebellar T2 hyperintensity; CSF shows lymphocytes and raised protein. KLHL11 IgG is positive. The testes feel normal. Best next step?

A. Interferon beta for multiple sclerosis. B. Scrotal ultrasound. C. Brain biopsy. D. AFP and β-hCG, stopping if normal. E. No cancer search.

Answer: B. KLHL11 IgG marks a testicular germ cell tumor, usually seminoma, which may be small or burned-out (microlithiasis and fibrosis only). A: this is paraneoplastic, not demyelinating. C does not find the tumor. D: markers are often normal in seminoma. E: a normal examination does not exclude a small or regressed tumor.

Key takeaways

AFP never comes from pure seminoma or pure choriocarcinoma. A true AFP rise means nonseminoma; first exclude liver disease and a stable AFP under 25 ng/mL.
β-hCG: modest in 10-30% of seminomas; very high in choriocarcinoma, with thyrotoxicosis, gynecomastia and blood-borne spread. LDH tracks bulk.
After orchiectomy: AFP halves every 5-7 days and β-hCG every 1-3 days; a slower fall or a rise with clear imaging is stage IS, treated by IGCCCG group.
IGCCCG: nonseminoma risk depends on site and markers; seminoma risk only on nonpulmonary visceral metastases, and no seminoma is poor risk.
Solid intratesticular mass: ultrasound, markers, radical inguinal orchiectomy; never a transscrotal biopsy.
Patterns: toddler plus AFP, yolk sac tumor; precocious puberty with normal markers, Leydig cell tumor; over 50 or bilateral, lymphoma; KLHL11 or Ma2 encephalitis, scrotal ultrasound.