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PA28.1 | Testicular Tumors — SDL Guide (Part 4)

GCNIS and Spermatocytic Tumor — A Comparison

Two entities are often confused in examinations:

Germ Cell Neoplasia In Situ (GCNIS)

GCNIS is the obligate precursor of all invasive GCTs (except spermatocytic tumor). It is detected by:
- Testicular biopsy in high-risk individuals (contralateral GCT, cryptorchidism)
- Adjacent to invasive GCT on orchiectomy specimen

Histology: Atypical large cells with clear cytoplasm and enlarged nuclei confined within the basal compartment of seminiferous tubules, with preservation of the tubular basement membrane (no invasion). The key IHC markers are PLAP (placental alkaline phosphatase) and OCT3/4 positivity.

Natural history: ~50% of GCNIS cases progress to invasive GCT within 5 years.

High-power seminiferous tubule diagram showing atypical GCNIS cells confined to the basal layer with Sertoli cells, intact basement membrane, and lumen, alongside a brief comparison with spermatocytic tumor. — **Panel A:** High-power seminiferous tubule cross-section with atypical GCNIS cells, Sertoli cell, intact basement membrane, and tubular lumen.. **Panel B:** Basal confinement inset plus comparison of classic seminoma versus spermatocytic tumor, including GCNIS precursor status, i(12p), lymphocytic infiltrate, and age group..

Spermatocytic Tumor

Spermatocytic tumor (previously spermatocytic seminoma) is a distinct entity that must NOT be confused with classic seminoma:

Feature	Classic Seminoma	Spermatocytic Tumor
Age	30–40 years	>50 years
Precursor	GCNIS	No GCNIS
i(12p)	Present	Absent
Lymphocytic infiltrate	Prominent	Absent
Metastatic risk	Present	Negligible
Bilateral	Occasional	Occasional
Treatment	Orchiectomy ± RT/chemo	Orchiectomy alone

Spermatocytic tumor is the only testicular GCT that does NOT arise from GCNIS and is essentially benign.

SELF-CHECK

A 60-year-old man presents with bilateral testicular masses. Biopsy shows a diffuse infiltrate of large lymphoid cells with prominent nucleoli, forming sheets and replacing the normal testicular parenchyma. Which of the following is MOST likely?

A. A. Bilateral seminoma

B. B. Bilateral yolk sac tumor

C. C. Diffuse large B-cell lymphoma

D. D. Bilateral Leydig cell tumor

Reveal Answer

Answer: C. C. Diffuse large B-cell lymphoma

Testicular lymphoma is the most common testicular tumor in men over 60 years of age, and diffuse large B-cell lymphoma (DLBCL) is the most common histological subtype. Bilateral involvement occurs in 20–38% of cases — a key distinguishing feature from GCTs, which are very rarely bilateral. Bilateral seminoma is possible but rare, and seminoma typically presents in younger men (30–40 years). Bilateral Leydig cell tumor is exceedingly rare and would cause endocrine symptoms.