TESTICULAR TUMORS I: SEMINOMA,
EMBRYONAL CARCINOMA, YOLK SAC TUMORS
Testicular cancer is the most common cancer in men 15 to 35 years old. It most commonly affects Caucasian men and is rare among men of African descent. World-wide incidence has doubled over the past 40 years, with the highest prevalence rates in Scandinavia, Germany, and New Zealand. A major risk factor for its development is cryptorchidism (undescended testicle). Other risk factors include infertility and a family history of testis cancer and possibly intersex conditions, inguinal hernia, mumps orchitis, sedentary lifestyle, and environmental exposures. They most commonly present as lumps in or hardening of the testis or as an enlargement within the scrotum due to a mass or hydrocele. They are generally painless but can be associated with increased testicular sensitivity.
Although testis cancer can
be derived from any cell type found in the testicles, more than 95% of testis
cancers are germ cell tumors. Most of the remaining 5% are sex cord–gonadal
stromal tumors derived from Leydig cells or Sertoli cells. Other tumors such as
lipomas, fibromas, adenomatoids, and sarcomas are rare. Secondary tumors from
metastatic cancer, lym- phoma, or leukemia are also rare. Adult germ cell
tumors are grouped into five general types, according to fundamental histologic
and biologic behavior patterns. Seminomas comprise 40% of germ cell tumors.
They are classified as typical (90%) or spermatocytic (10%) and are homogeneous,
lobulated, yellow, orange, or pinkish tumors that are well circumscribed but
not encapsulated. Histology reveals large, round or polygonal, uniform cells with
clear cytoplasm, distinct cell membranes, and septated architecture. Tumor
cells contain a prominent, centrally placed nucleus usually occupying about
half of the cellular volume and may be arranged in disordered masses resembling
tubules without lumen, similar to ovarian dysgerminomas (see Plate 10-22). The
stroma may contain plasma cells and lymphocytes. Eighty percent of tumors
occurring in undescended testes are seminomas. They are likely to be derived
from spermatogonial stem cells within the testis. Seminomas have little
tendency to invade the spermatic cord; they metastasize mainly through
lymphatics to retroperitoneal lymph nodes. In 10% of cases, serum hCG levels
are elevated. They are very radio-and chemosensitive. When small (1 cm) and
solitary, they may be amenable to enucleation and partial orchiectomy; however,
radical orchiectomy is needed for most tumors because of their size or number.
When treated early, active surveillance or adjuvant treatment with
retroperitoneal radiation or two cycles of cisplatin- based chemotherapy is
usually recommended, with
extremely high cure rates.
Embryonal carcinomas are the
most common type of nonseminomatous germ cell tumor, accounting for about 20%
of testis malignancies. These tumors resemble the tissues of early embryos and
are likely to be derived from a multipotent primordial stem cell. This type of
tumor can grow rapidly and metastasize. Grossly, they have the appearance of
soft tissue, with areas of hemorrhage and necrosis. Histologically, embryonal carcinomas
are composed of large masses of pleomorphic, embryonic epithelial cells that
may simulate glandular structures with papillary organization or trabecular
cells. These tumors stain with keratin, OCT-4 and CD30, are associated with an
abnormal isochromosome 12 karyotype, and may be associated with elevated serum lactate dehydrogenase and placental alkaline
phosphatase levels. Cells may be arranged into lobules or into papillary,
cystic, and other patterns of either differentiated or poorly differentiated
structures, including cytotrophoblast and syncytiotrophoblast. Treatment is by
radical orchiectomy and with either cisplatin-based chemotherapy or
retroperitoneal lymph node dissection for early-stage disease. Cure rates
higher than 90% are possible in most cases.
Endodermal sinus tumors
(yolk sac tumors) are unusual, very aggressive, malignant testis cancers. These tumors recapitulate embryonal yolk sac tissue and uniformly
secrete-fetoprotein that is measurable in serum. In pure form, they are most commonly
found in young boys; in adults, they usually occur as a component of mixed germ
cell tumors. Grossly, the cut surface is heterogeneous because of extensive
hemorrhage, necrosis, and cystic degeneration. Histologically, they are
characterized by a pleomorphic intermingling of epithelial and mesenchymal
elements (Schiller–Duval bodies) in an attempt to form yolk sac tissue.
Treatment is radical orchiectomy and cisplatin-based chemotherapy.
