Spermatocytic tumor is a rare type of germ cell tumor that starts in the testicle. Germ cell tumors develop from the cells that normally go on to make sperm. Spermatocytic tumor used to be called spermatocytic seminoma, but it is a different disease from seminoma. It usually affects older men, grows slowly, and rarely spreads. Most men with spermatocytic tumor are cured by surgery alone.
This article explains what spermatocytic tumor is, how it differs from seminoma, and how doctors diagnose it. It also explains what the findings in a spermatocytic tumor pathology report mean, including the rare finding of sarcomatous differentiation.
Spermatocytic tumor usually affects men over 50, with an average age in the mid-50s. It can occur at almost any adult age, but it is rare in men under 30. Spermatocytic tumor makes up about 1 in 100 testicular tumors, although the share is higher in older men. It is found in both testicles more often than other germ cell tumors, either at the same time or years apart.
Spermatocytic tumor develops from germ cells more mature than those that give rise to seminoma. Unlike most other testicular germ cell tumors in adults, it does not develop from germ cell neoplasia in situ (GCNIS). It also lacks the extra copies of chromosome 12 found in most other testicular germ cell tumors. Instead, many spermatocytic tumors have extra copies of part of chromosome 9 and changes in genes such as FGFR3 and HRAS. Spermatocytic tumor is not linked to an undescended testicle or to the other risk factors for adult testicular cancer.
The most common symptom of spermatocytic tumor is a slowly growing, painless swelling of one testicle. Many men notice the swelling for months or even years before seeing a doctor. Spermatocytic tumor usually does not cause other symptoms because it rarely spreads.
The diagnosis of spermatocytic tumor usually begins with an ultrasound of the scrotum, which shows a solid mass inside the testicle. Doctors usually order blood tests for tumor markers before surgery. A needle biopsy of the testicle is rarely performed. Instead, the whole testicle is removed through a cut in the groin in an operation called a radical orchiectomy. The surgery removes the testicle together with part of the spermatic cord, which carries the blood vessels and the tube for sperm.
A pathologist then examines the testicle under the microscope. A spermatocytic tumor consists of sheets of tumor cells of three different sizes. It contains small cells that resemble immune cells, medium-sized cells with round nuclei, and scattered very large cells, some with more than one nucleus. Unlike seminoma, spermatocytic tumor usually has few lymphocytes and no granulomas. The pathologist also checks the surrounding testicle, where GCNIS is not seen.
Separating spermatocytic tumor from seminoma is important, because seminoma can spread and is managed differently. When the diagnosis is uncertain under the microscope, special stains help, as described in the next section. Imaging such as a CT scan of the abdomen, pelvis, and chest is often done to check for spread.
Immunohistochemistry uses antibodies to show which proteins tumor cells make. In spermatocytic tumor, pathologists use immunohistochemistry mainly to separate it from seminoma. The stains used vary between laboratories, but typical results in spermatocytic tumor include:
Not every spermatocytic tumor needs all these stains, and when the tumor looks typical under the microscope, pathologists may use only a few.
Tumor markers are substances in the blood that some germ cell tumors release. The most commonly tested markers are alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH). In spermatocytic tumor, AFP and hCG are almost always normal. Elevated AFP or hCG suggests a different type of germ cell tumor and may prompt the pathologist to examine more of the tumor. Our article on tumor markers in your blood test explains these tests in more detail.
In about 5 to 8 in 100 spermatocytic tumors, part of the tumor changes into a sarcoma. A sarcoma is a cancer that looks like connective tissue, such as muscle or fibrous tissue. Your report will describe this as a spermatocytic tumor with sarcomatous differentiation. The sarcomatous component usually consists of spindle cells, long, thin cells that grow in bundles.
Sarcomatous differentiation is the most important finding in a spermatocytic tumor report, because it changes how the tumor behaves. Unlike the usual form, spermatocytic tumor with sarcomatous differentiation often spreads, most commonly to the lungs. It responds poorly to the chemotherapy used for other germ cell tumors.
Older reports may also describe an anaplastic spermatocytic tumor, meaning the tumor cells looked more abnormal than usual. Studies show these tumors behave like the usual form, so this term is no longer recommended.
Unlike many other cancers, spermatocytic tumor is not given a histologic grade. Grade describes how different cancer cells look from normal cells, and many other cancers use it to predict behavior. For spermatocytic tumor, the presence or absence of sarcomatous differentiation gives more useful information. Your spermatocytic tumor pathology report will not include a grade, as expected.
The pathologist measures the spermatocytic tumor in the removed testicle and reports its greatest dimension in centimeters. Spermatocytic tumors are often large at diagnosis, because they grow slowly and cause no pain. Unlike seminoma, the tumor stage of a spermatocytic tumor does not depend on size.
Tumor extension describes how far the spermatocytic tumor has grown beyond the testicle. Most spermatocytic tumors stay within the testicle. The pathologist examines the nearby tissues to see whether tumor cells have reached any of these structures:
Growth into any structure except the rete testis increases the tumor stage (pT). Growth into the tunica albuginea, the tough capsule directly around the testicle, does not raise the stage on its own.
Lymphovascular invasion means spermatocytic tumor cells were seen inside a blood vessel or lymphatic channel. These vessels carry blood and fluid away from the testicle, so tumor cells inside them have a route to spread. Your report will describe lymphovascular invasion as present, not identified, or cannot be determined. In spermatocytic tumor, lymphovascular invasion changes the stage from pT1 to pT2, but it is uncommon.
A margin is the cut edge of tissue removed during surgery. After a radical orchiectomy for spermatocytic tumor, the most important margin is the end of the spermatic cord, which is the last tissue cut by the surgeon. Your report will describe the margins in one of these ways:
Lymph nodes are small immune organs found throughout the body. Spermatocytic tumor very rarely spreads to lymph nodes. When it does, it usually spreads to the lymph nodes at the back of the abdomen, called the retroperitoneal lymph nodes. These nodes are not removed during a radical orchiectomy, so spermatocytic tumor reports from orchiectomy rarely include lymph nodes.
If lymph nodes are removed in a later operation, the pathologist reports how many nodes were examined and how many contained tumor. The report also gives the size of the largest involved node and whether extranodal extension is present. Extranodal extension means tumor cells have broken through the lymph node’s outer capsule into surrounding tissue.
The pathologic stage of spermatocytic tumor is based on the tumor in the removed testicle (pT) and any lymph nodes examined (pN). It uses the TNM staging system in the 8th edition of the AJCC Cancer Staging Manual, which the current CAP testis protocol uses. Spread to distant organs (M) is usually determined by imaging, not by the pathologist.
The prognosis for spermatocytic tumor without sarcomatous differentiation is excellent. About 8 in 10 men have a tumor limited to the testicle at diagnosis, and spread to distant organs is found in fewer than 1 in 100. Almost all men are cured by orchiectomy. In large studies, about 95 in 100 men with a tumor limited to the testicle were alive five years later. Because most men are older, many of the deaths in these studies were from other causes.
The outlook is very different for spermatocytic tumor with sarcomatous differentiation. In published reports, nearly half of these men had spread of the cancer, and survival after spread was often less than a year. Pathologic features on a spermatocytic tumor report that are linked with a higher chance of spread include:
After confirming a spermatocytic tumor on the orchiectomy specimen, the next steps depend mainly on whether sarcomatous differentiation is present and whether imaging shows spread. For most men, the orchiectomy is the only treatment needed. Follow-up usually involves regular checkups and imaging, most often in the first two years after surgery. Radiation therapy after surgery was used in the past, but it is now rarely recommended.
For spermatocytic tumor with sarcomatous differentiation, or the rare tumor that has spread, the care team may consider surgery to remove involved lymph nodes or other sites. Chemotherapy may be considered, although this form of the tumor responds poorly to the drugs used for other germ cell tumors. A clinical trial may also be an option, and your oncologist can tell you whether any are open to you.
Because spermatocytic tumor occurs in both testicles more often than other germ cell tumors, follow-up includes checks of the remaining testicle. Removing one testicle usually does not affect hormone levels because the other testicle continues to work.