A wide range of histologic types of testicular tumours are recognized, giving rise to many different classification schemes.
Tumours can be divided into two major groups:
1. Germ cell tumours (accounting for approximately 95% of cases)
2. Nongerminal tumours (stromal or sex cord tumours)
Most germ cell tumours are aggressive lesions, although outlook has improved considerably with current therapy.Most neoplastic scrotal masses ultimately prove to be germ cell tumours and are recognisable with routine haematoxylin and eosin-stained sections.The differential diagnosis may be focused, even before reviewing histological sections, by knowledge of patient age, medical history, tumour site (testicular vs paratesticular) and gross findings.Some cases may prove to be diagnostically challenging, including rare tumours, a common tumour with an unusual pattern, a metastatic tumour, or a neoplasm with features that mimic another tumour.Several morphological patterns are seen with some frequency and these generate recurring sets of differential diagnostic considerations. These common patterns include testicular tumours with a predominant diffuse arrangement of cells with pale to clear cytoplasm, tumours with a glandular/tubular pattern, tumours with a microcystic pattern and tumours composed of oxyphilic cells. Intratubular proliferations of atypical cells, paratesticular glandular and/or papillary tumours, or tumours with spindle cell morphology can also be challenging to diagnose correctly.In some problematic cases, immunohistochemical staining may be useful to resolve these differential diagnoses.
The following are the risk factors for testicular carcinoma:
i) Previous history of testicular tumor; ii) positive family history; iii) cryptorchidism; iv) infertility, and v) intersex syndromes (gonadal dysgenesis, true hermaphroditism, and pseudohermaphroditism). If a patient has had carcinoma in one testis, his risk for developing a contralateral tumour is more than 20 times that of the general population.A history of testicular carcinoma in a first-degree relative increases the risk factor several times.
Cryptorchidism (incomplete descent of the testicles from the retroperitoneum into the scrotum) has a strong association with testicular carcinoma. The majority of undescended testes lie distal to the external inguinal ring and are palpable. They generally descend into the scrotum by 1 year of age. Nonpalpable testicles are usually within the inguinal canal but can be anywhere along the path of descent from the retroperitoneum. Although the overall occurrence of cryptorchidism is low (<1%).
The use of immunohistochemistry in the differential diagnosis of tumors of the testis and paratestis. Semin Diagn Pathol. 2005 Feb;22(1):33-50.
Although most testicular and paratesticular tumors can be recognized by their light microscopic features, some raise significant differential diagnostic questions. Immunohistochemical staining has proved of significant value in this situation. There is still a role for the traditional markers, including placental-like alkaline phosphatase and alpha-fetoprotein, but newer markers provide additional support and often have greater sensitivity and specificity for many diagnoses. OCT4 is virtually 100% sensitive and specific for seminoma, embryonal carcinoma, and intratubular germ cell neoplasia, unclassified type. Inhibin-alpha, among testicular tumors, is limited to those in the sex cord-stromal category or those having adrenocortical-type differentiation (testicular tumor of the adrenogenital syndrome) or of trophoblastic lineage. Calretinin is another positive marker for the sex cord-stromal tumors but has less specificity. Additional markers, including differential cytokeratins, c-kit, CD30, epithelial membrane antigen, S-100, melan-A, and others, are useful in specific situations. This article reviews the application of immunohistochemical markers for a number of differential diagnostic considerations in the testis and paratestis categorized according to their light microscopic patterns.
From the archives of the AFIP: tumors and tumorlike lesions of the testis: radiologic-pathologic correlation. Radiographics. 2002 Jan-Feb;22(1):189-216.
Testicular carcinoma represents only 1% of all neoplasms in men, but it is the most common malignancy in the 15-34-year-old age group. Germ cell tumors constitute 95% of all testicular tumors. Germ cell tumors are a varied group of neoplasms whose imaging features reflect their underlying histologic characteristics. Seminomas are generally well-defined homogeneous lesions, whereas the nonseminomatous tumors (embryonal carcinoma, yolk sac tumor, choriocarcinoma, teratoma, and mixed germ cell tumor) have a much more varied appearance. Germ cell tumors follow a predictable pattern of spread via the lymphatic drainage to the retroperitoneal nodes. Choriocarcinoma, which has a proclivity for early hematogenous spread, is a notable exception. Testicular tumors may also arise from the sex cords (Sertoli cells) and stroma (Leydig cells). Although 90% of these tumors are benign, there are no reliable imaging criteria to differentiate them from malignant masses. Some benign testicular masses can be recognized, obviating an unwarranted orchiectomy. A dilated rete testis is a normal variant and appears as a series of small tubules near the mediastinum testis. Other benign lesions that can be suspected on the basis of imaging findings and history include intratesticular cysts, epidermoid cysts, congenital adrenal hyperplasia, and sarcoidosis.