Testicular Tumours: Sex Cord - Stromal Tumours

Classification of sex cord-stromal tumours is based on diffmerentiation into Leydig or Sertoli cells.
Sex cord-stromal tumors comprise a small minority of testicular neoplasms. It remains critically important not to confuse these neoplasms with testicular germ cell or metastatic tumors, and, again, recognition of the characteristic histologic features, immunohistochemical findings, and clinical information is diagnostic. The urologist can provide the pathologist with key clinical information in the attempt to make a correct diagnosis.
Classification:
Fibromas
Granulosa cell tumor (adult, juvenile)
Leydig (interstitial) cell tumor
Mixed or Unclassified Gonadal-Stromal Tumors
Sertoli cell tumors
Tumors of Adrenogenital Syndrome Type

Abstract:
Sex cord-stromal tumors of the ovary and testis: their similarities and differences with consideration of selected problems. Mod Pathol.2005 Feb;18 Suppl 2:S81-98.
Gonadal sex cord-stromal tumors contain some of the most morphologically interesting neoplasms of the gonads and these lead to many important issues in differential diagnosis. The pathology of these tumors is reviewed with emphasis on new information, similarities and differences in the two gonads, and diagnostic problems. Sertoli cell tumors occur in both gonads being more common in the testis where they usually exhibit a lobular pattern of hollow or solid tubules. In the ovary, tubular differentiation is usually the predominant feature but the lobulation typically seen in the testis is generally not as striking. One variant of Sertoli cell tumor, the large cell calcifying form, appears to be restricted to the male gonad and in contrast to other sex cord tumors is much more frequently bilateral and is associated in many cases with unusual clinical manifestations. In both sexes, patients with Peutz-Jeghers syndrome often have distinctive gonadal pathology. In females, it is in the form of the sex cord with annular tubules whereas in males, the lesion has features that are often intermediate between those of a sex cord tumor with annular tubules and a large cell calcifying Sertoli cell tumor. Sertoli-Leydig cell tumors are more morphologically diverse than pure Sertoli cell tumors and for practical purposes are an issue only in ovarian pathology being exceptionally rare in the testis. The classification proposed by Meyer into well, intermediate, and poor differentiation, remains important prognostically. More recently, heterologous and retiform differentiation has been described. Heterologous tumors most often contain mucinous epithelium, sometimes with small foci of carcinoid or less commonly, and generally in poorly differentiated neoplasms, rhabdomyosarcoma or fetal-type cartilage. Such tumors should be distinguished from pure sarcomas and teratomas. The retiform neoplasms, which tend to occur in young females, may mimic serous borderline tumors or even serous carcinomas. Granulosa cell tumors are much more common in females and in both gonads are divided into adult and juvenile forms. In females, granulosa cell tumors and other sex cord tumors may have markedly bizarre nuclei potentially leading to overdiagnosis as more malignant neoplasms. The juvenile granulosa cell tumor of the testis tends to occur in the first 6 months of life and should be carefully distinguished from the yolk sac tumor of the testis, which usually occurs in a slightly older age group. Occasional sex cord-stromal tumors cannot be readily categorized into the Sertoli or granulosa families and are diagnosed as sex cord-stromal tumors unclassified. In females, this is a relatively common placement for a neoplasm in a pregnant patient. Unclassified tumors are overall more common in males and may entrap residual normal germ cells potentially leading to the erroneous placement of the tumor in the category of a mixed germ cell sex cord-stromal tumor. From the practical viewpoint, the most helpful immunohistochemical findings are the negative staining of sex cord tumors for epithelial membrane antigen, and positive staining for inhibin and calretinin, findings that are converse to those seen in endometrioid carcinomas of the ovary, which commonly have formations that simulate sex cord tumors.

Abstract:
Incompletely differentiated (unclassified) sex cord/gonadal stromal tumor of the testis with a "pure" spindle cell component: report of a case with diagnostic and histogenetic considerations. Pathol Res Pract. 2007;203(10):759-62. Epub 2007 Sep 11.
The group of incompletely differentiated (unclassified) sex cord/gonadal stromal tumors includes rare cases with predominant spindle cell morphology. We report a rare case of a "pure" spindle cell tumor of the testis with morphological and immunohistochemical features consistent with the diagnosis of "incompletely differentiated sex cord/gonadal stromal tumor". Given the spindle cell morphology, the differential diagnosis with other benign and malignant spindle cell lesions is discussed. The concurrent presence of some morphological and immunohistochemical features of both Leydig and granulosa cell lines in the tumor suggests its origin from a stromal stem cell, possibly capable of dual differentiation, but with an arrest of maturation at an early phase of differentiation.

Abstract:
Sex cord-stromal tumors of the testis with entrapped germ cells: a lesion mimicking unclassified mixed germ cell sex cord-stromal tumors. Am J Surg Pathol.2000 Apr;24(4):535-42.
The authors describe 10 sex cord-stromal tumors of the testis that incorporated germ cells, thereby mimicking the unclassified type of mixed germ cell sex cord-stromal tumor (MGCSCST). These neoplasms occurred in patients from 3 to 48 years old (mean age, 26 years) who presented with testicular masses. On microscopic examination, nine tumors had a combination of tubular and cord-like arrangements of sex cord cells with transition to spindle-shaped tumor cells. They were diagnosed as either unclassified sex cord-stromal tumors (n = 5) or Sertoli-stromal cell tumors (n = 4). One tumor was a pure Sertoli cell tumor. The admixed germ cells were usually at the periphery and in clusters, but occasionally were in the center or more diffuse. In nine patients the germ cells resembled spermatogonia, having round nuclei with uniform, dusty chromatin and inconspicuous or small nucleoli. None of these cells stained with a variety of markers used for neoplastic germ cells, and in one case in which the non-neoplastic Sertoli cells were strongly reactive for inhibin but the neoplastic Sertoli cells were not, all the germ cells within the tumor occurred adjacent to inhibin-positive Sertoli cells. With static cytophotometry, a diploid deoxyribonucleic acid content was found in these germ cells in the two investigated cases. In one case the germ cells had the morphologic appearance of seminoma cells and they stained positively for the markers of neoplastic germ cells. This case was interpreted as a "collision" tumor between a Sertoli cell tumor and a seminoma. The authors conclude that sex cord-stromal tumors with entrapped germ cells of the testis are more common than unclassified MGCSCSTs--a bona fide testicular example of which has not been seen by any of the authors.