Testicular Tumours: Leydig (Interstitial) Cell Tumours

Leydig cell tumours are relatively uncommon neoplasms, accounting for 2% of all testicular tumours.
They occur in two age groups (but may be found at any age) :
- Boys younger than four years of age.
- Most occur between the ages of 20 and 60 years.
The tumours elaborate androgens or mixtures of androgen and other steroids (estrogens, corticosteroids).
The endocrine effects from these interstitial cell (Leydig cell-derived) tumours in prepubertal children lead to precocoious physical and sexual development. By contrast, feminization, such as gynecomastia, is observed in some adults with this tumour.
Clinical manifestations include a testicular mass and changes referable to hormonal abnormalities.
In pre-pubertal boys there is precocious physical and sexual development.
In adults it causes gynecomastia.
Grossly, the tumors are circumscribed nodules with a homogeneous, golden brown cut surface. Necrosis and hemorrhage may be seen and cause concern for malignancy.
Microscopic features: The most common microscopic pattern is diffuse. Insular, trabecular, pseudotubular, and ribbonlike arrangements of the tumour cells are occasionally noted. Necrosis may impart a pseudopapillary appearance. The stroma may be hyalinized and occasionally edematous or myxoid. The neoplastic cells resemble normal Leydig cells in most cases. They typically have abundant eosinophilic, slightly granular cytoplasm, but the cytoplasm may be spongy as a result of lipid accumulation. Crystals of Reinke are found in approximately one third of the cases.
Microscopically, they are composed of polygonal cells with abundant granular, eosinophilic or cytoplasm and indistinct cell borders. Lipochrome pigment, lipid droplets and characteristic cytoplasmic inclusion “Reinke crystalloids” (well defined rectangular eosinophilic structure) are commonly present.
Ten percent of tumours invade, metastasize or both invade and metastasize.
-No single pathologic criterion reliably distinguishes between benign and malignant Leydig cell tumors.However, the latter are typically larger, have infiltrative margins, invade lymphatics or blood vessels, and contain foci of necrosis. They also have a mitotic rate of more than 3 per 10 high-power fields and significant nuclear atypicality much more often than benign tumors. Rarely, however, a tumour with little or no suggestion of malignancy on gross or microscopic examination metastasizes, usually late in the course of the disease.
- Perhaps the most important remains the occasional confusion of this neoplasm with the remarkable nonneoplastic entity, the so-called testicular tumour of the adrenal genital syndrome. Individual fields may be indistinguishable. A triad of microscopic findings, if all present, lead to serious consideration of the nonneoplastic lesion particularly: i) broad fibrous bands ; ii) spotty nuclear atypia without mitotic activity , and iii) cytoplasmic lipochrome pigment. The latter, when conspicuous, may result in the nonneoplastic lesion having a particularly dark brown colour. Should a mass lesion be bilateral and have any extra testicular nodularity, the nonneoplastic lesion should be strongly considered, particularly if any of the microscopic findings already noted are seen.
- Occasionally, true Leydig cell hyperplasia or at least relative prominence of Leydig cells in an atrophic testis may suggest a small Leydig cell tumour, but these are typically multifocal and separated by seminiferous tubules - this should always favour a nonneoplastic proliferation.
- Rarely, malakoplakia may be mistaken as Leydig cell tumour, but associated inflammatory cells, sometimes even abscess formation, as well as, the distinctive Michaelis-Gutmann bodies, should be diagnostic.