From the Guidelines
Leydig cell tumors are characterized microscopically by large, polygonal cells with abundant eosinophilic cytoplasm, round nuclei with prominent nucleoli, and Reinke crystals in about 30-40% of cases. The cells are typically arranged in sheets, cords, or nests, and the cytoplasm often appears vacuolated due to lipid content, reflecting the steroid-producing nature of these cells 1. The tumor stroma is usually fibrous or edematous and may contain a variable lymphocytic infiltrate. Immunohistochemically, Leydig cell tumors are positive for inhibin, calretinin, and other markers, which helps distinguish them from other neoplasms 1. Some key features of Leydig cell tumors include:
- Large, polygonal cells with abundant eosinophilic cytoplasm
- Round nuclei with prominent nucleoli
- Reinke crystals in about 30-40% of cases
- Vacuolated cytoplasm due to lipid content
- Fibrous or edematous stroma with variable lymphocytic infiltrate
- Positive immunohistochemical staining for inhibin, calretinin, and other markers. The microscopic description of Leydig cell tumors is crucial for diagnosis and differentiation from other entities, such as Sertoli-Leydig cell tumors or steroid cell tumors, which may have distinct clinical and prognostic implications 1.
From the Research
Microscopic Description of Leydig Cell Tumor
The microscopic description of Leydig cell tumor is characterized by:
- Diffuse sheets of neoplastic cells, but insular, trabecular, pseudotubular, and ribbon-like patterns can also be encountered 2
- Neoplastic cells are most often large and polygonal with abundant eosinophilic, slightly granular cytoplasm; occasionally the cytoplasm is abundantly vacuolated 2
- Presence of crystalloids of Reinke in 35% of the tumors 2
- Conspicuous nuclear atypicality and a mitotic rate ranging from less than 1 to 32/10 high-power fields 2
- Blood vessel invasion, lymphatic invasion, or both can be identified in some tumors 2
- Intracytoplasmic and intranuclear Reinke's crystals can be found, which can aid in diagnosis 3
- Reinke crystals are common in normal Leydig cells but dissolve rapidly in formalin and slowly and only partially in alcohol 4
Key Features
- The presence of Reinke crystals is a key feature in the diagnosis of Leydig cell tumors 3, 4
- The crystals stain specifically with antibodies anti-3β-hydroxysteroid dehydrogenase 4
- The composition of Reinke crystals is unknown, but they may represent a crystallized form of androgenic hormones, hormone complexes, or enzymes involved in their synthesis 4