The mystery of the vanishing Reinke crystals

Summary Reinke crystals (RC) are pathognomonic of Leydig cells (LCs); they are thought to be rare in normal testes and to occur only in approximately one third of LC tumors. We noticed that crystals present in touch imprint and frozen sections of an LC tumor disappeared after tissue fixation. This phenomenon led us to hypothesize that their reported low frequency in normal and neoplastic LCs may be secondary to degradation/dissolution of the crystals after formalin fixation. Our review of the literature also led us to hypothesize that RC are better preserved after air-drying and alcohol fixation. We collected testicular samples from 21 autopsies including air-dried cytologic preparations and tissue samples that were fixed in alcohol or formalin. We found that RC are common in normal LC but dissolve rapidly in formalin and slowly and only partially in alcohol. The composition of RC is unknown; however, they have been reported to stain specifically for nestin, an intermediate filament expressed mainly in neural and muscle tissue. Because the crystals have only been described in androgen-producing cells, we hypothesized that the crystals may represent a crystallized form of androgenic hormones, hormone complexes, or enzymes involved in their synthesis. We performed immunostains for androgens and enzymes involved in androgenesis. We also performed nestin immunostain to confirm the previous study. The crystals stain specifically with antibodies anti-3β-hydroxysteroid dehydrogenase and are negative for the remaining androgenic enzymes, androgenic hormones, and nestin.