NEUROENDOCRINE CHARACTERISTICS OF HUMAN LEYDIG-CELL TUMORS

The neuroendocrine nature of a subset of Leydig cells has already been established. The present investigation deals with neuroendocrine char acteristics of Leydig tumour cells. A number of neuroendocrine and neu ronal markers were demonstrated in Leydig cell tumours of 7 men aged 2 5-41 years. The following substances were immunocytochemically tested in Leydig tumour cells: the mo no amine-syn the sizing enzymes tyrosin e hydroxylase and aromatic L-amino acid decarboxylase, the indoleamine serotonin, the calcium-binding protein parvalbumin, the microtubule a ssociated protein-2, neurofilament protein 200, synaptophysin, neuron specific enolase, substance P and neuronal nitric oxide synthase (NOS) . Compared to the normal interstitial cells beyond the tumours, all ne oplastic cells showed a significantly weaker immunoreactivity for nerv e cell markers as well as for testosterone and cyclic guanosine monoph osphate (cGMP), which is usually accumulated by nitric oxide (NO). Thi s provides evidence for a certain dedifferentiation of Leydig tumour c ells. However, these results suggest that tumourous development of Ley dig cells does not include loss of neuronal phenotype. Moreover, on th e assumption that 'neuronal' Leydig cells exist beside 'non-neuronal' ones in normal testicular tissue, we propose the hypothesis that 'neur onal' Leydig cells can transform to tumour cells.