Neuroendocrine (Merkel cell) carcinoma of the skin: a clinico-morphological study of 13 cases.

The clinico-morphological features in 13 patients (nine female) with neuroendocrine carcinoma of the skin are presented. The mean age was 64.9 years. The limbs were the most common site of primary tumour, followed by the face. The clinical course was characterized by a high incidence of regional lymph node metastases (69%) and recurrences (46%). Seven of the patients died of tumour, with a mean survival time of 13 months. Histologically, a solid pattern of tumour growth was most common. The cells were usually small and uniform. Squamous cell differentiation was found in one tumour. The cell of all tumours reacted positively for cytokeratins and neuron-specific enolase. The positive reaction frequently had a ball-like globular pattern, corresponding to inclusion-like bodies seen on light microscopy and to paranuclear whorls of intermediate filaments observed on electron microscopy. Neurosecretory granules were seen on electron microscopy in the 11 cases examined and in one case a 'Luse body' was found in the intercellular space.