Regressing Merkel cell carcinoma-a case showing replacement of tumour cells by foamy cells.

Merkel cell carcinoma (MCC) is a malignant neuroendocrine tumour with a high rate of recurrence and metastasis. However, some cases of spontaneous regression have recently been reported. We describe the clinical course of an 80-year-old Japanese woman with regressing MCC. We also report histological findings of the regressing tumour for the first time. After the patient's first visit to our hospital, the lesion was a rapidly progressive tumour, but suddenly began decreasing in size, and rapidly regressed. The surface of the tumour flattened, the colour changed from red to dark red, and finally the lesion appeared as a small yellowish plaque. Histopathological analysis of the completely regressed tumour revealed that the tumour cells were completely replaced by numerous foamy cells. This is the first report demonstrating the histopathological features of regressing MCC.

Expression of neuronal nitric oxide synthase in dermal infiltrated eosinophils in eosinophilic pustular folliculitis.

Nitric oxide (NO) is produced by a wide variety of human cells and affects physiological and pathophysiological processes. In this study, we demonstrated for the first time that neuronal NO synthase (NOS) is expressed in eosinophils infiltrating into the dermis and follicular epidermis in eosinophilic pustular folliculitis (EPF). EPF is a cutaneous inflammatory follicular disorder first described in Japan. The clinical and histological features of EPF are characterized by erythematous papules, infiltration of numerous eosinophils, and a spongiotic appearance of the follicular epidermis, but the pathophysiology of EPF remains unclear. Our results suggest that NO produced from eosinophils plays an important part in the pathogenesis of EPF. Furthermore, we speculate that NOS inhibitors may be useful in the management of EPF.