Clinical, microscopic, ultrastructural, and histochemical characteristics of a primary cutaneous tumor, identified as an APUDoma possibly arising from Merkel cells, are presented. The tumor can be diagnosed by means of routine histology. In some cases the argyrophylic staining technique can be helpful. The dermatological and histological aspects of this tumor suggest a highly malignant undifferentiated process. The biological behavior of this tumor, however seems to be of a low-grade malignancy. It is therefore important to recognize it from undifferentiated, highly malignant, mostly metastatic processes in the skin. There is also a summary of the clinical history and microscopic findings of identical tumors in 4 other patients.

A histological study of 14 eccrine poromas in 14 different patients was conducted and the results correlated with the clinical data. Histologically, an eccrine poroma is an easily recognizable epithelial skin tumor. Three morphological variants can be identified: a benign, a premalignant or dysplastic, and an invasive, malignant form. These tumors hardly have a typical clinical appearance. Symptoms such as bleeding, pain and itching are suggestive of a possible malignant transformation. There seems to be a predilection for localization on the limbs and the head. Most of the lesions occur in patients above the age of 60. It is noteworthy that these tumors, at least those of the face, occur on actinically damaged areas.

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The histological features of biopsies from 18 previously unreported cases of Sweet's syndrome are reported. The dermal infiltrate in the majority of the cases contained numerous histiocytes that at first sight appeared to mimic neutrophils. The immunophenotype of these histiocytes was consistent with monocytes that have freshly infiltrated into the lesions. Only two of the cases in this series, associated with leukaemia, displayed the histological features of Sweet's syndrome with a predominant neutrophilic infiltration. We suggest that the initiating mechanisms in Sweet's syndrome are that monocyte/histiocyte-derived cytokines such as the interleukins IL-1 and IL-8, secreted either by infiltrating histiocytes in the non-leukaemia-associated cases of Sweet's syndrome or by tumoural myelomonocytic cells in those associated with leukaemia, are responsible for the systemic manifestations and the infiltration with neutrophils in the skin lesions.

Hutchinson-Gilford syndrome is an extremely rare disorder of which the full clinical spectrum becomes evident with time. Sclerodermatous changes in the infant can be the first manifestation.