An immunohistochemical study of fibrous papule of the nose: 25 cases

Twenty-five cases of fibrous papule of the nose were studied by light microscopy and by immunohistochemistry using a panel of 4 cell markers. These included polyclonal antibodies against S100 protein and Factor XIII-a (FXIII-a), and 2 monoclonal antibodies, MAC 387 which labels monocyte derived macrophage cells and Ulex Europaeus Agglutinin-1 (UEA-1) a pan endothelial cell marker. An increase in the number of S100 protein positive cells, particularly in the upper dermis, was observed in 3 lesions. Melanin was identified in phagocytes in the superficial dermis in 6 lesions, including those with S100 protein positive cells. In all of the papules there was a marked increase in FXIII-a labelling of dendritic connective tissue cells, including spindle, stellate and multinucleate stellate cells. Immunoreactivity with FXIII-a was especially strong in the increased mononuclear dendritic cell population (greater than 80%) seen in the mid- and upper dermis. However, only 15% of the larger multinucleate stellate cells were immunostained with FXIII-a. The results achieved with markers to the macrophage cell series (MAC 387) or endothelial cells (UEA-1) showed no significant increase in labelling of the dermal cell population compared to normal skin taken from the nose. Our study suggests that fibrous papule of the nose, a lesion of uncertain histogenesis, probably represents a proliferative reactive process consisting mainly of dermal dendritic cells as identified by FXIII-a in most of the lesions. There is some evidence that a small percentage of the dendritic cells may represent involuted naevi and be of melanocytic origin.