[Pigmented Paget's disease of the male nipple]. / Maladie de Paget pigmentée du mamelon chez l'homme.

BACKGROUND: Mammary Paget's disease unfrequently occurs in males, and may be pigmented in rare instances. Differential diagnosis with malignant melanoma relies on immunohistochemical studies. CASE REPORT: A case of Paget's disease of the nipple in a 76 year-old male is reported, clinically mimicking a malignant melanoma because of massive pigmentation. Histologically, large Paget's clear cells were intermingled with numerous melanin-rich dendritic melanocytes. An underlying ductal carcinoma was found. After differential immunohistochemical staining, diagnosis of Paget's disease could be unequivocally substantiated since Paget's cells stained for epithelial markers, c-erbB-2 and hormonal receptors, whereas protein S100 and HMB45 were negative. DISCUSSION: Pigmentation in mammary Paget's disease occurs preferentially in males. Pigmentation results from numerous melanocytes with abundant melanin in close contact with Paget's cells. An increased number of melanocytes may also be observed in cutaneous metastatic breast carcinomas. It could result from a chemotactic factor produced by neoplastic cells.

[Demonstration of molecular forms of Rap 1 in cells or tissues deriving from normal or pathological human colonic epithelium]. / Mise en évidence de formes moléculaires de Rap 1 dans des cellules ou tissus dérivés de l'épithélium colique humain sain ou pathologique.

Mutations of the cK-ras gene which confer oncogenic properties to the corresponding encoded small G protein, occur in 30 to 50% of the human colonic adenocarcinomas. Overexpression of Rap 1A, a member of the Ras family, in K-ras transformed fibroblasts, reverts the transforming properties of the oncogene. This indicates that Rap 1A may exert antagonistic properties towards the K-Ras protein. In this respect, we have been interested in comparing Rap 1 expression in the human adenocarcinoma cell line HT29 and in safe or pathological tissues deriving from the human colonic epithelium. In the human adenocarcinoma cells HT29, several immunoreactive forms of Rap 1 of 71 kDa, 47 kDa, 40 kDa and 24 kDa are detected. Extraction in Triton X-114 allows separation of HT29 cell proteins on the basis of their differential hydrophobic properties. Parallelly, proteins were separated in crude cytosolic or membrane fractions. Most of the immunoreactive material corresponding to the 24 kDa band may contain hydrophobic and membrane associated components. The molecular nature of the higher size components is also discussed here. In the tissues, the 47 kDa form which is common in all of the safe and pathological samples considered, appears to be specifically expressed in the colon. Besides, the 71, 68 and 24 kDa were found in pathological tissues. High expression of Rap 1 was demonstrated to be correlated with cell differentiation in the safe colonic epithelium and in the adenomas. Cloning of the Rap 1A cDNA is now in progress in the laboratory, using PCR detection in an HT29 expression library.