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Large or giant cellular blue nevi are usually congenital and represent a challenge for the physician. Close anatomic structures may be altered by the size of the moles. In this article, we report the case of an uncommon large, agminated, cellular blue nevus of the ‘plaque type' in a 42-year-old female. Due to the risks of malignant melanoma development on a large or giant blue nevus, we highlight the importance of proper histopathological diagnosis. Furthermore, because of the possibility that the nevus may invade the bone and cerebral tissues, we discuss the indication of a radiological diagnosis. The accurate correlation to clinical and histopathological findings and appropriate multidisciplinary management can save the lives of patients.

Background: The blue nevus of the oral cavity is a rare lesion with important differential diagnoses. The plaque-type blue nevus is an uncommon variant of the blue nevus. Because of its particular clinical appearance, it can easily be confused with satellite metastases from malignant melanoma. The diagnosis usually requires a biopsy. Objectives: To describe the clinical and histological features of a plaque-type blue nevus of the buccal mucosa in a 20-year-old white woman, to review all intraoral blue nevi and all plaque-type blue nevi reported in the literature so far and to compare the criteria of blue nevi and nevus of Ota. Results: An intraoral blue nevus was described for the first time in 1959. Since then around 70 further cases have been documented. Our case is the first report of a plaque-type blue nevus of the oral cavity. Conclusions: The exceptional widespread intraoral blue nevus described herein can clinically be confused with an intraoral malignant melanoma, and it has a very similar clinical appearance as the intraoral part of nevus of Ota. Apart from the clinical resemblance, there is also some degree of histological overlap of the dermal melanocytoses. Transitional states between blue nevus and nevus of Ota may occur clinically and histologically.

Background: Psoriasis is an immunogenetic disorder. Factor XIIIa+ dermal dendrocytes (DD) are part of the pathobiological changes in the plaque type of the disease. Objective: The present study aimed at comparing the effect of 3 vitamin D3 derivatives on the epidermis, microvasculature and DD in psoriasis. Method: Twenty men suffering from chronic plaques of psoriasis on the trunk were enrolled in this study. They applied twice a day for 3 weeks calcipotriol, tacalcitol and calcitriol, each to one plaque. Another similar lesion received petrolatum as a placebo treatment. Skin biopsies were taken at entry and at completion of the 3-week treatment phase. Immunohistochemistry was performed using the lectin of Ulex europaeus and an antibody to factor XIIIa. Computerized image analysis served to measure the stratum Malpighii area, the microvasculature area and the DD numerical density in the papillary dermis. Results: At entry in the study, the 4 test sites were indistinguishable with regard to the stratum Malpighii area, the papillary microvasculature area and the papillary DD density. The 3 histometric parameters appeared correlated with each other. At completion of the 3-week treatment phase, the 3 vitamin D derivatives had decreased the size of the stratum Malpighii. In addition, calcitriol had also reduced the DD density in the papillary dermis. No other significant changes were yielded. Conclusion: As assessed by histometry, the psoriatic epidermis responded to a short treatment using the 3 vitamin D derivatives. The better result compared to the control site was achieved by calcitriol. DD appeared to be most controlled by the same drug. The microvasculature did not appear to be decreased at the 3-week time point in treatment.