S-100 protein content of dermal and oral mucosal blue nevi

Plaque-Type Blue Nevus of the Oral Cavity

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.

S100 protein in oral biology and pathology

The demonstration of S100 protein is used extensively for both research and diagnostic purposes in oral biology and pathology. This article reviews the structure and putative function of S100, technicalities of S100 immunohistochemistry, the cells of the oral and perioral tissues which express S100 and the possible significance of S100 expression in disease.

Oral melanocytic lesions: differences in expression of HMB-45 and S-100 antigens in round and spindle cells of malignant and benign lesions

Immunohistochemistry and melanin bleaching were used to assess the expression of antigens identified by anti-S-100 and anti-HMB-45 antibodies on melanomas and intramucosal and blue nevi from the oral mucosa of 18 patients. Both antibodies reacted with cells in all three types of lesions, but there were differences in the expression of these antigens between the round and spindle cells within the lesions. In melanomas composed of round cells, the intensity and distribution of staining with HMB-45 was greater than with S-100. The opposite was true in melanomas composed of spindle-shaped cells, and one spindle-cell melanoma was HMB-45-negative. The round cells of intramucosal nevi expressed S-100 more intensely and more frequently than HMB-45. The spindle-shaped cells of blue nevi strongly expressed both S-100 and HMB-45. Whereas intradermal nevi from the skin do not express HMB-45, intramucosal nevi consistently express this antigen in the lesion and overlying mucosa. Oral melanomas composed of round and spindle-shaped cells show differences in their expression of S-100 and HMB-45 antigens, making the use of both antibodies complementary in the diagnosis of undifferentiated tumors.

Immunohistochemical localization of S-100 protein and its subunits in melanotic lesions in the oral mucosa and skin

Immunohistochemical localization of S-100 protein, S-100 alpha and beta subunits was examined in 23 pigmented nevi, 20 malignant melanomas and 8 metastatic melanomas originating from the oral mucosa and skin. Primary oral mucosal melanomas demonstrated no beta subunit immunoreactivity while one metastatic lesion from oral melanoma that showed only a small number of melanoma cells reacted with the beta subunit. In contrast, most cutaneous melanomas and their metastatic lesions showed immunoreaction with the S-100 beta subunit. As for pigmented nevi, immunoreactions with the three antibodies were frequently detected regardless of the site. The differences in the expression of S-100 protein beta subunit between cutaneous and mucosal melanomas may be related to differences in inductive interactions between the melanoma cells and the connective tissues and skin and mucosa.

Benign conjunctival melanocytic lesions. Clinicopathologic features

The common acquired conjunctival nevus usually undergoes progressive maturation and only exceptionally gives rise to conjunctival melanoma. Pure junctional nevi are rare except in childhood. Histologically, however, a junctional nevus may be indistinguishable from primary acquired melanosis (PAM) with atypia, a condition of middle-aged and elderly individuals that has a tendency to evolve into melanoma. Nevi in adolescents may attract a vigorous lymphocytic response and may cause clinical and histologic confusion with other entities, particularly a regressing nodule of melanoma that occurs predominantly in adults. Rarely, congenital conjunctival nevi are identified, sometimes in patients with adjacent congenital nevi of the eyelid. A variety of unusual nevi, including balloon-cell nevi, Spitz nevi, epithelioid cell nevi, dysplastic nevi, recurrent nevi, episcleral melanosis and the nevus of Ota, blue and cellular blue nevi, melanocytoma, and composite or mixed nevi all may be identified in the conjunctiva. Concepts of histogenesis as well as the clinical, light microscopic, and ultrastructural features of these and other benign pigmentary conditions of the conjunctiva are described.