Delineation of nevus cell nests in inflammatory infiltrates by immunohistochemical staining for the presence of S100 protein

Characterization of the mononuclear infiltrate involved in regression of halo nevi

Halo nevi are characterized by progressive degeneration of nevus cells surrounded by a mononuclear cell infiltrate. We studied the morphological features of the nevus cells and the composition of the mononuclear cell infiltrate in 15 cases of halo nevi using immunohistochemical techniques and a battery of antibodies to different subsets of lymphocytes and histiocytes. Regression could be divided into four more or less identifiable stages, associated with different subsets of lymphocytes and monocyte-macrophage lineage cells. Stage I (preregression): nests of unremarkable nevus cells were surrounded by a moderate number of T lymphocytes (relatively small percentage of helper inducer T cells), occasional B cells and macrophages. Stage II (early regression): large number of T lymphocytes and FXIIIa-positive cells were in close contact with nevus cell clusters which showed ragged edges. Lysozyme-positive cells and epidermal Langerhans cells were mildly increased. Stage III (late regression): single nevomelanocytes showing mild atypia were present. Numerous T lymphocytes and macrophages positive for lysozyme, KP1 and/or FXIIIa were interspersed between the nevus cells. Increased numbers of epidermal Langerhans cells were present. Stage IV (complete regression): no nevus cells were observed and moderate numbers of T lymphocytes only remained. These results suggest that T cells, especially T-suppressor cells, and different subsets of macrophages participate in the regression of the nevi.

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.

Excision of melanoma after initial biopsy. An immunohistochemical study

An immunohistochemical method for the demonstration of S-100 protein was used to identify melanocytes in fourteen cases of malignant melanoma subsequently excised after initial punch biopsy. Although S-100 protein-containing cutaneous nerves and dermal dendritic cells could be identified within the area of dermal repair, there was no evidence of physical movement of atypical melanocytes or nevus cells downward into the scarified area. This study cannot confirm the concept that punch biopsy of melanoma physically seeds atypical cells into the dermis.