MIB-1 monoclonal antibody to determine proliferative activity of Ki-67 antigen as an adjunct to the histopathologic differential diagnosis of Spitz nevi.

BACKGROUND: The histopathologic differential diagnosis of Spitz nevus (SN) from malignant melanoma (MM) may be difficult. OBJECTIVE: Our purpose was to determine the staining pattern and usefulness of MIB-1 antibody, which recognizes Ki-67 antigen in formalin-fixed, paraffin-embedded tissue, as an adjunct to the histopathologic differential diagnosis of SN. METHODS: Twenty-five compound SNs, 27 MMs, and 26 compound nondysplastic melanocytic nevi (MNs) were immunostained with the MIB-1 antibody. RESULTS: The mean counts of MIB-1--stained tumor cells of the epidermal and dermal components, both alone and together, were significantly lower in SNs and MNs than in MMs (P <.0001). The dermal counts showed the best discriminating power. In addition, the mean dermal/epidermal count ratios for MIB-1 in SNs and MNs (0.25 and 0.23, respectively) were significantly lower than the corresponding ratio (0.94) in MMs (P <.0001). CONCLUSION: MIB-1-stained tumor cell counts, especially of the dermal component, and dermal/epidermal MIB-1 count ratios may be helpful as an adjunct to the histopathologic differential diagnosis of SN.

Moesin and CD44 expression in cutaneous melanocytic tumours.

The ERM (ezrin, radixin and moesin) family members, located just beneath the plasma membranes, are thought to be involved in the association of action filaments with the plasma membrane. One of the family members, moesin, is reported to bind to CD44. Splice variants of CD44 are thought to be associated with tumour progression or differentiation. Our aim was to investigate immunohistochemically the expression of moesin together with CD44 on paraffin tissue sections of a series of melanocytic tumours. The material included 12 ordinary melanocytic naevi, six Spitz naevi, eight dysplastic naevi, six blue naevi, seven malignant melanomas in situ, 15 primary malignant melanomas, five metastatic melanomas to the skin and five lymph node metastases. In the normal skin and the melanocytic tumours the expression of moesin was largely similar to that of CD44 standard. Strong moesin staining was observed in benign melanocytic lesions and melanomas in situ. However, the expression was decreased in advanced malignant melanomas. The moesin labelling in melanoma cells was downregulated with the depth of dermal invasion. The immunoreactivity was also diminished in the skin metastases and the lymph node metastases of melanoma. These results suggest that in melanocytic tumours, the alternation in the expression of moesin may be involved in the progression of malignancy.

Expression of proliferating cell nuclear antigen in Spitz nevus.

BACKGROUND: Epithelioid and spindle cell nevus (ESN; Spitz nevus) is a histologically well-described entity. We hypothesized that the features of ESN may reflect activation by a proliferative stimulus. OBJECTIVE: Nevocytes and keratinocytes in ESN and control specimens were examined for expression of the proliferation marker, proliferating cell nuclear antigen (PCNA). METHODS: Standard immunohistochemical methods were used to examine the expression of PCNA in a series of ESN, other nevi, and malignant melanoma. RESULTS: PCNA was detected in nevocytes in a significant percentage of ESN but not in other nevi. PCNA expression was increased in basilar keratinocytes in ESN when compared with staining of basilar keratinocytes in normal epidermis. In other melanocytic nevi and noninflamed melanoma, PCNA expression in keratinocytes was similar to that in normal control tissue. CONCLUSION: Increased PCNA labeling in nevocytes and keratinocytes in ESN suggests that a growth stimulus, present within some of these lesions, affects both keratinocytes and nevocytes.