The expression of c-myc protein was studied in formalin-fixed, paraffin-embedded sections of 16 compound Spitz nevi (SNs), 20 ordinary compound melanocytic nevi (MNs) and 30 malignant melanomas (MMs), using monoclonal antibody 9E10 and an immunoperoxidase technique. Nine (56%) SNs, 16 (80%) MNs and 23 (77%) MMs showed positive reactions in some of the tumor cells (P = non-significant). The staining reactions were mostly cytoplasmic, and moderate to strong in intensity. The frequencies of positively stained cells were higher in the MN and SN groups. Most of the lesions with a significant dermal component did not show stratification of staining with progressive descent into the dermis. Therefore, the mode of expression of c-myc in routinely processed specimens does not differentiate between SNs, MNs and MMs. One possible reason is that the increased expression of the c-myc protein is not sufficient alone to promote proliferation and malignant transformation in these types of tumors.

This study was performed in an attempt to further elucidate the pathogenesis of delayed postburn blistering. Two cases were studied ultrastructurally and immunohistochemically, 1 with blisters on the recipient site of autologous split-thickness skin grafts and the other on the donor site. Ultrastructurally, the basement membrane was on the roof of the blisters in both cases, except for a single small blister in the first case where it was on the dermal floor. In the blister roofs, the basement membrane showed small or marked segments of discontinuity. In the adjacent non-blistered healed skin, the basement membrane was usually continuous, and anchoring fibrils were present. Immunoperoxidase staining on frozen sections, using antibodies to laminin, laminin 5, collagen IV, and collagen VII, showed a mostly continuous linear pattern in the adjacent non-blistered skin, which often became discontinuous near the blisters and markedly discontinuous in the blister roofs. In the blister floors, weakly stained linear or granular deposits of some of these components were sometimes also present. The results of this study support discontinuity of the basement membrane as the main anomaly in delayed postburn blistering. Disturbance in the reassembly or local breakdown of the basement membrane components might be the underlying defect.

The present study was performed to determine the frequency of p53 protein immunoreactivity in classical Kaposi's sarcoma (KS) as a whole and in relation to the histological subtypes which are considered to correspond to the developmental stages of the tumor. The accumulation of p53 protein was studied immunohistochemically using monoclonal antibody BP53-12 on formalin-fixed paraffin-embedded sections of 36 KS lesions, of which 14 were classified histologically as early type and 22 as spindle-cell or mixed type. No positive immunoreactivity was detected in any of the 14 early-type lesions. Among the 22 spindle-cell and mixed variants, positive staining was detected in 5-10% of the tumor cells in one lesion, 1-5% of the cells in six lesions, and in < 1% of the cells in two lesions. These very small percentages of positively stained cells in less than half of the cases of the spindle-cell and mixed variants do not support a significant role for p53 in tumor progression and evolution in KS.

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