A 67-year-old woman presented with a scaly, erythematous plaque, for which a clinical diagnosis of Bowen's disease was made. However, incisional biopsy established the diagnosis of amelanotic superficial spreading malignant melanoma. Biopsy thus avoided the use of inappropriate destructive therapy, such as cryotherapy or cautery. This case illustrates the importance of obtaining a histological diagnosis, prior to treatment, in suspected cases of Bowen's disease.

We report two cases of regressing cutaneous lymphoma. The first case is a CD30-positive T-cell lymphoma with immunogenetic evidence of clonality. The second case is a diffuse large-cell non-Hodgkin's lymphoma of B-cell lineage in which clonality was established by immunogenetic analysis and in situ hybridization for light-chain mRNA.

HLA‐DR expression was examined in 50 consecutive primary cutaneous malignant melanomas with a Breslow depth > 2 mm using two well‐characterized monoclonal antibodies which detect fixation‐resistant epitopes. In 31 of these cases (62%) a subpopulation of tumour cells was reactive, although there was considerable heterogeneity. Positive labelling did not correlate with depth but was associated with a reduced likelihood of developing early metastatic disease and a tendency for better overall survival, particularly in male patients. These findings contrast with earlier studies using cryostat sections and one study on paraffin‐embedded tissue in which HLA‐DR expression was shown to be a poor prognostic factor, but are consistent with the findings in other malignant tumours studied. The significance of HLA‐DR expression as a marker of prognosis may depend on the type of tissue preparation, the sensitivity of the immunocytochemical techniques used and the method of assessment.

The encapsulation of islets of Langerhans in alginate-poly-l-lysine has been proposed as a method for the immunoprotection of transplanted islets. Although several capsule compositions have been reported, there has been no published study concerning the effect of capsule composition on the severity of the foreign body reaction. Empty capsules were prepared from high mannuronic acid alginate and were coated with: (1) poly-l-lysine alone, (2) poly-l-lysine plus high guluronic acid alginate, or (3) poly-l-lysine plus high mannuronic acid alginate. The capsules were placed in the renal subcapsular space or the peritoneal cavity, and retrieved after three weeks of histological examination. The recipients were WAG/01a, nude (athymic), diabetic BB, and non-diabetes prone BB rats. The severity of reaction to the capsules was determined by measuring the thickness of the pericapsular cell infiltrate or by a scoring system. The severity of the reaction to the capsules was strain-dependent in both the renal and peritoneal sites, with the BB and nude rats displaying the most severe responses. The degree of response was not affected by capsule composition in the renal subcapsular space, but in the peritoneum, the high mannuronic acid alginate capsules provoked the weakest response, and this type of capsule will be used for future transplantation work. The infiltrating cells were characterised by immunohistochemistry and electron microscopy and found to be mostly fibroblasts and macrophages.

Islets of Langerhans were isolated from WAGola rats and encapsulated in high mannuronic acid sodium alginate droplets. The capsules were completed in the following ways: (a) poly-l-lysine alone, (b) poly-l-lysine plus high guluronic acid alginate, (c) poly-l-lysine plus high mannuronic acid alginate. Islet viability was assessed every 3-4 days over a period of 4 weeks, by a microfluorometric assay using fluorescein diacetate and propidium iodide, and every 7 days by perifusion. The perifusion results were corrected for DNA content to take islet size differences into account. The results from the microfluorometric assay showed a generally high viability of the islets in all groups at each time interval. The perifusion experiments showed that the response time and stimulation indices of the islets was similar in all groups, but the absolute amount of insulin released was slightly lower from encapsulated islets relative to unencapsulated controls. It was concluded that the presence of a capsule, regardless of its composition, did not adversely affect the membrane integrity of the islets, their response time, nor their proportionate increase in insulin release following glucose stimulation. However, the absolute amount of insulin released from encapsulated islets was reduced during perifusion. This reduction was apparent after 1 week in culture, but remained stable thereafter.

Two monoclonal antibodies, TAL-IB5 and LN3, directed at epitopes of HLA-DR were applied to a variety of benign naevi and malignant melanomas. Of the 31 naevi examined, 28 were completely unreactive. Weak staining was confined to a few cells in two intradermal naevi and there was more widespread reactivity in a halo naevus. Seven of the 25 primary cutaneous malignant melanomas were reactive with one or both of the antibodies and this reactivity was more marked in the deeper lesions. These positive cases were not felt to present diagnostic difficulties and it was concluded that TAL-IB5 and LN3 were not of use in distinguishing between benign and malignant melanocytic proliferations.