ABSTRACT. A new species of parasitic dinoflagellate is described from the portunid crab Portunus pelagicus. The dinoflagellate is a member of the genus Hematodinium which formerly consisted of a single species, H. perezi. Members of the genus have been reported in crabs and lobsters from Europe and North America, where in some circumstances they cause significant mortalities to host populations. The new species 1s the first member of the family Syndinidae to be fully described from Australia. The new species differs from other forms of Hematodinium primarily by the size of the trophont (vegetative stage), the ovoid plasmodium, and the small beaded form of condensed chromatin in the nucleus. Infection experiments indicated that the parasite may be transmitted within and between the 2 host species. In addition, the pre-patent period of the new form was at least 16 d which is much greater than that reported from other forms.

The outcome of treatment in 40 black patients (27 women, 13 men; mean age 62.9 years) with plantar melanoma over a 13-year period was analysed to evaluate the efficacy of wide local excision with split skin grafting. Substantial delay in seeking medical attention occurred in 35 patients. At presentation, 20 patients had stage I disease, one stage II, 15 stage III and four stage IV. Acral lentiginous melanoma (27 patients) was the most common histological type. The mean Breslow depth was 6.9 mm and 35 patients had lesions of Clark level IV or V. The mean surface area or plantar lesions was 13.3 cm2. Wide local excision with split skin grafting was used in 29 patients; four patients with neglected advanced plantar lesions had below-knee amputation and seven with metastatic disease did not undergo surgery. Graft sepsis occurred in six patients and local recurrence in two. Nine patients were alive at follow-up; the 5-year survival rate was 25 per cent. Delay in presentation and locally advanced disease may explain the poor prognosis of plantar melanoma in black South Africans.

Little is known about the behaviour of melanoma in patients of mixed ancestry. A retrospective analysis of 844 consecutive patients presenting with melanoma over a 12-year period was performed. Forty patients (4.8%) were of mixed ancestry. The data evaluated included patient age, gender, delay in presentation, presenting stage, anatomical distribution, histology, management and outcome. The mean age at presentation was 52.8 years. Twenty-seven patients were female. The mean delay in presentation was 1.54 years. Seventy per cent of melanomas were confined to the extremities, of which one-third were plantar in origin. The most common histological variant, affecting 13 patients (32.5%), was acral lentiginous melanoma; 12.5% of patients presented with in situ (Stage 0) disease, 17.5% with Stage I disease, 22.5% with Stage II disease, 27.5% with Stage III disease and 7.5% with Stage IV disease. Twenty-seven patients (67.5%) remained alive at the end of the study after a median follow-up of 5.58 years, whilst 11 (27.5%) died after a median of 2.42 years. The median survival was 3.92 years. Although the histological type and anatomical distribution reflect the disease pattern of black populations, the overall 5-year survival of 74% is similar to that seen in white populations. An education programme is needed to improve melanoma awareness in mixed race populations.

Recent studies have shown that narrower excision margins may be safe, but the optimal or minimum margin for melanoma is unknown. Wide margins of excision are possible on the trunk and limbs, but functional and cosmetic constraints often limit the extent of excision on the face. A collaborative study from two continents (Cape Town, South Africa and Northwood, England) investigated the outcome of different excision margins of 106 patients with stage I melanoma of the face. The margin of excision was measured from the records of the pathological specimen. Thirty patients had margins of less than 1 cm, 64 had margins of between 1 and 2 cm, and 12 had margins greater than 2 cm. Primary apposition or flap closure was possible in 85 patients. Seven patients developed local recurrences and these were not influenced by the excision margin. This study supports the contention that the primary treatment of cutaneous melanoma on the face should be histologically confirmed complete excision, and that this can be achieved with margins of excision less than 1 cm. Local recurrence is not related to the margin of excision or to tumour thickness.