Malignant Melanoma in Siblings

Identical twins and a fraternal triplet were studied because the identical twins developed malignant melanoma at age 53. Each had a preexisting mole, nearly identically placed on the left chest, which began to grow within 2 months of one another. The homozygosity of the twins was established with high probability by appearance, behavior, psychologic testing, deficiency of color vision, red cell typing, haptoglobin typing, dermatoglyphics, lymphocyte typing, mixed lymphocyte culture, lymphocyte transfer, and skin grafting. The concordance for cutaneous malignant melanoma as well as the congruence for the site and identity of age of onset of this tumor in these monozygotic twins clearly indicates the predominant role of genetic rather than environmental factors in the development of their cancers (congruent contemporaneous concordance). Furthermore, the observation suggests that the initial phenomenon eventually leading to malignant melanoma occurred in the conceptus prior to twinning. This finding is relevant to understanding the etiopathogenesis of malignant melanoma in man.

Melanoma in twins.Cutaneous malignant melanoma in identical twins from a set of triplets

St-Arneault

Nagel

Kirkpatrick

et al. 1970

Genetic factor in malignant melanoma

Wallace

Exton

McLeod

1971

Ceinical characteristics of the genetic variety of cutaneous melanoma in man

Anderson

1971

The characteristics of coetaneous melanoma were compared in 106 familial and 2,128 non‐familial patients. Familial patients manifested a younger age distribution, a significantly earlier average age at first diagnosis, a significantly increased frequency of multiple primary melanomas, and a significantly higher survival rate than non‐familial patients. The genetic mechanism underlying the familial type of melanoma is apparently complex and may involve several autonomic gene loci, in addition to a cytoplasmic component transmitted by an affected or carrier female. The nature of this cytoplasmic component, whether deriving from a cytoplasmic organelle or inclusion, or some other mechanism is still to be determined. The clinical and genetic characteristics were interpreted as indicating a genetic variety of melanoma, but whether it is distinct or a subdivision of the clinical and histologic types of melanoma previously identified will require further study. Awareness and recognition of the genetic variety and its clinical characteristics have important practical relevance to the early detection and control of melanoma.