Bullous melanoma: a rare variant of melanoma causing practical problems in determination of tumor thickness.

Bullous melanoma represents a rare variant of melanoma characterized by variably large subepidermal, basilar, or suprabasilar blisters. We present 7 cases of bullous melanoma (M:F = 4:3; median age, 57 years; age range, 38-86) located on the heel (n = 2), foot (n = 2), arm (n = 2), and back (n = 1). In 5/7 cases, the bulla was due to dyscohesiveness of basilar or suprabasilar melanocytes with subsequent acantholytic features simulating pemphigus vulgaris or Hailey-Hailey disease, whereas in the last 2 cases a subepidermal bulla without clear-cut relation to the melanocytic complexes was observed. Direct and indirect immunfluorescence studies performed in 4 patients on skin near the original surgical scar (including those with subepidermal bullae) were negative. Measurement of the Breslow index in all 7 cases was affected by the presence of the bulla, and in 5 of them, the TNM classification was different depending on the method of measurement (with or without the bulla). We suggest that the Breslow index in these cases should be measured detracting the thickness of the bulla from the total thickness, but follow-up data on larger numbers of patients are necessary to establish whether the presence of bullous features has any prognostic implication.