Malignant melanoma re-excision specimens--how many blocks?

Wide local excision is commonly undertaken as part of the further management of cutaneous melanoma. Although the original excision is usually complete, pathologists vary considerably in their macroscopic handling and sampling of the wide excision specimens. This study evaluates the sampling of reexcision specimens and the information gained from histological examination of tissue blocks in order to develop guidelines for the handling of these specimens.

The study group comprises 219 cases of melanoma which underwent initial biopsy followed by wider excision. The macroscopic appearance, number of blocks taken and presence of residual melanoma in the wide excision specimen was assessed. Residual melanoma was detected in the wide excision specimen in only four cases out of the 167 in which the original melanoma had been described as completely excised and in these cases the detection of a residual lesion reflected either advanced local disease at the time of the original excision, or an incompletely excised extensive radial growth phase. The sampling of wide excision specimens varied (range of blocks 1-12, average 3.1) but statistical analysis showed no undersampling of the wide excision specimens in which no residual lesion was found.

These results show that detection of a residual lesion in wide excision specimens of melanomas previously completely excised is unusual and offers no additional clinically useful information. Random block taking in the absence of a macroscopic abnormality is therefore unlikely to be clinically useful. Guidelines for the gross handling of these wide excision specimens are proposed which are likely to save resources in most histopathology departments by reducing block numbers.