(Background) The treatment for melanoma of thumb is challenging field, because of poor prognosis, and the varying length and volume of the lost thumbs. Melanoma should be excised or amputated with enough surgical margin. Amputated thumb need restoration as soon as possible by adequate reconstruction tool because of the relatively important function of thumb compared with other fingers. Throughout most of the 20th century, the standard surgical treatment of cutaneous melanoma was to radically excise the primary lesion with a 4-5 cm radical margin of surrounding skin. Recently a couple of randomized trials delineating what specific margin is safe have reported, and those studies showed local recurrence rates in patients having a 4-cm excision was no lower than those having a 2-cm excision in intermediate thickness melanomas. However, it has been unresolved yet about appropriate amputation level of thumb affected by melanoma. Level of amputation might effect on the selection of reconstructive methods. We present our 15 cases of melanoma of thumb and analyzed their Stage, surgical margin of skin and amputated level, reconstruction, and their prognosis. (Method) From 1979 to 2004, 15 patients received diagnoses of subungual melanoma of thumb. 2 patients had presented Stage 0 disease, 5 patients had presented Stage I disease, 4 patients had presented Stage II disease, and 4 patients had presented Stage III disease, No case had distant metastasis at first operation. Ulceration was presented in 12 cases. 8 patients had undergone lymph node dissection and in 4 of them regional metastases were found. Further retrospective analysis has focused on amputation level, surgical margin, and reconstruction methods. (Results) Operative therapy consisted of amputation. In 9 cases, thumb was amputated at 1st metacarpal bone, In 5 cases, thumb was amputated at IP joint or distal end of proximal phalanx. In one case of Stage 0, only the nail bed with periosteum at subungual was excised. More than 40mm radical margin of surrounding skin was acquired in 9 cases, and 30-15mm margin was performed in 4 cases, and 8-10mm was in 2 cases. Amputated thumb was reconstructed by pollicization in 8 cases, free toe to thumb in 2 cases, reverse forearm flap in 2 cases, local flap in 2 cases, and STSG in 1 case. No major complication of reconstructed thumb occurred. Local recurrence has occurred in 1 case in 10 mm margin case of Stage I disease. During following up period, 6 cases presented distant metastasis (5 lung, 1 liver ). 4 cases died by the metastasis disease within 34 to 60 months. All 4 cases in which the nodal status was proved to be negative pathologically by sentinel lymph node biopsy or ELND, survive with disease free. Five-year survival rate of 15 cases was 65.8%. In our cases, the survival rate in patients having a 1-3 cm excision was no lower than those having a 4-5 cm excision. The survival rate in patients amputated with the level of IP joint was no lower than those with the level of 1st metacarpal bone. (Conclusion) The pathological examination of axial lymph node is important to evaluate prognosis and make treatment plan. More than 10 years before, we performed ELND in the cases thickness more than 1.5mm. However, most cases has ulceration and measurement of thickness is sometimes difficult in subungual. Recently we perform sentinel lymph node biopsy and we can decrease lymphedema by selection the case that has the real indication of lymph dissection. We think the amputation level should be enough at IP joint in subungual melanoma such like our cases. 20mm of surgical margin of skin is enough, but 10mm margin has risk for recurrence even in thin melanoma. Narrow margin of excision might contribute to the increased choice of reconstructive tools, especially in local flaps and toe-to-thumb transfer.
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