[The margin of safety and depth of excision in surgical treatment of basalioma. Use of 3-dimensional histologic study of 2,016 tumors].

During the treatment of 2016 basal cell carcinomas (BCC), 1757 of which were primary tumours and 259, recurrences, every operation was followed by a check on radicality by means of histological evaluation of the margins of the excised tissue (three-dimensional histology). The average safe margin at first excision was 3.8 mm, and excision normally extended to the lower subcuticular border in depth. After first excisions, tumour tissue was found in 31.6% of histological sections prepared from the marginal sections at the circumference and/or on the underside of the excised material. Tumour material was far more frequent in the marginal area (28.3%) than on the underside (7%). With a 2-mm safe margin around the primary BCC there were still 46.7% tumour-positive marginal sections; with 4 mm, 20.3%; and with 6-8 mm, 14.7%. Fibrosing BCC and tumours with diameters over 20 mm, and recurrent BCC in particular had a significantly larger share of tumour-positive marginal sections and considerably more frequently required two or more reoperations until the final radical excision than did the solid and superficial types of BCC. An average safe margin of 4.5 mm plus standard deviation to give 7 mm (standard deviation 2.5 mm) was necessary for radical excision of primary BCC, but often even larger margins, up to a maximum of 3.2 mm were necessary. Hence, when surgical treatment of BCC does not include three-dimensional histological evaluation generous safe margins are necessary. Surgery with histological monitoring is the only justifiable method of treating tumours of the fibrosing type, recurrent BCC and BCC over 10 mm in diameter.(ABSTRACT TRUNCATED AT 250 WORDS)