Recent ultrastructural studies have shown that tubular carcinoma of the breast lacks basal lamina. This study was undertaken to determine the usefulness of light-microscopic examination of PAS staining for basal lamina in the differentiation of tubular carcinoma and sclerosing adenosis. Ten cases of tubular carcinoma show no basal lamina except for an occasional short segment. Ten cases of sclerosing adenosis show intact basal lamina except for short focal discontinuities. It is concluded that the lack of basal lamina in tubular carcinoma and its presence in sclerosing adenosis is a useful differential feature. Am J Surg Pathol 4: 75-77, 1980.