Subcutaneous myxoid liposarcoma (ML) is exceedingly rare, with only two or three cases having been reported. Lipoblastoma (LB), a rare fatty tumor that arises in infants and children, is unknown after adolescence. In contrast to ML, LB is often superficial. The two tumors can be difficult to distinguish due to many histologic similarities. We examined a 0.9 cm superficial subcutaneous nodule from the dorsal neck of a 48 year old man that had been growing slowly. Three and one half years later, a 0.4 cm palpable recurrent nodule was excised from the scar. The patient is now free of disease at 7.5 years. Because of these unusual features, we performed clinicopathologic, immunohistochemical and molecular analysis of this unusual tumor to decide if this represented a rare cutaneous ML or an unprecedented example of LB in an adult. The primary featured a thick fibrous pseudocapsule with foci of lymphocytes and infiltrating nests of semi-mature fetal-appearing adipocytic tissue. This surrounded a more immature cellular-but-cytologically-bland myxoid tissue featuring stellate cells and signet lipoblasts. There were fibrous sep at the periphery and the vasculature was rather inconspicuous. The 0.4 cm diameter recurrence was distinctly lobular and had minute satellite nodules. It was composed of uniform fetal-appearing bland myxoid lipoblastic tissue featuring signet ring lipoblasts surrounded by a few spindle cells. In both tumors, lipoblasts expressed S-100 protein. In the primary, 5

作者：J S, Silverman；J, Hamilton；A, Tamsen

来源：Pathology, research and practice 1999 年 195卷 11期