Osteonectin expression correlates with clinical outcome in thin cutaneous malignant melanomas

Osteonectin, also termed BM40 or SPARC (secreted protein, acidic and rich i n cysteine) is a multifunctional glycoprotein involved in tissue mineraliza tion, cell-extracellular matrix interactions as well as angiogenesis. It ha s been suggested that osteonectin may play a key role in the process of tum oral invasion and metastasis in certain malignancies. In this study, we rev iewed the clinical records and the histopathologic slides of 188 thin cutan eous malignant melanomas (less than or equal to 0.75 mm). Among them, 12 ca ses underwent progression and were selected for the study. Osteonectin expr ession was investigated by immunohistochemistry in these 12 patients and 24 matched controls who did not undergo progression. Osteonectin staining was correlated with clinical outcome and other clinicopathologic parameters. p rogression-free and disease-specific survival rates were calculated dth the Kaplan-Meier method and their differences were evaluated by the log rank t est. Overall, immunoreactivity for osteonectin was found in 23 (63.8%) case s. Eighteen cases (50%) displayed staining in 1% to 50% of neoplastic cells whereas five cases (13.8%) showed a diffuse positivity in more than 50% of the tumor cells. Osteonectin expression was significantly correlated with risk of progression (P = .01), incidence of distant metastases (P = .005) a nd survival (P = .03). There was a higher incidence of osteonectin-positive tumors in cases that did experience regional lymph node metastases versus those cases that did not, but that difference did not reach statistical sig nificance (P = .06). No significant:correlation was found between osteonect in expression and other clinicopathologic features, including age, sex, sit e, histotype, Clark's level, presence of regression, presence of inflammato ry response, and tumor growth phase. Our data showed that osteonectin expre ssion is a predictor of clinical outcome in thin cutaneous melanomas. HUM P ATHOL 30:339-344. Copyright (C) 1999 by W.B. Saunders Company.