Fibronectin-containing hyaline globules in malignant melanoma.

Hyaline globular inclusions were found in a case of malignant melanoma. The globules were both intracellular and extracellular in the primary neoplasm and in metastases to lymph nodes, liver, and lung. They were studied immunohistochemically and were found to contain fibronectin, a glycoprotein of high molecular weight. Ultrastructurally, the globules were composed of electron-dense, finely fibrillar aggregates. It is suggested that the neoplastic cells produced the fibronectin, which accumulated in globular form. Ten additional cases of malignant melanoma were studied; none of these had hyaline globules or intracellular globular fibronectin. The globules were compared to similar structures described in Spitz's nevi and other neoplasms. Immunohistochemical analysis was most useful in distinguishing the globules found in the malignant melanoma from those found in other conditions.