In contrast, no or low-frequency IgM was found in neoplastic mesenchymal cells (1 of 47, [2.1%]; including lipoma, fibroma, and leiomyoma cells [Figure 1I]) and in normal mesenchymal cells (1 of 34, [2.9%]; including lipocytes, fibroblasts, and smooth muscle cells). The gene discussed is CD40LG; the disease is lipoma.