This is also consistent with a significant correlation between breakthrough pain, measured by pain questionnaire, and combined high serum levels of BDNF and IL6 in patients with BM, and also by immunofluorescence staining showing IL8 expression that was more in mesenchymal stromal cells rather than in tumors cells, and close to LAMP-2 positive acidifying carcinoma cells in BM tissue sections. Here, BDNF is linked to carcinoma.