Autoimmune arthritis-related inflammation in the lungs is associated with a three-fold increase in the number of lung metastatic lesions in the SKG mice. Representative images of lungs from (a) Balb/c; (b) SKG; (c) SKG + Zymosan A; (d) Balb/c injected with TUBO cells; (e) SKG without Zymosan A + TUBO cells; (f) SKG + Zymosan A + TUBO cells (2/8 mice developed lung lesions); (g) Balb/c + 4T1 cells (3/11 mice developed lung lesions); (h) SKG without Zymosan A + 4T1 cells (8/8 mice developed severe lung metastasis); (i) SKG + Zymosan A + 4T1 cells (9/9 mice developed severe lung metastasis). (j) Percentage of mice that developed lung metastasis. (k and l) H&E of bone section showing high inflammation and image of lung with metastasis from the same 4T1-bearing SKG mouse. (m) A statistical analysis for correlation of bone inflammation and lung metastasis. The correlation coefficient for the 4T1 tumor-bearing SKG and SKG + Zymosan mice was determined to be 0.93 and 0.90. Correlation for TUBO-bearing mice was not calculated. (n to w) H&E staining of the lung sections from (n) SKG (moderate infiltration); (o) SKG + Zymosan A (moderate infiltration). (p) Balb/c + TUBO (no inflammation); (q) SKG + TUBO (moderate infiltration); (r) Balb/c + Zymosan A + TUBO; (s) SKG +Zymosan A + TUBO (moderate infiltration)(t) Balb/c + 4T1 (no infiltration); (u) SKG + 4T1 (severe infiltration); (v) Balb/c + Zymosan A + 4T1 (no infiltration); and (w) SKG + Zymosan A + 4T1 (severe infiltration). The solid filled arrow represents lung metastatic lesions, unfilled arrow represents neutrophils and unfilled circles represent macrophages. All images taken at 200 × magnification.