Our observations that the serum level of HSPA1A was lower in women with carcinoma in situ than in those with locally advanced invasive carcinomas and lower in well-differentiated slowly proliferating tumors than in more rapidly growing undifferentiated tumors are complementary to a prior analysis of intracellular HSPA1A levels in samples of breast cancer tissue28. Here, HSPA1A is linked to in situ carcinoma.