In 7 out of 24 carcinoma-bearing animals we analyzed tumors taken from two different mammary glands of the same cat (named as a and b in Table 1); in this subgroup 4/7 tumors showed different score of CXCR4 expression among carcinomas derived from gland a and b from the same cat, possibly reflecting heterogeneity across tumour lesions. The gene discussed is CXCR4; the disease is neoplasm.