Possible mechanism for the homing of the inoculated TK-gene modified tumour cells onto the tumour site include: (1) association of tumour cells more readily with tumour cells than with other non-malignant cells, (2) presence of tumour produced chemotactic factors [27–31] that attract other tumour cells and (3) in situ IP tumour masses may be devoid of a “repellent” mesothelial lining, thus allowing adherence of other cells [23]. Here, TKT is linked to neoplasm.