Mast cell tumor destruction by deionized water.

In a controlled study, malignant murine P815 mastocytoma cells exposed in vitro to distilled and deionized water died as a result of progressive swelling, degranulation, and membrane rupture. A 90% mean cell death occurred when cells obtained directly from culture were exposed to deionized water for 2 minutes. Of 6 cryopreserved malignant murine cell lines, which included Cloudman S91 melanoma, CMT-93 rectum carcinoma, MMT-06052 mammary carcinoma, and S-180 Sarcoma, only P815 mastocytoma and YAC-1 lymphoma were significantly (P less than 0.05) affected by hypotonic shock; Cloudman S91 melanoma cells were the most resistant. Mastocytoma cells were selectively killed by hypotonic solution, and lymphoma cells were also killed by isotonic saline solution. Local mast cell tumor (MCT) recurrence and percentage survival were evaluated in 12 cats (21 MCT) and 54 dogs (85 MCT) subjected to surgery alone or local infiltration of deionized water as an adjunct to surgery. Of all 16 incompletely excised MCT in cats, there was no local recurrence following injection. Four mast cell tumors (2 cats) regressed after being injected in situ. In dogs with clinical stage-I MCT, local recurrence was detected in 50% (5/10), but with injection after incomplete excision, local MCT recurrence was significantly (P less than 0.05) less (6.6%, 1/15). Percentage recurrence was significantly (P less than 0.05) less and survival significantly greater when incompletely excised grade-II MCT were injected. Mean follow-up period after surgery in cats and dogs was 35 and 23.4 months, respectively.