Based on a detailed clinical and laboratory investigation of 89 patients with histologically verified desmoid tumor and the pertinent medical literature, we have reviewed the etiologic factors, clinical characteristics, and results of treatment of this rare disorder. The incidence of the tumor in the Finnish population is low, 2.4 to 4.3 new cases per 10(6) inhabitants per year. The age distribution profile demonstrated four distinct peak periods: the juvenile period, the fertile period, the middle-age period and the old-age period. The juvenile desmoid tumor is an extraabdominal tumor found in young girls, the fertile variety is an abdominal tumor found in women, the middle age variety is also overwhelmingly abdominal but the sex ratio approaches equality, whereas in the old age group, both abdominal and extraabdominal tumors are equally frequent and the sex ratio is equal. In all male patients, the growth rate was low. A low growth rate was also recorded in young girls. A growth rate of twice that speed was seen in fertile women and four times that speed in the middle age group. In the old age group, a low growth rate, equal to that of male patients, was a rule. The fertile female patients with desmoid tumor had a significant predisposition to estrogen dominance and deviation from progesterone dominance. The direct relationship of the growth rate to the level of endogenous estrogen in the female patients and the demonstration of significant amounts of estradiol but not progesterone receptors in the tumor cytosol further suggest that the growth rate of desmoid tumor is regulated by steroid sex hormones. A significant number of patients with an abdominal desmoid tumor had a history of surgical trauma in the region of subsequent tumor growth. A very high number of the patients demonstrated multiple minor malformations of the bony skeleton. An increased frequency of these malformations was also recorded in the families of the patients and the distribution of the malformations among the family members was compatible with an autosomally dominant pattern of inheritance. After operation, the frequency of recurrence was not statistically different, regardless of whether the tumor was completely removed or not. A combination of operation and radiotherapy did not reduce the frequency of recurrences; in fact, it doubled it.(ABSTRACT TRUNCATED AT 400 WORDS)