BACKGROUND: Leiomyosarcoma is a rare malignant tumor of smooth muscle origin and represents 10-20% of all soft tissue sarcomas. Primary colon and rectal sarcomas constitute < 0.1% of all large bowel malignancies. In Li-Fraumeni syndrome, sarcomas are the second most frequent cancer (25%). Li-Fraumeni syndrome is a genetic disease with a familial predisposition to multiple malignant neoplasms. This syndrome has an autosomal dominant pattern of inheritance and high penetrance characterized by germline TP53 mutations. Patients with a history of cancer who do not meet all the \"classic\" criteria for Li-Fraumeni syndrome are considered to have Li-Fraumeni-like syndrome. To the best of our knowledge, this article is the first report of a patient with rectal leiomyosarcoma as the initial phenotypic manifestation of Li-Fraumeni-like syndrome. The authors also present a literature review.
METHODS: A 67-year-old Brazilian woman underwent anterior rectosigmoidectomy and panhysterectomy secondary to rectal leiomyosarcoma. She subsequently developed carcinomatosis and died 2 years after the operation. Her family medical history consisted of a daughter who died at 32 years of age from breast cancer, a granddaughter diagnosed with adrenocortical carcinoma at 6 years of age and two siblings who died from prostate cancer. A genetic study was carried out to identify a pathogenic variant of Li-Fraumeni syndrome. In the DNA extracted from the peripheral blood leukocyte, restriction fragment length polymorphism was analyzed to search for mutations in the TP53 gene. The DNA sequencing identified the germline pathogenic variant p. R337H heterozygous in exon 10 of TP53. The patient was classified as having Li-Fraumeni-like syndrome.
CONCLUSIONS: In patients with rectal leiomyosarcoma, it is advisable to investigate the family history of cancer and perform genetic studies to screen for Li-Fraumeni syndrome.

Li-Fraumeni syndrome (LFS) is a cancer-prone, autosomal dominant syndrome caused by underlying germline gene mutations of TP53, a tumor-suppressor gene encoding the p53 protein with a major role in apoptosis, DNA repair and cell cycle regulation. Cumulative cancer incidence for LFS patients by the age of 70 years is 80-100%, mostly involving adrenocortical carcinoma, brain tumors, bone and soft tissue sarcomas, leukemia and female breast cancer from the age of 20 years. Dominant negative TP53 variant is correlated with an increased tumorigenesis risk in LFS. Sporadic TP53 mutations are related to almost half of global cancers since p53 in addition to p73 protein represent essential players in anticancer cellular protection. Epidemiological aspects concerning skin cancers, especially malignant melanoma (MM), in LFS are less clear. A low level of statistical evidence demonstrates LFS cases with pediatric MM, multiple MM, spitzoid MM, atypical presentations, mucosal and uveal MM. Retrospective cohorts indicate a higher cumulative risk than the general population by the age of 70 years for MM and basal cell carcinoma. Non-syndromic and syndromic TP53 mutations are a major pathway of metastasis, including MM. In LHS, an important level of awareness involves skin cancers despite not being a part of the typical malignancy-containing picture. Additional data are crucially needed. However, at least one dermatologic control is a step in the multidisciplinary panel of surveillance of these patients; but in cases with benign and pre-malign pigmentations, serial dermatoscopy and full body photography are recommended for early melanoma detection in order to improve the prognosis and to reduce the overall malignancy burden.