[Benign mesothelioma of the uterus. Clinical and histopathological aspects and evidence of its mesothelial origin. Apropos of 1 case]. / Le mésothéliome bénin de l'utérus. Aspects cliniques, histopathologiques et évidences de son origine mésothéliale. A propos d'un cas.

Benign mesothelioma is a rare tumor nearly always find in relation to the genital tract. We report the case of a 47-year, old woman admit in the gynecologic department for metrorragia. The tumor was composed of irregular tubules between smooth muscle cells, lined by flattened or cuboidal cells without nuclear atypia or mitoses. The tumor cells express cytokeratins and vimentin. Histologically, differential diagnosis can be made with adenocarcinoma or vascular proliferation like lymphangioma, hemangioma or angiomyoma. Clinical outcome is always favourable without recurrence or malignant transformation.

MLH1 and MSH2 protein immunohistochemistry is useful for detection of hereditary non-polyposis colorectal cancer in young patients.

AIMS: Hereditary non-polyposis colorectal cancer is related to germline mutations of DNA mismatch repair genes MLH1 and MSH2, which result in microsatellite instability and loss of protein expression of the corresponding mutated gene in the tumour tissue. METHODS AND RESULTS: MLH1 and MSH2 protein expression was studied by immunohistochemistry in paraffin-embedded surgical samples of 100 colorectal adenocarcinomas occurring before 50 years of age. Absence of tumour cell nuclear staining with positive internal control (normal mucosa, lymphoid follicles) was considered negative. Loss of MLH1 or MSH2 expression was found in 20 cases with microsatellite instability in 15 cases. Twelve of these patients had a family history of colorectal cancer. Compared with MLH1- and MSH2-positive cases, MLH1- or MSH2-deficient colorectal adenocarcinomas were significantly associated on multivariate analysis with a younger age (38 vs. 43 years, P;0.0224), a larger tumour size (60 +/- 6 vs. 46 +/- 2 mm, P=0.0291), an expanding margin (85% vs. 51%, P=0.0159), a higher number of tumour-infiltrating lymphocytes assessed by CD3 immunostaining (202 +/- 48 vs. 33 +/- 4 CD3+ lymphocytes/10 high-power fields, P=0.0039), and a grade 2 Crohn's like lymphoid reaction (70% vs. 9%, P=0.0037). The two groups were not different for tumour site, differentiation, pTNM stage, vascular and perineural invasion, peripheral adenomatous residue, and 5-year survival rates. CONCLUSIONS: MLH1- or MSH2-deficient colorectal carcinomas of young patients exhibit pathological and molecular features similar to hereditary non-polyposis colorectal cancer. This suggests that MLH1 and MSH2 immunohistochemistry is valuable for detecting hereditary non-polyposis colorectal cancer in young patients.