Multinucleated stromal cells of the anal mucosa: a common finding

Aims: To document the presence, morphology, immunophenotype and ultrastruct ure of multinucleated stromal cells within the anal mucosa and to discuss p ossible pathogenetic mechanisms for this occurrence. Methods and results: Multiple sections of normal anal mucosa from 30 abdomi noperineal resection specimens were analysed by light microscopic, electron microscopic and immunohistochemical methods. Multinucleated stromal cells were found in 22 cases (73%). They contained two to five nuclei, arranged i n a linear fashion or in a rosette or grape-like pattern. They stained posi tive for vimentin and negative for actin, desmin and oestrogen/progesterone receptors. Ultrastructural examination confirmed their fibroblastic lineag e. Mast cells were frequently observed in the immediate vicinity of mono- a nd multinucleated cells. Conclusions: Multinucleated stromal cells are a common occurrence in the no rmal anal mucosa. They should not be misinterpreted as neoplastic cells. Ma st cells may play a role in their morphogenesis.