[Extra-abdominal desmoid tumor. Microscopic aspects and histogenesis].

Extra-abdominal desmoid is an unusual and underreported tumour in dermatological literature. We report a new case of such a lesion which was subjected to light, electron-microscopic and immunohistochemical studies. The results showed that proliferating cells exhibit features of myofibroblasts, both at the ultrastructural study (presence of cytoplasmic myofilaments) and the immunohistochemical study (cytoplasmic expression of vimentin and muscle-specific actin). Since these findings strongly suggest that desmoid tumour originates from myofibroblasts the term (extra-abdominal) "myofibroblastoma" could be proposed.