[On parosteal lipomas of the limbs].

Among the benign neoplasias of mesenchymal origin, parosteal lipomas represent a relatively rare occurrence. They are deep seated (subfascial) lipomas which during the course of their slow growth become adherent to the periosteum. The parosteal lipoma is not dissimilar to the so-called common or superficial lipoma both in terms of its macroscopic appearance, since this neoplasia has no capsule which separates it from surrounding tissue and likewise enables an easy enucleation owing to the presence of a cleavage plane, and in terms of its microscopic appearance since it is made up of mature adipose cells. Moreover, comparative cytogenic tests have revealed chromosomic alterations common to both the superficial and parosteal lipoma. The peculiarity of the parosteal lipoma lies in its clinical evolution which depends on the original site; it is in fact most often described in relation to bone segments of the limbs where it may lead to the compression of the vasculonervous axes. In particular, parosteal lipoma of the forearm, especially if localised in the upper third, represents a separate clinical entity given that, during the course of its growth, it may cause the compression of the posterior interosseous nerve and the surface (sensitive) branch of the radial nerve. This occurrence, which is observed in approximately half of all cases, must be taken into consideration and should lead to the decision to operate in order to prevent compressive sequelae involving nervous axes. After reviewing the literature on the subject, the authors report their experience of four recent cases and evaluate the anatomical, clinical, diagnostic and therapeutic aspects of parosteal lipoma.