Enlarging cystic lymphangioma of the mediastinum in an adult: is this a neoplastic lesion related to the recently discovered PIK3CA mutation?

Cystic lymphangioma, a lymphatic system malformation, is usually observed in infants and children and is rarely found in adults. It most commonly occurs in the cervicofacial region, followed by the axilla. Mediastinal cystic lymphangioma is rare, accounting for 1.8% of all mediastinal cysts. Herein, we present an exceedingly rare adult case of mediastinal cystic lymphangioma that had increased in size over a 5-year period. Although fluid collection might be an alternative explanation for this increase in size, this lymphangioma might harbor a neoplastic nature related to the recently discovered PIK3CA mutation.

Immune response: A possible role in the pathophysiology of hemangioma.

Hemangioma is a distinct category of benign vascular tumors characterized by presentation within the first weeks of life, rapid growth during the first year and variable degree of spontaneous involution over a period of several years. Recent research reported that CD8+ T cells in hemangiomas, and the endothelia of hemangioma uniquely expressed leukocyte marker FCgammaRII and myeloid cell marker. Presence of high levels of indoleamine 2,3-dioxygenase in proliferating hemangiomas and significantly decreasing during involution was also confirmed. Topical application of imiquimod cream, an immune regulator, to proliferating hemangiomas apparently accelerated regression of the lesions. These findings suggest immune response may be involved in the pathogenesis of hemangioma. The endothelia of hemangioma may express various markers to escape the immune surveillance. An immune response may be one of the mechanisms for hemangioma regression. Strategies with systemically or locally applying immune regulator into the tumor may be an applicable way in accelerating the involution of hemangioma.