Increased apoptosis coincides with onset of involution in infantile hemangioma

Objective: Hemangioma is an endothelial cell tumor that grows rapidly durin g infancy and regresses slowly during childhood. However, little is known a bout the natural history of this common tumor. To gain insight into the cel lular mechanisms that underlie, the switch from uncontrolled growth to invo lution of endothelium, rye investigated the extent of cellular apoptosis ve rsus proliferation in hemangioma specimens that spanned the natural life cy cle of the trumor. Methods: We analyzed apoptosis and cellular proliferation in frozen section s from 16 hemangioma specimens using the TUNEL assay to det ect apoptotic c ells and the Ki67 antigen to detect dividing cells. Results: Apoptosis was lon in proliferative phase hemangiomas but increased fivefold in involutive phase specimens obtained from children one to four years of age. Immunofluorescence double-labeling experiments showed that at least one third of the apoptotic cells were endothelial. As expected, cell ular proliferation was high in specimens up to 2 years of age but decreased significantly thereafter. Apoptosis was consistently low in nine normal sk in tissues (newborn to 4 years of age) obtained from discarded pathology sp ecimens. Conclusions: These results suggest that increased apoptosis during the seco nd year of life can offset cellular proliferation and may be involved in in itiating regression of hemangioma.