Residual lesions after Kasabach-Merritt phenomenon in 41 patients

Background: Kasabach-Merritt phenomenon (KMP) is the association of a vascu lar tumor and thrombocytopenic coagulopathy. Vascular tumors are either kap osiform hemangioendothelioma or tufted angioma but not "true" common hemang ioma of infancy. There is a conspicuous absence in the literature regarding the late outcome and possible residual lesions after apparent clinical cur e of KMP. Objective: The purpose of the study was to analyze these residua in a large number of patients. Methods: Clinical data on 41 patients who had KMP were accrued in an intern ational cooperative study. The emphasis was on the residual lesions after r esolution of the thrombocytopenia and other coagulation abnormalities. Imag ing studies (follow-up magnetic resonance imaging studies available for 10 patients) and histologic specimens (30 specimens available for 26 patients, 18 biopsies done during the KMP and 12 concerning the sequelae) were revie wed. Results: Residual lesions after "cure" of KMP were common. They exhibited 3 clinical patterns: type I lesions (n = 28) showed a cutaneous red stain, w ith or without associated red papules. The stain might overlap a minor fibr otic infiltration or a significant poorly delineated diffuse fibrotic infil tration. These cutaneous vascular lesions varied in size and appearance ove r time and were occasionally painful. Type II lesions were telangiectatic s treaks and swelling (n = 5), and type III lesions showed a minor, firm, irr egular, subcutaneous mass assessed by palpation or deep infiltration eviden ced by computed tomography or magnetic resonance imaging (n = 8). A fourth feature was sequelae in muscles and/or joints. Histologically, tufted angio ma was more common in the specimens from residual lesions, whereas kaposifo rm hemangioendothelioma was more common during the active phase of KMP. Ima ging findings were remarkably reproducible and revealed a persistent vascul ar tumor. Conclusion: Residua of tumors associated with KMP are common after the reso lution of thrombocytopenia and coagulopathy. They are (more or less) promin ent dormant vascular tumors, not "scars" and, clinically as well as histolo gically, they differ markedly from involuted hemangioma.