An adult case of thrombocytopenia associated with posterior mediastinal hemangioma suggestive of Kasabach-Merritt phenomenon with uncertain diagnosis.

Mediastinal hemangiomas are rare, accounting for <0.5% of all mediastinal tumors. Kasabach-Merritt phenomenon, characterized by thrombocytopenia and platelet consumption associated with vascular tumors such as Kaposiform hemangioendothelioma and tufted angioma, is even rarer, especially in adults. Adult cases of Kasabach-Merritt phenomenon complicated by posterior mediastinal hemangioma are exceedingly uncommon and pose significant diagnostic challenges. This report describes the case of an adult with thrombocytopenia and posterior mediastinal hemangioma exhibiting features suggestive of Kasabach-Merritt phenomenon; however, a definitive diagnosis could not be established due to the absence of characteristic histological or molecular evidence of Kaposiform hemangioendothelioma or tufted angioma. The patient had been initially diagnosed with thrombocytopenia >10 years before admission, and during a routine physical examination, a posterior mediastinal mass was observed. The patient underwent successful surgical resection, and her platelet count normalized postoperatively; however, it remains uncertain whether this improvement was primarily due to the surgical removal of the lesion or perioperative transfusion support. Follow-up tests at 2, 4, and 8 weeks after discharge showed sustained normalization of platelet counts. This case highlights the diagnostic uncertainty in an adult patient suspected of having Kasabach-Merritt phenomenon and the treatment challenges involved in the management of mediastinal hemangiomas, underscoring the importance of diagnostic caution and clinical awareness necessary for distinguishing between conditions with similar presentations.