{'fraction_non_alphanumeric': 0.027848101265822784, 'fraction_numerical': 0.004430379746835443, 'mean_word_length': 5.533057851239669, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Papillary endothelial hyperplasia in a bone marrow transplant recipient with extensive chronic graft‐versus‐host disease

A 16-year-old male bone marrow transplant (BMT) recipient with extensive chronic graft-versus-host disease (GVHD) noticed a small tender mass (30 mm · 20 mm) in the right thigh with subcutaneous bleeding (top). He had been transplanted with bone marrow from a human leucocyte antigen (HLA)-identical sister 3 years earlier for severe aplastic anaemia. Because pancytopenia with mixed chimaeric status had recurred several months after the transplant procedure, the patient had been administered a peripheral blood stem cell transplant from the same donor without conditioning. Thereafter, he had suffered from extensive chronic GVHD in the skin, liver, oral mucosa, eyes and gut. When the mass was noted, he was receiving intensive immunosuppressive therapy. The pathological examination of the excised mass revealed an organizing thrombus in a vessel with intravascular papillary endothelial hyperplasia (IPEH, bottom left). A high-power view showed numerous tuft-like proliferations of endothelial cells devoid of pleomorphism and mitotic activity (bottom right). IPEH, rare in young patients, is a benign lesion of the vascular system caused by excessive proliferation of endothelial cells in normal or deformed vessels and represents an unusual form of organizing thrombus. As the histological features of IPEH mimic those of angiosarcoma, consideration of clinical and histological features is important to avoid over-treatment of this benign condition.