Supplementary Material for: Primary eosinophilic panniculitis of the greater omentum in a young girl: A case report

Background: Primary (or idiopathic) panniculitis involving the intra-abdominal adipose tissue is rare, and its pathogenesis remains unknown. A case of primary eosinophilic panniculitis that involved the greater omentum of a girl is reported. Case Presentation: The patient, an 11-year-old girl, complained of dull periumbilical pain and nausea, and radiological examination showed a mass lesion in the abdomino-pelvic cavity. On laparoscopy, a plaque-like, flat mass was seen in the greater omentum, and laparoscopic omental resection was performed. On histopathological examination, the interlobular fibrous septa of omental adipose tissue were widened by inflammatory edema, prominent infiltration of eosinophils, and loose proliferation of myofibroblasts. Dense lymphocytic infiltration was also noted around small veins. Inflammatory changes were mild in the fat lobules, and fat necrosis and infiltration of lipid-laden macrophages were absent. Findings of obliterative phlebitis or arteritis were not seen. Conclusion: Isolated involvement of the omentum by a panniculitic process is rare, and the pathogenesis of eosinophilic septal panniculitis found in the present case remains unknown, but involvement of a hypersensitivity reaction against some unknown stimuli is presumed, based on the histopathological resemblance of the omental lesions to erythema nodosum or eosinophilic panniculitis of the skin. We should keep in mind the possibility that the omental lesion in this patient is a harbinger of more serious immunological disorders. Careful, long-term follow-up and monitoring of the patient is needed.背景：累及腹腔内脂肪组织的原发性（特发性）脂膜炎（panniculitis）极为罕见，其发病机制迄今尚未阐明。本文报告1例累及大网膜（greater omentum）的原发性嗜酸性脂膜炎（eosinophilic panniculitis）病例，患者为女童。 病例介绍：患者为11岁女童，因脐周钝痛伴恶心就诊，影像学检查提示腹盆腔存在占位性病变。腹腔镜（laparoscopy）探查可见大网膜处存在斑块样扁平肿物，遂行腹腔镜下大网膜切除术。组织病理学检查显示：大网膜脂肪组织的小叶间隔纤维隔因炎性水肿增宽，可见嗜酸性粒细胞显著浸润，肌成纤维细胞（myofibroblasts）呈散在增殖；小静脉周围亦可见致密淋巴细胞浸润。脂肪小叶内炎性改变轻微，未发现脂肪坏死及载脂巨噬细胞浸润，亦未见闭塞性静脉炎（obliterative phlebitis）或动脉炎表现。 结论：以脂膜炎进程孤立累及大网膜的情况十分罕见，本次病例中发现的嗜酸性间隔性脂膜炎的发病机制仍不明确，但基于该网膜病变与皮肤结节性红斑（erythema nodosum）或皮肤嗜酸性脂膜炎的组织病理学相似性，推测其可能与针对某种未知刺激的超敏反应有关。需警惕该患者的网膜病变可能是更严重免疫性疾病的先兆，因此需对患者进行长期细致的随访监测。