Abdominal Inflammatory Myofibroblastic Tumor
A 28-year-old woman was referred to our hospital because of abdominal pain and weight loss. During 4 weeks she had lost 15 kg in weight because of postprandial pain. She had pre-existent constipation, but no rectal bleeding, nor did she experience any night sweating. Physical examination did not show any anomalies except a left paraumbilical palpable mass. Ultrasound revealed a 6-cm hypoechogenic tumorous mass with sharp margins. A CT scan of the chest and abdomen showed an inhomogeneous round tumor of 73 × 61 mm with sharp margins and with hypodense fatty components in combination with enhancing soft tissue. The mass was located mesenterially, ventrally of the musculus iliopsoas with surrounding enlarged lymph nodes (maximum diameter 12 mm) (fig. ). Differential diagnoses like teratoma, liposarcoma or IMT were suggested. An additional PET scan revealed paratracheal lymph nodes which were interpreted as reactive, and the known left paraumbilical mass with only capsular FDG uptake. Ultrasound-guided biopsies were taken which revealed spindle cell proliferation with a mixed inflammatory cell infiltrate, in which immunohistochemical analysis showed positivity for vimentin, pankeratin (not uniform), and focally smooth muscle actin and calponin, suggesting an IMT.\nGiven the clinical presentation and the pathological findings, it was decided to perform an explorative laparotomy with total resection of the tumor. Macroscopic inspection showed a tumor with a diameter of 10 cm with a smooth capsular outer surface (fig. ). Due to locally aggressive growth, both a section of the colon and the jejunum had to be resected. Microscopy showed a mesenteric tumor comprising diffuse, not sharply delineated and unencapsulated spindle cell proliferation with lymph node involvement per continuitatem but without involvement of the colon or jejunum and without atypia. This spindle cell proliferation was accompanied by a cell-rich mixed inflammatory infiltrate with for instance many plasma cells, lymphocytes and eosinophilic granulocytes. The tumor contained centrally a large area of necrotic debris, maybe fat necrosis. Immunohistochemical analysis did not reveal signs of a specific spindle cell tumor, carcinoma or malignant lymphoma (fig. ). The diagnosis was IMT (differential diagnosis: primary fat necrosis surrounded by a pseudocapsule of extensive reactive fibrosis with organization). The postoperative period was uncomplicated and the patient could be discharged from the hospital after 4 days.