Distinctive imaging patterns such as "whorled appearance" in desmoid tumors, mucinous ascites, hypervascularity in neuroendocrine tumors help narrow the differential diagnosis; however some lesions present overlapping features, making the differential diagnosis more challenging. Recognition of subtle radiological signs, such as calcifications or necrosis could help differentiating lesions.

MISTY MESENTERY

This term describes increased mesenteric fat attenuation that could represent fat infiltration by inflammatory cells, fluid, tumor, and/or fibrosis [1].

It is a non specifical sign, linked to numerous conditions, that’s why becomes important to know the whole clinical picture of the patient, such as other pathologies in the abdomen (or pelvis), laboratory findings, symptoms etc.

Fig 1: Idiophatic Misty Mesentery. 45 yo man without symptoms CT shows increased mesenteric fat attenuation.

Fig 2: SMV thrombosis in a 75 yo patient with increased mesenteric fat attenuation.

SOLID LESIONS

• Desmoid Tumor

Are uncommon, benign, non-inflammatory fibroblastic neoplasms that can occur anywhere in the abdomen, abdominal wall, or extra-abdominal tissue , locally aggressive [2,3]. Mesentery often shows "whorled appearance"[2]. Compression or invasion of adjacent structures can occur as the tumor grows. 

Fig 3: Desmoid tumor. A soft tissue density mass was detected in a 60 yo patient, it grows in the mesenteric fat, causing compression of the right ureter.

• NET (Carcinoid)

This tumor represent the most common malignant neoplasm of the small bowel, especially the distal ileum [4]. Mesentery is involved in 80% of the patient, since is not easy to find the primary lesion (wich is often too small to observe) sometimes a mesenteric mass is detected first [1], calcifications may be visible on CT in up to 70% of cases [2]. 

Fig 4: NET. Mesentery mass detected in a 55 yo patient. A soft tissue density mass partially calcified with desmoplastic reaction tethering bowel and vasculature wich leads to vascular sufference of the intestinal loops .

CYSTIC LESIONS

• Pseudomixoma-peritonei

Refers to a syndrome of progressive intraperitoneal accumulation of mucinous ascites related to a mucin-producing neoplasm, also known as jelly belly. It is most commonly caused by a mucinous tumor of the appendix, but also ovarian or pancreatic tumors. It often shows:

1. simple or loculated low attenuation fluid throughout intraperitoneal spaces, omentum, and mesentery; 
2. scalloping of visceral surfaces, particularly the liver [5].

Fig 5: Pseudomixoma peritonei. Mucinous ascites detected in a 90 yo woman. Primary tumor was detected in the appendix.

LYMPHOMA

Is the most common malignant neoplasm of the mesentery, and 30–50% of mesenteric lymphomas are non-Hodgkin type disease [6]. It shows generally with multiple round, mildly homogeneously enhancing masses. Conglomerated lymphadenopathy on both sides of the mesenteric vessels without significant vessel caliber change and with an intact perivascular fat border is called “sandwich sign [2].

Fig 6: Lymphoma. Multiple masses detected in a 65 yo man. Sandwich sign.

INTRAPERITONEAL SEEDING

The peritoneum is a common site of metastasis, especially from malignancies originating in the abdomen and pelvis. Presence of peritoneal carcinomatosis indicates a poor prognosis [7]. Ascites may be present as well. Typical peritoneal thickening "omental cake" like, refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake [8]. 

Fig 7: Intraperitoneal seeding. Typical peritoneal thickening "omental cake" like refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake.

Fig 8: Intraperitoneal seeding. Malignant ascitis.