Background
The retroperitoneum (RP) may be affected by variety of infectious,
inflammations, rare benign tumors or malignant neoplasms that can be
either primary or metastatic. Malignant tumors of the retroperitoneum
happen four times more often than benign lesions.(1, 2)
Benign retroperitoneal tumors (RPT) are usually detected clinically and
the most common one is neurogenic tumors (30%), followed by teratomas
(15%).
Malignant RPTs are very rare tumor, count 0.1-0.2 % of all malignant
tumors. Most of them are primary tumors, in them the most common type is
retroperitoneal but metastatic tumors may involve retroperitoneum. (3,
4). Metastatic RPTs may originate from kidney , bladder or genitalia.(5)
Invasion of malignant tumors to the retroperitoneal is very rare and
usually has been reported as an unusual presentation of gastrointestinal
stromal tumors (GISTs).(6, 7)
On the other hand, appendiceal tumors are rare and usually manifest as
appendicitis. Most are harmless and can be handled with appendectomy.(8)
The WHO classifies three subtypes of
mucinous appendiceal neoplasms; mucinous adenoma, low-grade appendiceal
mucinous neoplasm (LAMN), and mucinous adenocarcinoma (9)
In this case report we present a novel case of an appendix tumor which
manifested with retroperitoneal mass by invasion from peritoneal cavity.