Mucinous adenocarcinoma of the appendix

Mucinous adenocarcinomas of the appendix are at the malignant end of the spectrum of the mucinous neoplasms that affect the caecal appendix. 

For the mucinous carcinomas involving the remainder of the colon, please refer to the article on mucinous carcinoma of the colon.

Epidemiology

The peak incidence is in the 6^th and 7^th decades ^1,3. Associations with other colonic neoplasms and chronic ulcerative colitis have been reported ¹. 

Clinical presentation

Symptoms are much more likely to manifest than in the other more indolent appendiceal neoplasms (e.g. adenoma or neuroendocrine tumours). The spectrum of symptoms varies from vague abdominal pain, nausea, vomiting, and weight loss, to a palpable mass, abdominal distension, and acute appendicitis ^1,3.

Pathology

Considerable controversy still exists regarding mucinous neoplasms of the appendix pathologic classification and nomenclature ¹. According to a panel of specialist review in 2016, a new nomenclature and classification for the appendiceal mucinous neoplasms based on their histologic type and biologic behaviour has been proposed and since then the term mucinous adenocarcinoma should be reserved for those mucinous tumours with infiltrative invasion beyond the muscularis mucosa ^1,2. 

An adenocarcinoma is defined as mucinous when extracellular mucin corresponds to more than 50% of the lesion. The signet ring cell carcinoma variant occurs when a tumour has more than 50% of cells showing the classical signet ring morphology ^1,2.  

Radiographic features

Fluoroscopy

Barium enema 

Non-specific signs may indicate a tumoural lesion adjacent to the caecum, including the non-filling of the appendix, a submucosal mass lesion at the caecal pole, and an extraluminal compression of the caecum ¹.

Treatment and prognosis 

Staging and management of these are different from those of colorectal carcinoma, please refer to the appendiceal mucinous neoplasms TNM staging for further details.