Pancreatic Pathology Online

Pathology of Mucinous Cystic Tumours of the Pancreas  

Dr Sampurna Roy MD           

 

The classification of these tumours has been the subject of much debate.

Mucinous cystic tumours are :

- Benign mucinous cystadenomas: Single epithelial layer of non-dysplastic  mucin secreting cells.

- Borderline mucinous cystic tumours: Non-invasive proliferative  mucinous (or borderline) lesions, where there is epithelial dysplasia but no evidence of invasion, and

- Mucinous cystadenocarcinoma:

There is obvious invasion.

The great majority of these relatively rare tumours occur almost  exclusively in women (mostly middle-aged).

They are found most frequently in the body and tail of pancreas and are therefore quite easily removed by a distal pancreatectomy.

Most patients commonly presents as a slowly enlarging abdominal mass. Patients with malignant tumours may have weakness, anorexia and weight loss.

Gross features:  

The tumour is well circumscribed, encapsulated, unilocular or multiloculated and 2 to 20 cm in diameter.

Inner surfaces of the cysts are smooth or show papillary projections, particularly in malignant types.

The contents of the cyst are mucoid with occasional hemorrhage.

The cysts do not communicate with the duct system.

The tumours, which is usually multicystic, should be well sampled histologicaly (at least one block per cm of maximum diameter of  tumour) in order that the presence of dysplasia in the lining epithelium or invasive malignancy can be assessed.

Microscopic features:

The cysts are lined by PAS-positive, mucus-secreting columnar epithelial cells, occasionally with some endocrine, Paneth and/or goblet-like cells. Glycogen is absent.

Cell stratification, papilla or gland formation and crypt invagination may be seen.

Beneath the epithelium is a densely cellular fibrous ("ovarian-like")  stroma. 

At the benign end of the spectrum of appearances the cystic spaces are lined by a single layer of mucin secreting epithelial cells. 

Borderline cases show moderate dysplasia such as papillary infolding, cellular pseudostratification. 

Mucinous cystadenocarcinomas show atypical epithelium, often with hemorrhage, calcification or chronic inflammation in the cyst wall.

Rarely sarcomatous areas are seen.

The tumours may be invasive or non-invasive.

Areas of dysplasia are found in a significant number of cases.

The pathologist must carefully look for the presence of any invasive malignancy.

The tumours should be completely excised and studied extensively for the presence of invasion, and when absent the patient should be reassured.

Pitfall:

Often there are areas of necrosis within the tumour and there may be loss of epithelium from the cyst wall with associated inflammation, sometimes accompanied by foreign body giant cells.

Biopsy of such an area can lead to an erroneous diagnosis of pancreatic pseudocyst complicating pancreatitis.

The presence of any lining epithelium or the characteristic  ovarian like stroma, as well as the clinical picture should help avoid this well known pitfall.

Prognosis:

- Majority of the patients (benign, borderline and malignant but non-invasive) are cured by complete excision.

- Prognosis of mucinous cystadenocarcinoma depends on the extent of the tumour invasion.

Immunohistochemistry:

Most cases show immunoreactivity for epithelial antigens (cytokeratins 7, 8, 18 and 19 and EMA) and CEA.

Some show positive reaction for:

- Endocrine cells (serotonin) ;

- Mesenchymal markers (vimentin, smooth muscle actin) in pseudosarcomatous or sarcomatous areas and

- Estrogen and progesterone receptors marker (in stromal cells).

Ultrastructural features:

Columnar cells show apical microvilli and mucin vacuoles.

Differential diagnosis:

- Intraductal Papillary Mucinous Tumours

- Solid Pseudopapillary Tumours  :

- Acinar cell cystadenocarcinoma :

- Cystic endocrine tumour : Neoplasms of the Endocrine Tumours :

- Benign lymphoepithelial cyst :

- Pseudocysts : No epithelial lining ; associated with chronic pancreatitis ; male preponderance.

 

Further reading:

PIK3CA mutations in mucinous cystic neoplasms of the pancreas.

Low interobserver agreement in cytology grading of mucinous pancreatic neoplasms.

MicroRNA‑224 is downregulated in mucinous cystic neoplasms of the pancreas and may regulate tumorigenesis by targeting Jagged1.

Mucinous cystic neoplasms of the pancreas: are we overestimating malignant potential?

Clinicopathological and CT features of mucinous cystic neoplasms of the pancreas.

Mucinous cystic neoplasms of the pancreas: pathology and molecular genetics.

Mucinous cystic neoplasms of the pancreas.

From the Archives of the AFIP. Mucinous cystic neoplasms of the pancreas: radiologic-pathologic correlation.

 

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

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