Pancreatic mucinous cystic neoplasm

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 Pancreatic mucinous cystic neoplasm

Pancreatic Mucinous Cystic Neoplasm (MCN) is a cystic epithelial neoplasm with malignant potential, primarily affecting women and typically arising in the body or tail of the pancreas. It is distinguished by mucin-producing columnar epithelium and a distinctive ovarian-type stroma.

1. Cause and Etiology

The precise cause of MCNs is not well understood, but the etiology is believed to involve a combination of genetic, hormonal, and environmental factors:

  • Hormonal influence: Strongly associated with female sex hormones—nearly all MCNs occur in women, especially in the perimenopausal age group (40–60 years). The ovarian-type stroma is often estrogen and progesterone-receptor-positive.
  • Genetic alterations:
    • KRAS mutations are commonly seen.
    • RNF43 mutations and SMAD4 or TP53 mutations may be present in more advanced or malignant cases.
    • No connection with familial pancreatic cancer syndromes is well established.

2. Pathophysiology

The pathophysiology of MCN involves:

  • Development of a mucin-producing epithelial lining, typically with a single layer of tall, columnar, mucinous cells.
  • Underlying dense ovarian-type stroma, which is a defining histologic feature.
  • Slow, progressive growth of the cystic lesion.
  • Potential for malignant transformation:
    • MCNs have a spectrum of dysplasia, from low-grade to high-grade.
    • Some develop into invasive mucinous adenocarcinoma.
  • MCNs are unilocular or multilocular cysts that do not communicate with the pancreatic duct (unlike IPMN).

3. Epidemiology

  • Sex: Over 95% occur in women.
  • Age: Most commonly diagnosed between 40 and 60 years.
  • Location: Predominantly in the body and tail of the pancreas.
  • Incidence: Rare, accounting for about 10–45% of resected pancreatic cystic neoplasms.
  • Prevalence increases with the widespread use of cross-sectional imaging.

4. Clinical Presentation

Most MCNs are asymptomatic and discovered incidentally on imaging. When symptomatic, patients may present with:

  • Abdominal pain or discomfort (vague, upper abdominal)
  • Palpable mass (rare)
  • Nausea or early satiety
  • Weight loss
  • Jaundice (rare, unless a tumor compresses the bile duct)
  • Symptoms of malignancy may appear late in the disease course

5. Imaging Features

Ultrasound:

  • Anechoic cystic lesion
  • May show septations or mural nodules

CT Scan:

  • Well-circumscribed unilocular or multilocular cystic mass
  • Thickened cyst walls or internal septations
  • Peripheral calcifications may be present
  • No communication with the pancreatic duct

MRI / MRCP:


  • T1 hypointense, T2 hyperintense
  • Better visualization of septations and mural nodules
  • No ductal communication, which helps differentiate from IPMN

Endoscopic Ultrasound (EUS):


  • Enables fine-needle aspiration (FNA)
  • Cyst fluid analysis:
    • High CEA levels (>192 ng/mL suggest a mucinous cyst.
    • Low amylase
    • Cytology may show mucinous epithelium or atypical cells

6. Treatment

Treatment depends on the size, presence of symptoms, and suspicion for malignancy.

Surgical Resection:

  • Mainstay of treatment, especially for:
    • Cysts >4 cm
    • Symptomatic lesions
    • Lesions with mural nodules or suspicious imaging features
  • Distal pancreatectomy (often with splenectomy) for lesions in the body/tail
  • Pancreatoduodenectomy (Whipple) if the lesion is in the head (rare)

Non-operative management:

  • Considered in selected cases:
    • Small (<3 cm), asymptomatic MCNs without high-risk features
    • Requires close radiologic surveillance

7. Prognosis

  • Excellent prognosis after complete resection of non-invasive MCN: >95% 5-year survival.
  • Malignant MCNs (those with invasive carcinoma) have a worse prognosis:
    • 5-year survival ranges from 20–60%, depending on stage and nodal involvement.
  • Prognostic factors:
    • Degree of dysplasia (low-grade vs. high-grade)
    • Invasion beyond the cyst wall
    • Presence of lymph node metastasis

References

1.       WHO Classification of Tumours of the Digestive System (5th ed., 2019)

2.       Tanaka M, et al. International consensus guidelines 2017 for the management of IPMN and MCN. Pancreatology. 2017.

3.       Reid MD, et al. Mucinous cystic neoplasms of the pancreas: review and update. Semin Diagn Pathol. 2014.

4.       Pitman MB, et al. Cyst fluid cytology and CEA analysis in the diagnosis of pancreatic cysts. Cancer Cytopathol. 2013.



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