Pancreatic PEComa

Pancreatic perivascular epithelioid cell tumours (or "Pancreatic PEComas") are a subtype of the larger family of PEComas. Pancreatic PEComas are very rare with <20 cases described.

Clinical presentation

More common in adults (in contrast to lymphangiomas in the head and neck, which are more common in children). Account for approximately 1% of abdominal lymphangiomas. More common in women

Pathology

As their name suggests, these tumours arise from perivascular epithelioid cells and occur due to a genetic alteration in the tuberous sclerosis gene complex. The PEComas are a group of tumours, including

• clear cell "sugar" tumours
• angiomyolipoma
• lymphangiomyomatosis

The cells are periodic acid-Schiff stain (PAS) positive and diastases sensitive. Immunohistochemistry markers include: smooth muscle and melanocytic markers (SMA, HMB-45, and HMSA-1) ^2-3

Radiographic features

CT

• tend to occur in the head and body of the pancreas
• well-demarcated
• hypoenhancing mass with a hypervascular capsule
• may demonstrate hemorrhage or cystic degeneration
• fat attenuation may be present

MRI

Signal characteristics include

• T1: hypointense
• T2: hyperintense
• T1 C+: heterogeneous enhancement
• T1 FS: macroscopic fat intensity may be present (saturates on a fat sat sequence)

Ultrasound

• nonspecific pancreatic mass
• heterogeneous echogenicity
• well-encapsulated

Treatment and prognosis

Given the rarity of the lesion, there is no standard treatment

Differential diagnosis

​A pancreatic PEComa should only be considered if a pancreatic mass is well-encapsulated, but since it is so rare, it should never be at the top of a differential. It's probably only reasonably suggested in a patient with tuberous sclerosis and a pancreatic mass.

Other similar pancreatic masses that should be considered before it are

• pancreatic endocrine tumour ("islet cell" tumor)
• solid-pseudopapillary tumour (SPT)
• metastasis to the pancreas
  • also rare, but much more likely than a pancreatic PEComa