Table 2 Radiological and pathological characteristics of pseudo-IPMNs.

From: Pancreatic ductal adenocarcinomas associated with intraductal papillary mucinous neoplasms (IPMNs) versus pseudo-IPMNs: relative frequency, clinicopathologic characteristics and differential diagnosis

 

Retention Cyst (secondary duct ectasia)

Large-duct-type PDAC

Simple mucinous cyst

Congenital cyst

Paraduodenal wall cyst of PDP

Pseudocyst of conventional type

Necrosis within the tumor

Distribution, body/tail, n*

5/14

5/5

1/2

1/2

0/3

3/4

1/4

Mean size of cystic component (range), cm

1.3 (1.0–2.2)

1.1 (1.0–1.4)

2.3 (1.8–3.1)

6 and 11

1.4, 2.2, and 2.5

1.5 (1.0–2.5)

1.8 (1.0–3.4)

Pre-operative diagnosis of IPMN, n*,**

4/11

0/3

1/2

1/1

2/3

1/3

1/5

MRI findings

Unilocular and concentric at the distal side of the PDAC. High intensity on T2-WI.

Multiple cystic structures, some >1 cm within the PDAC. Relatively high intensity but less than that of cerebrospinal fluid on T2-WI.

Unilocular and round. High-intensity fluid on T2-WI.

N/A

Cysts in the groove area or duodenal wall.

Demarcated unilocular peripancreatic cysts with heterogeneous occasionally un-enhanced components.

Heterogeneous cystic lesions within the PDAC.

Pathologic findings

Round, unilocular, with smooth lining and open lumina. No contour irregularities. No papillary configuration. No classical cell types.

Irregularly distributed large ducts with jagged edges.

Lined by columnar mucinous cells often having deceptively bland cytological features. Variable degrees of papillomatosis.

A smooth internal lining composed of simple mucinous lining with occasional folding and atypia. No florid papilla formation.

A band of muscle coat and other epithelia (respiratory) and accessory mucous glands.

Cysts were lined partially by epithelium and hypercellular reactive tissue with stromal deposition of acinar secretions associated with inflammatory/fibroblastic reaction.

Partly hemorrhagic and necrotic.

Cyst wall composed of granulation tissue and fibro-inflammatory elements. Carcinoma cells were seen invading into and partially lining the inner layer of the fibro-inflammatory cyst wall.

In 3, the cystic component corresponded to acellular hyalinized material and the cyst wall also showed partially hyalinized and paucicellular stroma but also contained carcinoma cells. In 2 others, the cyst wall was composed of hypercellular inflammatory stroma.

Partial mucinous cyst lining, n**

15/15

6/6

4/4

2/2

2/3

4/5

3/5

Colonization by carcinoma, n

14/15

–

–

–

0/3

3/5

0/5

PanIN in the uninvolved pancreas, n**,***

6/6 (4 HG-PanIN, 2 LG-PanIN)

3/3 (2 HG-PanIN, 1 LG-PanIN)

2/2 (1 HG-PanIN, 1 LG-PanIN)

0/2

2/2 (HG-PanIN)

2/3 (HG-PanIN)

1/2 (HG-PanIN)

  1. PDAC pancreatic ductal adenocarcinoma, PDP paraduodenal pancreatitis, IPMN intraductal papillary mucinous neoplasm, MRI magnetic resonance imaging, T2-WI T2-weighted image, N/A no available data, LG-PanIN low-grade pancreatic intraepithelial neoplasia, HG-PanIN high-grade pancreatic intraepithelial neoplasia.
  2. *Results of pre-operative imaging studies were available to the authors in 27 of 40 patients with pseudo-IPMN.
  3. **One case had both paraduodenal wall cyst and cystically necrotic tumor.
  4. ***Adequate slides representing the uninvolved pancreas were available in 18 patients.
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