Pancreatic Pathology Online
Reporting of Pancreatic Biopsies for diagnosis of Neoplastic Lesions
These are almost always taken for lesions of the exocrine pancreas.
Chronic pancreatitis can mimic neoplasia clinically and radiologically as it may form a mass in the head of the gland.
On biopsy similar confusion can arise : Pancreatic adenocarcinoma is often desmoplastic and can closely resemble chronic pancreatitis in which there is distortion of acni and ducts by dense fibrosis.
Microscopical report :
If a neoplasm is present, the report should comment on the:
- Cystadenoma : Microcystic ; Serous ; Mucinous ;
- Adenocarcinoma and subtypes : Adenosquamous ; Mucinous ; Papillary cystic ;
- Anaplastic carcinoma ;
- Acinar cell carcinoma ;
- Squamous cell carcinoma (probably metastatic) ;
- Giant cell tumour ;
- Pancreatoblastoma ;
- Lymphoma (NHL or Hodgkin's).
Spread: Perineural ; Intravascular ; Extrapancreatic;
Associated inflammatory changes.
When no-neoplastic tissue is present in the biopsy, the report should commont on the appearances of the:
Acini: Dilatation, atrophy, necrosis ;
Ducts: Dilatation, hyaline casts, periductal fibrosis, inflammation, squamous metaplasia ;
Vessels: Vasculitis , necrosis, thrombosis ;
Inflammation: Acute, active, chronic, granulomatous ;
Hemorrhage: Diffuse or focal ;
Fibrosis: Site and extent ;
Calcification: Site, including peripancreatic tissues ;
Iron deposition: As seen in haemochromatosis and haemosiderosis.
Several prognostically important histopathological features have been determined for pancreatic exocrine carcinoma and these should be assessed and recorded.
The tumour type and grade should be determined.
The tumour size and distance from the anterior peritoneal surface and both the retroperitoneal and pancreatic (if applicable) surgical margin should be confirmed microscopically since macroscopic assessment alone may lead to inaccuracy due to co-existent chronic pancreatitis.
The presence of lymphovascular and/or perineural tumour invasion should be noted.
The common bile duct surgical margin should be examined for evidence of dysplasia or invasive tumour.
Lymph node status is a powerful predictor of survival and the presence, number and position of any tumour-involved nodes should be clearly noted.
The individual components of the TNM staging system are independent prognostic factors and therefore the TNM stage of the tumour should be recorded.
A brief description of the background gastric and duodenal mucosa is also recommended.
Additional prognostic factors:
Several individual studies have suggested that the MIB-1 labelling index, p53 and Bcl-2 labelling and DNA ploidy are independent prognostic factors in pancreatic adenocarcinoma. However, these additional techniques have yet to be adopted into routine clinical practice.
Frozen section and needle biopsy assessment:
Confident distinction of well differentiated adenocarcinoma from chronic pancreatitis may be very difficult in these small specimens and the two conditions frequently co-exist.
A firm diagnosis may not always be possible.
Features favouring malignancy include marked nuclear size variation between ductal epithelial cells, incomplete ductal lumens, disorganized ductal distribution, large irregular nucleoli, necrotic glandular debris, glandular mitotic figures and perineural invasion.
Rarer forms of pancreatic exocrine carcinoma include adenosquamous carcinoma, pleomorphic giant cell carcinoma (an anaplastic tumour in which there are malignant giant cells) and osteoclast-like giant cell tumour (a malignant anaplastic epithelial tumour admixed with osteoclast-like giant cells).
Analysis of such tumours for mutations of the Ki -ras oncogene suggests that they are variants of pancreatic adeno-carcinoma with a similar prognosis.
Acinar cell carcinomas are very rare.
Macroscopically there are lobules of tumour cells separated by fibrous bands.
Acinar areas, trabecular and solid areas are all found histologically and the relatively uniform tumour cell morphology can lead to confusion, particularly with endocrine tumours.
Acinar tumors are cytokeratin positive as well as staining for pancreatic enzymes such as trypsin and lipase.
Endocrine tumours will stain for synaptophysin and chromogranin but focal staining for these endocrine markers can be seen in acinar tumours.
Study of Ki-ras mutations suggests that these tumors have a different histogenesis from pancreatic ductal carcinomas although the prognosis is not dissimilar.
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