Short cases – Pancreas case 1 (FS) – NUS Pathweb

Pancreas case 1 (FS)

Case writer: A/Prof Nga Min En

Clinical history:

71M, history of pancreatic ductal carcinoma. Underwent neoadjuvant chemotherapy. Now undergoing Whipple resection.
Frozen section performed, specimen labelled as “retroperitoneal tissue”.
What are the histologic findings?
What are your differential diagnoses?
What clinical information would be helpful in your diagnostic workup?
What ancillary tests would you do?

Click picture to enlarge

Invasive malignant glands on the left appear morphologically similar to the glands invading the smaller nerve on the right.

In the context of known malignancy, in this case pancreatic ductal adenocarcinoma, the main concern is involvement by adenocarcinoma.

Hence the main differential diagnosis to consider is perineural invasion by adenocarcinoma.
Very rare instances of benign perineural “pseudoinvasion” have been documented, usually in chronic pancreatitis. This would be a very unlikely differential in the context of known malignancy.
At the time of the frozen section, it would be useful to know:
The histologic features of the pancreatic ductal adenocarcinoma e.g. the histologic type and grade. If well differentiated, this supports the histologic findings in the current sample as representing malignant glands.
The imaging findings e.g. is there gross residual tumour present after chemotherapy; are there any retroperitoneal masses?

Diagnosis

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Learning Points

When handling frozen sections of cases of known malignancy or tumours, it is useful to have an idea of the original tumour histology e.g. histologic type and grade.
It would also be useful to know the stage of any known primary cancer, and margin status, as and when relevant to the current frozen section.
Extremely rare instances of perineural “pseudoinvasion” have been described, sometimes by islet or benign ductal cells, often in the context of chronic pancreatitis. However, in a patient with known pancreatic malignancy, the presence of perineural glands is far more likely to represent true perineural invasion. The perineural glands must be carefully compared with the malignant glands.

References:

Goldman RL. Benign neural invasion in chronic pancreatitis.J Clin Gastroenterol. 1984;6:41–44
Costa J. Benign epithelial inclusions in pancreatic nerves. Am J Clin Pathol. 1977;67:306–307
Hauptmann K, Hauptmann S. Perineural pseudoinvasion in chronic pancreatitis. Pathologe. 2000;21:388–390