Microscopic description and IHC:
The pap stain shows scattered atypical cells with dense and orange cytoplasm. Large cells with increased N/C ratio and small prominent nucleoli are present. There are extensive inflammatory cells in the background.
The resection specimen shows biphasic malignant growth with poorly differentiated adenocarcinoma and well to poorly differentiated squamous cell carcinoma.
Discussion:
Adenosquamous carcinoma is one of two common variants of ductal adenocarcinoma. The other variant is undifferentiated (anaplastic) carcinoma. The proportion of glandular vs squamous components can vary from tumor to tumor. Metastatic squamous cell carcinoma and squamous metaplasia should be considered in the differential.
In the original paper by Kardon et al, the author hypothesized the squamous carcinoma component may have originated from squamous metaplasia in the setting of chronic pancreatitis.
The prognosis for adenosquamous carcinoma of pancreas is worse than the usual ductal adenocarcinoma.