Adenosquamous carcinoma of the pancreas
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Adenosquamous carcinoma of the pancreas is a rare, highly aggressive malignancy, clinically indistinguishable from the more common pancreatic ductal adenocarcinoma. Their defining pathological and imaging characteristics are the frequent presence of central necrosis and vascular invasion.
These tumors have been variably referred to as adenoacanthomas, mixed squamous and adenocarcinomas and mucoepidermoid carcinomas 10.
Adenosquamous carcinoma makes up ~5% (range 1-10%) of all exocrine pancreatic malignancies 8,9.
These tumors occur in older adults (mean age of 68 years) 9, with a slight male predilection (M:F = 1.5:1) 7.
Adenosquamous carcinoma exhibits the same clinical characteristics as the more common pancreatic ductal adenocarcinoma and distinguishing between the two based on clinical findings alone is not possible 8.
The diagnosis of an adenosquamous carcinoma requires at least 30% squamous histology present in the tumor 10.
Tumors exhibiting a lower proportion of squamous cells are termed “pancreatic cancer with squamous differentiation” 7.
Adenosquamous carcinomas typically appear as ill-defined, lobulated lesions 4-6,9, hypoattenuating or isoattenuating on non-enhanced CT 4,6.
On contrast-enhanced CT the majority of these tumors exhibit a central hypodense, non-attenuating area of variable size corresponding to necrosis, a characteristic that differentiates them from pancreatic ductal adenocarcinomas 2,3,5,9.
A defining feature of adenosquamous carcinoma is progressive ring enhancement 6,9. Invasion of the adjacent vessels and tissues is frequent 2,4-6. Dilatation of the main pancreatic duct upstream to the lesion can be seen in about 50% of adenosquamous carcinomas 4-6. Calcification and hemorrhage are not typical features of these tumors 2-4,6.
The solid component of the tumor exhibits a decreased signal compared to normal parenchyma on T1WI and increased signal on T2WI 4-6. DWI shows a slight hyperintensity, with hypointensity on ADC images 6.
Ring enhancement can usually be better appreciated on MRI 6.
Treatment and prognosis
Due to the relative rarity of these tumors there are no established treatment protocols 8. The only available treatment is resection, with a median survival of 12 months 1.
History and etymology
The earliest description of this tumor was by the German pathologist, Gotthold Herxheimer (1872-1936), in 1907 who called it a "cancroide" 10.
necrosis less common (40% vs 100%)
tumor thrombi are rare (6% vs 37.5%) 5
adenosquamous carcinoma is more often located in the pancreatic tail 9
calcification present in 50%
may exhibit calcification
usually well encapsulated
may show calcification
typically in young women
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- 9. Schawkat K, Manning M, Glickman J, Mortele K. Pancreatic Ductal Adenocarcinoma and Its Variants: Pearls and Perils. Radiographics. 2020;40(5):1219-39. doi:10.1148/rg.2020190184 - Pubmed
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