Pancreatic Squamous Cell Carcinoma: A Rare Histologic Subtype

Abstract

Pancreatic squamous cell carcinoma is an extremely rare histological variant of pancreatic cancer as pancreas does not have squamous cells. Etiology is not well understood and only few cases have been reported in the literature so far. Here, we present a case of a patient with this diagnosis. 83-year-old male was referred for endoscopic ultrasound (EUS) evaluation and management of recurrent pancreatitis of unknown etiology. MRI done at outside facility showed a 1.5x1.5 cm cystic mass in the tail of the pancreas. He had undergone Endoscopic retrograde cholangiopancreatography (ERCP) and biliary stenting at the outside hospital and been asymptomatic since. Laboratory workup showed normal Liver enzymes and CA 19-9 of 122. EUS showed normal pancreatic parenchyma and duct with a solid cystic mass 2x2 cm at body/tail junction, which was biopsied using fine needle core biopsy technique. Cytology and immunostaining showed the tumor to be strongly diffusely p63 positive and CK7 negative, which is consistent with squamous cell carcinoma. Staging CT scans were performed showing no metastatic disease or other primary origin of this squamous cell carcinoma. He was managed with distal pancreatectomy and splenectomy following neo-adjuvant chemotherapy. Pure pancreatic squamous cell carcinoma is very rare with a reported incidence of 0.005% of all exocrine pancreatic tumors. It usually occurs in elderly. Exact pathogenesis is still controversial but different theories have been suggested regarding its origin including squamous metaplasia during episodes of acute pancreatitis and subsequent malignant transformation, and presence of primitive cells in the pancreas with ability to differentiate into squamous cells undergoing malignant transformation. Considering the rarity of this histologic subtype, physicians should be cautious in evaluating these patients and need to rule out metastatic squamous cell carcinoma from another primary before presuming it as a pancreatic primary. Our patient was asymptomatic and CT scans showed no metastatic disease or other primary source for his malignancy. Surgical resection is curative only in a minority of patients as the disease is usually widely metastatic at the time of diagnosis, with a poor prognosis. In conclusion, pancreatic squamous cell carcinoma is a rare tumor with a controversial etiology. Ruling out another primary origin before making such diagnosis is very important.Figure: CT scan images show 2.4 x 1.9 cm sized well-circumscribed rim enhancing hypodense lesion in the tail of the pancreas.Figure: EUS (upper left) shows a solid cystic mass 2x2 cm at body/tail junction. EUS-guided fine needle core biopsy shows a pancreatic lesion nested in appearance (upper right) which shows on a closer view (bottom left) whorls or keratin pearls which is very characteristic of squamous cell carcinoma. Immunostaining (bottom right) shows strong p63 positivity and CK7 negativity which is consistent with squamous cell carcinoma.