A Rare Case of Pancreatic Ductal Adenocarcinoma with Ossification Mimicking a Pancreatic Stone Impaction

A 39-year-old man presented with epigastralgia. The patient drank socially. The initial blood tests showed no abnormalities. Computed tomography revealed a calcified lesion (6 mm × 5 mm) in the pancreatic body with a distal dilated main pancreatic duct [Figure 1a]. A tumorous lesion was not identified. The patient was diagnosed with pancreatic stone impaction, and we attempted to remove the pancreatic stone. However, the pancreatography showed that the lesion was not a pancreatic stone but a stricture in the pancreatic body [Figure 1b]. Brush cytology from the stricture revealed Class IIIb. EUS showed a low echoic and circular lesion around the calcified lesion [Figure 1c], although the low-echoic lesion could not be distinguished from the low-echoic distal pancreatic parenchyma. EUS-guided fine-needle biopsies of the low-echoic lesion around the calcification revealed suspicious adenocarcinoma. Therefore, a middle pancreatectomy was performed. Macroscopically, a white nodule with a 16-mm diameter was found on the cut surface of the pancreatic body [Figure 2a]. Microscopically, mature and immature osseous tissue was observed in the center of the lesion [Figure 2b]. Atypical columnar epithelial cells with irregularly shaped nuclei surrounded the osseous region. The epithelial cells contained rough chromatin, and the proliferating cells formed distorted tubules or small nests of moderately to poorly differentiated adenocarcinoma. Joining of the tumor cells with the osseous tissue was also observed [Figure 2c]. The tumor cells were immunohistochemically negative for p40, indicating no metaplastic change for squamous cell carcinoma. The final pathological diagnosis was a pancreatic ductal adenocarcinoma (PDAC) with ossification at stage T1N0M0.Figure 1: (a) Contrast-enhanced computed tomography showing a calcified lesion (6 mm × 5 mm) (allow) in the pancreatic body with a distal dilated main pancreatic duct. (b) Endoscopic retrograde pancreatography showing a stricture in the pancreatic body with a distal dilated main pancreatic duct instead of a pancreatic stone. (c) EUS showing a low echoic and circular lesion around the calcified lesion in the pancreatic bodyFigure 2: (a) Macroscopically, the nodule on the cut surface in the pancreatic body appeared as a 16-mm white nodular lesion. (b) An irregularly shaped ossified lesion was observed in the center of the tumor on the loupe image. (c) Distorted neoplastic tubules of the adenocarcinoma intermingled with ossified tissue. (H and E, ×100)PDAC with ossification is extremely rare, and only one autopsy case with multiple metastases has been reported in English-language literature.[1] To the best of our knowledge, this is the first reported patient with PDAC who underwent radical surgery at an early stage. Pancreatic stones frequently occur in patients with chronic pancreatitis. Although chronic pancreatitis may contribute to the development of PDAC, the pancreatic stones alone do not contribute to the malignancy.[2] This case was initially misdiagnosed as impaction of a pancreatic stone because the ossification mimicked a pancreatic stone. A quick diagnosis of pancreatic stones could hinder a correct diagnosis of PDACs with ossification. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.