Tuberculosis is a multisystem infectious disease that most commonly occurs in the lung. Abdominal tuberculosis is one of the most common types of extrapulmonary tuberculosis. However, abdominal tuberculosis involving the pancreas and peripancreatic lymph nodes is rare.
The clinical manifestations of pancreatic tuberculosis include a generally insidious onset with non-specific constitutional symptoms, while the most common symptoms include abdominal pain, anorexia, weakness, fever, weight loss and night sweats(1). Obstructive jaundice is a common clinical manifestation in pancreatic head carcinoma, but is uncommon in pancreatic tuberculosis (2–4). Laboratory examinations are often non-contributory, including abnormal liver function tests, anemia, leukocytosis or elevated erythrocyte sedimentation rate (5).
The diagnosis of pancreatic tuberculosis is difficult prior to laparotomy in the majority of reported cases (6). Since pancreatic tuberculosis may be cured with antituberculosis therapy, it is important to make a definitive diagnosis on imaging in order to avoid unnecessary surgical interventions. Abdominal tuberculosis involving the pancreas and peripancreatic lymph nodes may mimic pancreatic carcinoma solely based on radiological findings, as in the present case. CT scan is the standard diagnostic option and was applied in the majority of the reported studies. The CT scan characteristics of pancreatic tuberculosis are non-specific, including low density, heterogeneous enhancement, peripheral enhancement, areas of central enhancement and presence of calcifications (6). A low-density mass around the pancreatic head with peripheral rim enhancement on CT, as in the present case, appears to be characteristic of lymphadenitis (3). These findings may result from the central caseous necrosis with peripheral active inflammation of infected lymph nodes (7).
MRI may be assist in the diagnosis of pancreatic tuberculosis. On T1-weighted images, the lesions may exhibit low intensity, and on T2-weighted images they may exhibit high intensity (8, 9). Peripheral rim enhancement may also be observed on post-contrast T1-weighted images, similar to the findings on CT. In addition, dilatation of intrahepatic and extrahepatic bile ducts may occasionally be observed on MRCP (2, 3). Generally, dilatation of the common bile duct and pancreatic duct (double duct sign) on MRCP is highly suggestive of a pancreatic head malignancy. However, pancreatic duct dilatation rarely appears in pancreatic tuberculosis, even if the lesion is located centrally in the head of the pancreas.
Abdominal tuberculosis presenting as a pancreatic head mass may encase and compress the portal vein, thus causing portal hypertension and gastric varices (10). Vascular invasion of the abdominal vessels is often considered as a characteristic of a locally advanced pancreatic malignancy. However, vascular involvement cannot be used as a criterion for discriminating pancreatic tuberculosis from pancreatic malignancy, as there are several reports of vascular involvement in pancreatic tuberculosis (11, 12). Abdominal imaging of pancreatic tuberculosis may reveal solid or cystic lesions, typically in the pancreatic head. Therefore, the main differential diagnoses include mucinous/serous cystadenoma, cystic neuroendocrine tumor and pancreatic adenocarcinoma, whereas pancreatic tuberculosis mimicking pancreatic abscess has also been reported (13).
Since the diagnosis of pancreatic tuberculosis from radiological images is difficult, histological or bacteriological confirmation is recommended for establishing the diagnosis. Usual biopsy methods include percutaneous ultrasound-guided or CT-guided biopsy, endoscopic ultrasonography-guided fineneedle aspiration (EUS-FNA), and open surgical or laparoscopic biopsy. EUS-FNA has been increasingly used to confirm the diagnosis(4, 14), and was reported to be safe and effective for sampling(8, 15). However, EUS-FNA has the risk of complications or tumor dissemination in potentially resectable malignant tumors. Another drawback of EUS-FNA is the difficulty in obtaining a sufficient sample for definitive diagnosis. Last but not least, This is not a routine preoperative diagnosis method recommended by the mainstream of China. Therefore, an operation with an incisional biopsy may be a suitable alternative for diagnosing pancreatic tuberculosis, as in the present case. Cytological biopsy in pancreatic tuberculosis shows caseous necrosis, granulomatous inflammation, epitheloid histiocytes, multinucleated giant cells and lymphocytes, while acid-fast bacilli are rarely seen(10, 16). A positive culture for mycobacteria may confirm the diagnosis, but it is less sensitive and requires long incubation periods.