Tuberculosis presenting as a pancreatic cystic neoplasm

Abstract

A 33-year-old Thai born woman was referred to our tertiary referral hospital with back and epigastric pain. Investigations included abdominal ultrasound and CT scan of the abdomen which demonstrated a 3 cm cystic lesion in the head of the pancreas, most likely a mucinous cystadenoma. Because of its malignant potential resection was advised. During surgical exploration, the tumour appeared unresectable, due to involvement of the common hepatic artery. PCR on biopsy revealed Mycobacterium tuberculosis. The patient was referred to an infectious disease specialist, and a full recovery was achieved after 6 months of antimicrobials.

Background

With the increasing numbers of diagnostic abdominal CT and MRI scans performed, more incidental (cystic) pancreatic neoplasms are identified.¹ Main duct intraductal papillary mucinous neoplasm (IPMN) and large mucinous cystic neoplasm have a malignant potential, and therefore, timely resection is advised.² Characterising these lesions however, based only on cross-sectional morphology has proven to be difficult. One retrospective review of 330 patients with incidental cystic neoplasms of the pancreas reported a match between preoperative cytology and postoperative histological diagnosis as low as 68%.³ Endoscopic ultrasound (EUS) is added to evaluate worrisome features. If worrisome features are present, surgical resection to prevent possible malignant transformation is advised. This case illustrates misdiagnosis of pancreatic tuberculosis (TB) presenting as a pancreatic cystic neoplasm.

Case presentation

A 33-year-old woman presented with a 6-month history of intermittent back pain radiating via the left flank to her left leg. There were no neurological deficits, but the symptoms were sometimes accompanied with epigastric pain. She had fatigue and shortness of breath but no weight loss, jaundice, diarrhoea or steatorrhoea. She was born in Thailand and migrated to the Netherlands 12 years ago. She drank 45 units of alcohol weekly and was a previous smoker. She had no family history of gastrointestinal or pancreatic cancer. Shortly after arriving, she was diagnosed with sensitive pulmonary TB and completed the standard 6-month therapy consisting of isoniazid, rifampicin, ethambutol and pyrazinamide for 2 months and isoniazid, rifampicin for another 4 months. In 2012, she was discharged from further follow-up by her infectious disease specialist.

Investigations

Examination revealed an obese woman with mild epigastric tenderness but without jaundice or other remarkable findings. Preoperative laboratory tests including haemoglobin, white blood cell, C-reactive protein, electrolytes, CA19.9, Carcinoembryonic antigen (CEA) were all unremarkable. Ultrasound of the abdomen was performed, revealing a 3.4×3.0 cm cystic lesion in the pancreatic head with no duct dilatation or increased vascularity. A chest X-ray was unchanged compared with previous post-TB X-rays.

A contrast enhanced CT scan of the abdomen showed a 4.4×3.3 cm irregular cystic mass in the head of the pancreas (figures 1 and 2), without connection to the pancreatic duct. The pancreatic duct was not dilated. The mass showed <90° involvement of the common hepatic artery without signs of enlarged lymph nodes or distant metastases. The mass was assessed with EUS, which confirmed a cystic lesion in head of the pancreas (figure 3). Fine needle aspiration (FNA) showed purulent material with a low cell count, on which a definite diagnosis could not be confirmed by cytology.

Figure 1.

Axial CT image showing the cystic mass (*) in the pancreatic head. Arrow points to the nodular lesion.

Figure 2.

Axial CT image with the cystic lesion in the pancreatic head (*). Arrow pointing to tumour involvement of the celiac axis and common hepatic artery.

Figure 3.

Endoscopic ultrasound, showing hypoechoic lesion (*) in head of the pancreas. Arrow points towards solid component.

Differential diagnosis

Based on imaging, the primary differential was a mucinous cystic adenoma with worrisome nodular degeneration. Vascular involvement suggested borderline resectability and an exploratory laparotomy was undertaken through a subcostal incision with the aim to perform a resection of pancreatic head and body.

Treatment

Operative findings

During surgical exploration, a solid lesion arising from the pancreatic head was identified. Assessment of the vascular involvement showed that the common hepatic artery, gastroduodenal artery and the base of the coeliac trunk were involved >90°. Based on these findings it was concluded that the lesion was not resectable, however frozen section at that time could not confirm malignancy nor an alternative diagnosis. A biopsy was performed and the content of the cyst was aspirated and sent for microbiological and histopathological assessment.

Microbiological findings and additional examinations

Histopathology showed non-specific inflammation without granulomas and no signs of malignancy. Cytology was non-diagnostic. Because of the patient’s background and lack of alternative diagnosis a PCR for Mycobacterium tuberculosis was performed, which was positive. Postoperative work-up for TB included sputum PCR for M. tuberculosis, Ziehl–Neelsen staining, and HIV serology, all of which came back negative. On revisiting the history the patient admitted to a chronic cough with occasional haemoptysis. A CT scan of the chest showed a cavitating lesion in the left upper lobe which had not been seen on previous scans during her first treatment course for TB (figure 4). Based on these findings, the diagnosis of pulmonary and pancreatic TB in an immunocompetent patient was made.

Figure 4.

Coronal CT image showing the caveating lesion (*) of the left superior lobe.

Outcome and follow-up

The patient was referred to an infectious disease specialist. Multiple sputum samples came back negative for TB, but the combination of positive PCR on biopsy material and cavitating lesion on the chest CT scan was considered enough evidence to start medical treatment with isoniazid, rifampicin, ethambutol and pyrazinamide. After 6 months of therapy, the patient was clinically fully recovered. A follow-up CT scan showed regression of the pancreatic cystic mass and no progression of her pulmonary lesion.

Discussion

We present an unusual case of a cystic lesion in the pancreas which was found to be TB. Our patient had a history of TB for which she had already completed a full treatment course without signs of recurrence during a 5-year follow-up. At presentation, she had no signs of infection and was immunocompetent.

TB has been dubbed the great mimicker of diseases. However, a pancreatic presentation of TB is rarely reported.⁴ Diagnosing isolated pancreatic TB with abdominal ultrasound or CT has proven to be difficult.⁵ According to one retrospective series, the use of EUS with FNA correctly diagnosing pancreatic TB in only 16 out of 21 cases (76%).⁶

Literature on pancreatic TB consists mostly of case reports or case series. We have found no epidemiological reports on incidence of pancreatic TB. The largest case series was published by Nagar and colleagues in 2009.⁷ Out of 384 patients with abdominal TB 32 patients (8.3%) had pancreatic involvement. These patients averaged 42.5 years and typically presented with abdominal pain, nausea, vomiting and weight loss. Only 14 out of 32 patients had previously diagnosed TB, of which 11 reported to have completed prior treatment. Jaundice was a rare presenting symptom in only 3/32 patients. CT scan most commonly showed a bulky heterogeneous pancreas or a solitary parenchymal lesion. Pancreatic head and body are the most commonly affected locations. Peripancreatic lymph nodes were pathologically enlarged in most cases (24/32).

Pancreatic cysts are found more often due to the increasing use of diagnostic imaging techniques such as ultrasound and CT scans.¹ With the malignant potential of cystic neoplasms a final diagnosis must be made, sometimes requiring surgical resection. Pancreatic cystic lesions can be classified into three main groups: pseudocysts, common cystic neoplasms and uncommon cystic neoplasms. Without a history of pancreatitis, cholelithiasis or trauma a pseudocyst is considered very unlikely. Common cystic neoplasms are IPMN, which arises from pancreatic duct cells. Mucinous cystic neoplasm are unilocular cysts mainly seen in women and with peak incidence at the age of 40–50 years. Serous cystic neoplasms often present with a central scar and calcifications and are found more often in women aged 60–70 years. Uncommon cystic neoplasms include the solid pseudopapillary neoplasms found mainly in young women (15–25 years) and neuroendocrine tumours with cystic degeneration.

Conclusion

This case illustrates the need for increased awareness in low endemic TB countries regarding extrapulmonary TB. In cases where TB is suspected, TB PCR should be considered alongside routine work-up to exclude pancreatic malignancy. The importance of a multidisciplinary team for assessment of pancreatic pathology and the reminder that even with our current armada of imaging tools the great mimicker of diseases, TB, still holds true to its name.

Learning points.

• The differentiation of cystic lesions in the pancreas is complex. Intraductal papillary mucinous neoplasm and mucinous neoplasm require excision because of malignant potential.

• Although rare, tuberculosis (TB) may be an origin of a pancreatic cyst, especially in patients coming from endemic TB countries or with prior history of TB.

• Pancreatic TB usually arises as a solid mass, however may also present as a cystic lesion.

• If pancreatic TB is suspected, an endoscopic ultrasound guided fine needle aspiration for both histopathology and microbiology including PCR should be performed.

• Knowledge of different presentations of TB, including visceral and even isolated pancreatic presentation will help clinicians recognise this disease in low endemic areas.