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A 79-year-old man presented with signs of biliary obstruction (bilirubin 82 μmol/L, alanine aminotransferase 358 IU/L and alkaline phosphatase 250 IU/L) and normocytic anaemia (haemoglobin 120 g/L). He had a 4-month history of relapsed multiple myeloma and had been treated with five cycles of bortezomib (a proteasome inhibitor). Transabdominal ultrasound demonstrated an ill-defined mass in the pancreatic head associated with upstream biliary dilatation. CT demonstrated multiple uniformly enhancing soft tissue masses throughout the pancreas with enlargement of the pancreatic head, in particular, and associated biliary obstruction. There was a direct invasion into the main portal vein, suggesting a solid malignancy. There was no evidence of distal metastases, ascites or peritoneal carcinomatosis (figure 1). Immunoglobulin (Ig) G4 levels were normal but IgG2 levels were elevated (23.4 g/L). Cancer antigen 19-9 was mildly elevated (32 kU/L). Endoscopic retrograde cholangiopancreatography and biliary stent placement were performed (figure 2), with a fall in bilirubin to 39 μmol/L. Biliary brush cytology was non-diagnostic.
Endoscopic ultrasound demonstrated a globally abnormal and expanded gland, which was predominately hypoechoic but with several foci of mixed echogenicity and evidence of ascites (figure 3). A 22 g fine needle biopsy (Acquire; Boston Scientific, Nantucket, Massachusetts, USA) was performed with three passes into the body of pancreas.
What is the most likely diagnosis and what differentials should be considered?
What supplementary investigations should be considered on the tissue sample?
Histopathology of biopsy cores demonstrated diffuse infiltration by atypical plasma cells (figure 4). Immunohistochemistry showed an abnormal plasma cell phenotype consistent with infiltration of the pancreas by extramedullary myeloma. Without clinical context, a differential is an extraosseous plasmacytoma.
Multiple myeloma, a neoplastic plasma cell disorder, accounts for 13% of haematological malignancies.1 The median age of diagnosis is 69 years and two-thirds of patients are male.2 Positron emission tomography (not performed in our patient) is sensitive to extramedullary myeloma, a systematic review of nine studies found rates of ranging from 2%–27%.3 Prevalence increases with duration of disease, age and number of previous therapies. The skin and subcutaneous soft tissue are the most common extramedullary foci, accounting for 69%,4 followed by liver, kidneys and central nervous system.5 Extramedullary disease is associated with multiple poor prognostic factors, and overall survival for an extramedullary relapse is <6 months.6
Extramedullary involvement of the pancreas is a rare entity, seen almost exclusively in the context of established multiple myeloma.7 This case is unique in demonstrating macroscopic venous invasion and this feature should not exclude haematological malignancy from the diagnosis.
Contributors MJK and JB were involved in the literature review and drafted the manuscript layout, text content and sourcing images. MJK, JB, RA and MTH were involved in revisions of the manuscript layout and content. AW and AC advised on histopathology input and provided the demonstrative histopathology image.
Funding This research has received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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