Incidental diagnosis of a rare pancreatic plasmacytoma with plasmablastic features

Abstract

Multiple myeloma is a plasma cell neoplasm that accounts for 10% of all hematologic malignancies, characterized by malignant proliferation of monoclonal plasma cells in the bone marrow. It predominantly affects men 60 to 70 years of age. Plasmacytoma is a discrete mass of neoplastic monoclonal plasma cells that may be osseous or extramedullary. Though extramedullary plasmacytomas are uncommon, they can involve any tissue or organ. Only a few cases of pancreatic involvement have been reported. We report a case of a 78-year-old woman with a long-standing history of multiple myeloma noted to have pancreatic tail involvement with plasmacytoma with plasmablastic features. Multiple myeloma with plasmablastic transformation has a poor prognosis; hence, a multidisciplinary team approach is crucial to identify and initiate appropriate management in these cases.

Most patients with multiple myeloma (MM) present with generalized disease at diagnosis; a minority of patients present with discrete masses of neoplastic plasma cells (plasmacytoma) either in bone or soft tissues, which may present as solitary lesions or as a relapse of MM.¹ We describe a case of pancreatic plasma cell myeloma with plasmablastic features found incidentally during routine surveillance and confirmed with a biopsy.

Case Presentation

A 78-year-old black woman was diagnosed with MM when she presented with weight loss, deranged renal function, and lytic lesions. At the time, bone marrow revealed 12% plasma cells, renal biopsy showed myelomatous deposition and elevated kappa light chain, and cytogenetics showed a 13q deletion, indicating a poor prognosis. Her first-line regimen was dexamethasone, with bortezomib for approximately 1 year, after which, due to suboptimal response, cyclophosphamide was added. During the extensive course of management, there were multiple complications in the form of a pathological left femur fracture, port infection in the second and third year of her disease course, bacteremia, and dementia. She required multiple blood transfusions intermittently.

Five years into her diagnosis, she developed iron overload in the liver, which improved over time spontaneously. A year after that, she had plasmacytomas in the jaw, neck, calvarium, and lung and therefore was started on lenalidomide and dexamethasone. This regime was eventually changed to pomalidomide with dexamethasone due to progressive disease. For increasing and bothersome plasmacytoma of the right lower extremity and right supraclavicular fossa, palliative radiotherapy was given. While on pomalidomide and dexamethasone, she developed an episode of severe sepsis and therefore had to be intubated. With the antibiotic coverage and supportive therapy, she improved and was discharged successfully.

A follow-up positron emission tomography–computed tomography scan showed further progression in the form of a lesion in the pancreatic tail mass to 7.3 × 5.3 cm with a maximum standardized uptake value of 15.3. A laparoscopic biopsy was done, and histopathological examination was positive for plasma cell myeloma with plasmablastic features. The patient presently has an Eastern Cooperative Oncology Group performance status of 3, and she is currently being treated with supportive therapy alone. However, the option of further treatment with chemotherapy plus palliative radiation therapy has been discussed with her.

Discussion

Extramedullary involvement as plasmacytomas represents 3% to 4% of all plasma cell neoplasms, of which the head and neck area accounts for 80% to 90% of tumors; gastrointestinal involvement has been reported in 10% of extramedullary plasmacytomas, with liver, spleen, or stomach being the more common sites.^2–4 Pancreatic involvement of myeloma is relatively rare, with an incidence rate of 2.3% based on autopsy studies.⁵ Masses located in the pancreatic body or tail are more likely to be detected incidentally, and masses in the head of the pancreas^3,6 usually compress the biliary tree, leading to obstructive signs and symptoms.

Based on the analysis of Bartl et al, MM has been classified into six subtypes: Marschalko, cleaved, polymorphous, asynchronous, small cell, and blastic type.⁷ Plasmablastic myeloma is a blastic subtype and represents MM’s terminal evolution, accounting for 5% to 15% of cases, associated with worse outcomes due to rapid progression and multiorgan involvement.^8,9 It is characterized by the presence of ≥2% plasmablasts in the bone marrow aspirate. Cytologically, plasmablastic myeloma is distinguished by the presence of large-sized plasma cells containing large hyperchromatic nuclei, large nucleolus, cytoplasm with no or very little hof region, a high nuclear to cytoplasmic ratio, and an increased number of mitoses.¹⁰ Diagnosis is by imaging modalities such as ultrasonography, positron emission tomography, computed tomography and magnetic resonance imaging, endoscopic ultrasonography, and endoscopic ultrasonography–guided fine-needle aspiration. Confirmation is by the demonstration of monoclonal plasma cells and plasma cell markers, such as CD38 on immunohistology. Management involves a combination of local radiation, surgery, and combination chemotherapy. For tumors involving the pancreas head and neck, the treatment of choice is local radiation since they are highly radiosensitive. For tumors involving the pancreas tail, distal pancreatectomy can be considered in good surgical candidates.^11,12 Combination chemotherapy with bortezomib, thalidomide, lenalidomide, doxorubicin, or cyclophosphamide along with dexamethasone may be used in varying combinations in patients with primary progression or response followed by a progression of MM.

In conclusion, pancreatic plasmacytoma with plasmablastic features is a rare form of MM with very few reported cases. Although advances in the management of MM have increased life expectancy, it is crucial for clinicians to closely monitor patients with MM for plasmablastic transformation, given its aggressive nature with poor survival rates.