[PTHrP-producing diffuse large B-cell lymphoma presenting with hypercalcemia at diagnosis].

Area of Science:

• Oncology
• Hematology
• Endocrinology

Background:

• Diffuse large B-cell lymphoma (DLBCL) is an aggressive non-Hodgkin lymphoma.
• Parathyroid hormone-related protein (PTHrP) is typically associated with humoral hypercalcemia of malignancy.
• PTHrP-producing DLBCL is an extremely rare subtype with poorly understood characteristics.

Purpose of the Study:

• To report a rare case of PTHrP-producing DLBCL.
• To describe the clinical presentation, diagnostic workup, and treatment response.
• To highlight the potential for effective management of this rare lymphoma subtype.

Main Methods:

• Case report of a 55-year-old man presenting with symptoms suggestive of hypercalcemia and lymphoma.
• Laboratory investigations including serum creatinine, corrected calcium, and PTHrP levels.
• ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for staging and response assessment.
• Bone marrow biopsy with immunohistochemical staining (CD20, BCL-6, MUM1, PTHrP, PTH1 receptor).
• Treatment with R-CHOP chemotherapy followed by autologous peripheral blood stem cell transplantation.

Main Results:

• The patient presented with weight loss, somnolence, dysarthria, elevated creatinine, hypercalcemia, and elevated PTHrP.
• ¹⁸F-FDG PET/CT revealed splenomegaly and widespread bone marrow involvement.
• Bone marrow biopsy confirmed DLBCL with neoplastic cells positive for CD20, BCL-6, MUM1, PTHrP, and PTH1 receptor.
• Treatment led to undetectable PTHrP levels after one R-CHOP cycle and complete metabolic response on PET/CT after four cycles.
• The patient achieved long-term complete remission following stem cell transplantation.

Conclusions:

• PTHrP-producing DLBCL, though rare, can be effectively managed with standard lymphoma treatment protocols.
• Prompt diagnosis and multi-modality treatment, including chemotherapy and stem cell transplantation, are crucial for achieving remission.
• Further research is warranted to elucidate the pathophysiology and specific characteristics of PTHrP-producing DLBCL.