A 65-Year-Old Man Comes to the Office Due to 4

A 65-year-old man comes to the office due to 4 months of worsening fatigue and constant, low back pain.  The patient feels tired with simple household chores.  He has a 15-pack-year smoking history and drinks 2 or 3 beers daily.  Temperature is 37 C (98.6 F) , blood pressure is 134/86 mm Hg, and pulse is 76/min.  Physical examination reveals a late systolic ejection murmur with a soft S2.  The lungs are clear to auscultation.  The abdomen is soft and nontender with no hepatosplenomegaly.  There are no focal neurological deficits.  Laboratory testing reveals hemoglobin is 9 g/dL and mean corpuscular volume is 93 µm³. 24-hour urinary protein excretion is elevated.  Imaging of the spine demonstrates diffuse osteopenia and multiple irregular, radiolucent lesions in the thoracic and lumbar vertebrae.  Which of the following histopathologic findings is most likely associated with the development of this patient's bone lesions?

A) Branching papillae lined by cuboidal cells with overlapping nuclei
B) Infiltrating glandular cells with substantial adjacent osteoblasts
C) Large, malignant cells containing keratin and intercellular bridges
D) Clusters of mature plasma cells and plasmablasts
E) Sheets of round or polygonal cells with abundant clear cytoplasm