Another important form of neoplastic plasma cells are plasmacytomas, which arise from soft tissue, where they are known as extramedullary plasmacytomas, or from bone, where they are known as solitary osseous plasmacytomas.

Plasma cell neoplasms originate from terminally differentiated B lymphocytes that have undergone malignant transformation.

Mammary tumors are the third most common feline cancer, 1-3 accounting for 10.3% to 12% of all diagnosed tumors.

Metastatic, disseminated, and locally infiltrative cancers, including metastatic carcinoma, melanoma, lymphoma, hemangiosarcoma, and histiocytic sarcoma, can often affect the hepatic parenchyma.