Periarticular plasma cell tumors in cats

Abstract

This report describes periarticular plasma cell tumors with abundant amyloid in 11 cats. The tarsus was the most commonly affected joint (10/11), and the masses were often circumferential around the tarsal joint, involving the dermis and subcutis. The 2 cases in which synovium was examined had neoplastic cells expanding the synovium. Three of the 5 cases staged radiographically had bony lysis of the affected joint. Cutaneous biopsy specimens often consisted of more amyloid than plasma cells, making the diagnosis difficult on small samples. Follow-up information was available in 7 cases; in those cases, the median survival was 194 days (range 53–671 days). Four cases had confirmed metastases, most often to regional lymph nodes, liver, and spleen. Although canine cutaneous plasma cell tumors are typically benign, those with abundant amyloid surrounding the joints of cats may involve deeper tissues and have a more aggressive behavior. These tumors can be difficult to diagnose due to low cellularity and abundant amyloid.

A series of heterogeneous lymphoproliferative diseases with CD3 and MUM1 co-expressed in cats and dogs

“…A 2022 report investigating feline periarticular tumors, primarily in the tarsus, found all cases labeled with MUM1, but CD3 and PAX5 was not investigated; these cases also often had abundant amyloid production. 7 Published data on B-cell antigen expression by plasma cells and our data on CD3 expression in plasma cells in this location call for further evaluation of feline tarsal lymphoproliferative disease to determine what fraction of these cases is a myeloma-related disorder with aberrant expression of CD3.…”

Cutaneous Plasmacytoma with Systemic Metastases in a Cape Serotine Bat (Laephotis capensis)

“…A case report of a primary duodenal plasmacytoma with associated amyloidosis in a cat found that the cause of death, 96 days after initial diagnosis and despite surgical removal of the mass and post-operative chemotherapy, was a result of a complication of the tumour itself and associated amyloidosis [ 9 ]. However, in general, the prognostic significance of amyloids currently remains unclear, with some studies finding an association with a more aggressive behaviour and others not finding any clinical correlation [ 4 , 14 , 38 ].…”

“…MUM1, encoded by the IRF4 gene, is a regulatory protein involved in the differentiation of B-lymphocytes to plasma cells and is required for immunoglobulin light-chain rearrangement. It is useful to identify plasmacytomas, MMs, and B-cell lymphomas in both canines and felines [ 6 , 14 , 19 ]. Indeed, of the B-cell markers commonly used in veterinary species, MUM1 is the preferred plasma cell marker for normal and neoplastic plasma cells, with one study reporting 84% of plasma cell tumours showing positive labelling, compared to 59/105 (56%) for CD79a and 21/108 (19%) for CD20 [ 39 ].…”

“…One study found the most frequent site of origin to be the skin [ 5 ], whilst other reports suggested oral plasmacytomas are the most common [ 1 , 2 , 3 ]. The incidence of plasmacytomas in cats is much lower, and the literature mostly consists of case reports of a single animal [ 7 , 8 , 9 , 10 , 11 ], although there are some studies with larger sample numbers ( n = 7–11) [ 12 , 13 , 14 , 15 ].…”

“…Indeed, although there have been reports of metastasis in a few cases of canine EMPs, these were located in the gastrointestinal tract and oral cavity, thus not of cutaneous origin [ 16 , 17 , 18 , 19 ]. By contrast, one study of cutaneous EMPs in felines found 4/11 (36%) cases developed metastasis [ 14 ], and metastasis has also been reported in EMPs from other sites [ 8 ].…”