oral extramedullary plasmacytoma in a dog with a brief literature review

Plasma cell tumors are proliferation of differentiated b lymphocytes. this tumor is characterized by a mass of neoplastic plasma cells in either bone or soft tissue. multiple myeloma is malignant form of plasma cell tumors involving the bone marrow and it is the most common type of plasma cell tumors. plasmacytomas are localized plasma cell tumors which can be further classified as either osseous (involving bone) or extramedullary (involving soft tissue). extramedullary plasmacytomas are less common than osseous plasmacytomas and can develop in various locations such as skin, oral cavity and gastrointestinal tract. plasmacytoma are often treated with local therapies, like surgery or radiation and generally have a better prognosis than multiple myeloma. the aim of this report is histopathological description of oral extramedullary plasmacytoma in a dog. a 14-year-old female mixed-breed dog was referred to dental pet center for routine dental examination. a 10 mm to 8 mm oral mass was seen in buccal side of caudal oral cavity raised from gingival tissue of left maxillary forth premolar. the mass was soft, red with smooth surface. no bone invasion observed in intra-oral x ray. debulking of the mass was performed by surgical excision and submitted for histopathological examination. histopathological study revealed dense infiltration of neoplastic plasma cells. they arranged in sheets and nests beneath the gingival epidermis. the neoplastic cells were round to oval with eccentric nuclei, clumped chromatin, abundant cytoplasm. some of them showed perinuclear clearing. also, deposition of amyloid was seen around vessels and in the extracellular space which was confirmed by congo red. according to microscopic results oral extramedullary plasmacytoma was diagnosed. despite this tumor is relatively benign and patients display long survival time, there are some reports of progression or recurrence at the previous site of surgery. so proper surgical removal of oral extramedullary plasmacytoma is crucial for preventing recurrence. this report also highlights the utility of histopathology in the diagnosis of neoplasms.