Primary extraosseous plasmacytoma of the parotid gland: A case report and literature review

Extraosseous plasmacytoma (EOP) is an uncommon malignant tumour that is characterised by the monoclonal proliferation of abnormal plasma cells in soft tissue; however, EOP lacks the defining features of multiple myeloma or medullary plasmacytoma. Although the majority of EOP lesions occur in the head and neck, EOP of the parotid gland is extremely uncommon. The present study aimed to explore the clinical features of parotid plasmacytoma, in addition to the diagnostic and therapeutic options for its management. Using the Medline database, a search was conducted for articles published on the topic of 'parotid plasmacytoma' up until the year 2016. A total of 20 cases were evaluated, including 19 clinical cases from the literature and 1 new clinical case from our hospital. Among the 19 previously published cases, the mean age at the time of diagnosis of EOP was 65.1±10.9 years (range, 38-78 years). Plasmacytomas were located unilaterally in all cases: On the right side in 9 patients (47.4%), on the left side in 10 patients (52.6%). Treatment included chemotherapy in 3 cases, radiotherapy in 11 cases and surgical removal in 15 cases. The diagnosis of EOP is based on the presence of a localised tumour comprising monoclonal plasma cells, and EOP is identical to multiple myeloma in this regard; however, EOP, in contrast to multiple myeloma, does not exhibit the signs that are indicative of disseminated disease, such as additional lesions on skeletal radiological examination, plasmacytosis in the bone marrow, and hypercalcaemia, anaemia, or renal failure. Thus, EOP must be considered in the differential diagnosis of parotid gland lesions in order to avoid confusion with other tumoural diseases.