Plasmacytoma is a malignant lymphoproliferative disease that originates from clonal proliferation of malig- nant B-lymphoid cells. The disease is characterised by ostelolysis, monoclonal immunoglobulin in serum, or urine and monoclonal plasmacyte infiltration in bone marrow. Biclonal or triclonal paraproteins are not uncommon. Rarely non-secreting or non-exereting plasmacytomas can be seen. In 1–10 % of plasmacytoma cases; the disease is extramedullary. 12 % of these variants are localised in the gastrointestinal tract. The combination of biclonal plasmacytoma, non-excreting, plasmacytoma and gastrointestinal localisation is pro- bably rare. We did not find such a care in the literature. We are presenting the clinical and laboratory picture of a patient with a plasmacytoma and secondary involvement of the oesophagus, which has a different expres- sion of the immunoglobulin light chain. Monitoring of the clinical course is difficult in this type of diagnosis because results of classical tests can be misinterpreted as low activity of the disease.

        Key words: secondary extramedullary plasmacytoma – non-excreting clone – biclonal plasmacytoma – oesop-