SEER is an authoritative source of information on cancer incidence and survival in the United States. SEER currently collects and publishes cancer incidence and survival data from population-based cancer registries covering approximately 28 percent of the U.S. population.
Plasmacytoma refers to a malignant monoclonal plasma cell tumor growing within soft tissue.
Clonal proliferation of plasma cells cytologically and immunophenotypically identical to those of plasma cell myeloma but forming tumors at extraosseous and extramedullary sites. 80% occur in upper respiratory tract, including oropharynx, nasopharynx, sinuses, larynx.
Do not code primary site to C40._ or C41._. These category codes should only be used with histology 9731/3.
These plasmacytomas are localized plasma cell neoplasms that arise in tissues other than bone. Approximately 80% of extramedullary plasmacytomas occur in the upper respiratory tract including the oropharynx, nasopharynx, sinuses, and larynx. They may occur in numerous other sites including the gastrointestinal tract, lymph nodes, bladder, CNS, breast, thyroid, testis, parotid, and skin. 15% of upper respiratory plasmacytomas spread to the cervical lymph nodes. Radiology and bone marrow examination show no evidence of involvement. Do not code plasma cell myeloma/multiple myeloma (9732/3) just because there are multiple extraosseous plasmacytomas.
FISH and immunohistochemistry help to differentiate these lesions from MALT lymphoma.
Definitive Diagnostic Methods
Ig clonal rearrangements, complex karyotypes with multiple chromosomal gains/losses; also translocations, deletions, mutations