Plasmocytomas of the temporal bone are extremely rare. In the extensive review of world medical literature I have found only 2 other cases reported. One was that of Cappell and Mathers,1 who stated in 1934 that their case of plasmocytoma of the petrous bone, proved by necropsy, was the first reported. The second case was cited by Fowler2 from Neumann, who described a case of an involvement of the petrous bone, but from the description it was difficult to determine whether the tumor spread throughout the petrous bone or was confined solely to the mastoid process.
These plasma cell tumors, or plasmocytomas, may be medullary, when they arise from the bone marrow, or extramedullary, when they develop from other sites, such as the nasal mucosa, conjunctiva, lymph nodes and ovaries. When a tumor arises either in the tonsil or in the humerus, it is not difficult to identify its source
GROS JC. PLASMOCYTOMA OF TEMPORAL BONE. Arch Otolaryngol. 1945;42(3):188–190. doi:10.1001/archotol.1945.00680040248007