Clinical history: 83 year old patient presented with melena. A Forrest grade 3 ulcer was noted in the stomach during endoscopy and was biopsied.
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Discussion and answers
The lamina propria of the gastric mucosa in this specimen is infiltrated with cells that have increased nuclear to cytoplasmic ratio and pleomorphic, large, hyperchromatic nuclei. The cells have abundant amphophilic cytoplasm and some show plasmacytoid features with eccentric nuclei. Some of the cells have multiple, prominent nucleoli. They are not seen to form any glandular structures and do not have intercellular adhesions. There are 2-4 mitoses per high power field. Occasional lymphocytes are seen between these tumor cells. There are no areas of necrosis.
Immunohistochemical staining showed that the cells are positive for CD138, EMA, MUM1 and bcl2, but negative for S100, HMB45, CK7, CK20, AE1/3, CD3, CD5, CD10, CD20, CD23, bcl6 and p53. The cells show kappa light chain restriction, and are negative for EBER. Ki67 staining shows proliferative activity in more than 90% of the cells.
Multiple myeloma with plasmablastic features
Considering the unusual distribution, the cytologic and immunological features plasmablastic lymphoma was considered in this case. These are an aggressive group of B-cell neoplasms composed of immunoblastic, large, transformed lymphoid cells with absent or weak expression of CD45 and CD20 but positive staining for plasma cell markers CD38 and CD138. They tend to occur in immunocompromised and HIV positive patients. Most cases, especially in HIV negative patients, are EBV+. There is considerable overlap with extramedullary 'plasmablastic' myelomas. In the current case the patient also had a previous history of bony lesions and a diagnosis of multiple myeloma with plasmablastic features in a previous lymph node biopsy, which further supported the diagnosis.