Immunoreactivity of CD99 in Non-Hodgkin's Lymphoma: Unexpected Frequent Expression in ALK-positive Anaplastic Large Cell Lymphoma

To verify the spectrum of CD99-expressing lymphoid malignancy, an immunohistochemical study for CD99 was carried out in 182 cases of non-Hodgkin's lymphoma, including 21 lymphoblastic lymphomas, 11 small lymphocytic lymphomas, 9 mantle cell lymphomas, 12 follicular lymphomas, 37 diffuse large B cell lymphomas, 18 Burkitt's lymphomas, 28 NK/T-cell lymphomas, 8 angioimmunoblastic T-cell lymphomas, 23 peripheral T-cell lymphomas, unspecified, and 15 systemic anaplastic large cell lymphomas. CD99 was positive in all T-lymphoblastic lymphomas and in 60% of B-lymphoblastic lymphomas. Majority of T and NK cell lymphomas were negative for CD99, except anaplastic large cell lymphomas (ALCLs). Eight of 15 cases (54%) of ALCLs reacted with anti CD99 antibody. Seven of 10 (70%) ALK positive ALCLs expressed CD99, whereas only 1 of 5 (20%) ALK negative ALCLs were positive. Of the mature B-cell lymphomas, 5.4% (2/37) of diffuse large B cell lymphomas and 11.1% (2/18) of Burkitt's lymphomas expressed CD99. In conclusion, CD99 is infrequently expressed in mature B and T cell lymphomas, except ALK-positive ALCL. High expression of CD99 in ALK-positive ALCL is unexpected finding and its biologic and clinical significances have yet to be clarified.

A Case of Primary Gastric CD30-Positive Anaplastic Large-Cell Lymphoma

Gastric CD30-positive anaplastic large-cell lymphoma is a very rare disease. It is sometimes difficult to distinguish it from undifferentiated carcinoma, sarcoma and so on. We report here on a case of primary gastric anaplastic large-cell lymphoma. A 50-yr-old woman complained of epigastric pain and severe chest pain for 1 week. The gastroendoscopic examination revealed geographic mucosal irregularities with shallow ulceration at the antrum. She underwent a total gastrectomy. The gross finding of the resected stomach was an 8 x 4.5 cm sized ulceroinfiltrative lesion at the pyloric antrum along the lesser curvature. The microscopic examination revealed diffuse and solid proliferations of large atypical cells with pleomorphic nuclei. Immunohistochemically, the tumor cells were positive for CD30, vimentin and CD3, and this was a finding compatible with anaplastic large-cell lymphoma. To the best of our knowledge, this is the first such reported case in Korea.