Primary salivary gland lymphoma: a clinicopathologic study of 23 cases in Taiwan

Twenty-three patients with primary salivary gland lymphoma were diagnosed between 1990 and 2001. The sites of involvement were the parotid gland in 13, the submandibular gland in 9 and the minor salivary gland in 1. The sites of lymphoma involvement beyond the salivary glands were the cervical lymph nodes in 7, bone marrow in 3, the axillary lymph nodes in 3, the nasopharynx in 2, the abdominal lymph nodes in 2, the palate, the subconjunctiva, and the spleen in 1 each patient. Histologically, 19 patients had lymphomas of mucosa-associated lymphoid tissue (MALT) with myoepithelial sialadenitis in 13, 3 patients had diffuse large cell lymphomas and 1 had follicular lymphoma. Six patients were in stage I, 4 in II, 1 in III and 12 in IV. Eight of 23 patients (35%) had autoimmune diseases before or after the diagnosis of NHL and all suffered from MALT lymphoma. Four patients with parotid MALT lymphoma had primary or secondary Sjogren's syndrome. One each patient suffered from hyperthyroidism, systemic lupus erythematosus, membranoproliferative glomerulonephritis and cryoglobulinemia, respectively. All the 6 stage I patients had achieved complete remission (CR) without relapses 17-84 months (median 44 months) after treatment. Excluding a stage IV patient with follicular lymphoma who died at 3.5 months without treatment, CR was achieved in all of the remaining 16 patients. However, a high relapse rate (9/16, 56%) was noted in stage II-IV patients. These patients tended to relapse in the original sites, but achieved CR again after chemotherapy or radiotherapy. One patient with MALT lymphoma developed histologic transformation into diffuse large lymphoma during relapse and died of refractory disease. Overall, only 2 patients succumbed. The overall survival and relapse-free survival rates at 5 years were 94.7 and 51.4%, respectively. Thus, salivary gland lymphoma proved to be an indolent disease.