A 49-year-old female with multiple endocrine neoplasia (MEN) type 1 associated with malignant lymphoma, lipoma, functioning adenomatous goiter, non-functioning adrenal tumor, polyneuropathy, postoperative primary hyperparathyroidism, and hepatitis B virus was a human T lymphotropic virus type 1 (HTLV-1) carrier. She underwent parathyroidectomy for primary hyperparathyroidism at age 44. At age 49, examinations of the enlarged para-aortic lymph nodes revealed diffuse small non-cleaved B cell lymphoma in stage II, and other various complications were also found. Multiple tumorigenetic factors were considered to be involved in the present case.