The article by Nishikubo et al.1 on the interesting subject of multiple primary malignant tumors (MPMTs) reviewed 186 cases of renal cell carcinoma (RCC) and 405 cases of lymphoid malignancies; the authors described eight patients with RCC in association with metachronous lymphoid malignancies. They noted that the incidence of this association in the same patient is higher than anticipated in the general population and discussed two possible causative factors: 1) a common genetic mutation, and 2) an immunomodulatory role of the first malignancy predisposing to the second. (The tumors did not occur simultaneously in any of these patients.) Recently, we observed in a white man, age 66 years, an RCC and synchronous bilateral lymphomas of the testes. Since 1989 he received procainamide for atrial fibrillation. In 1976 he had a carcinoma in situ of the floor of the mouth and in 1989 a squamous cell carcinoma of the roof of the mouth. He underwent bilateral orchiectomy in July 1996 for orange-size testicular tumors, present for 1 week. The microscopic diagnosis was large cell, noncleaved, diffuse malignant lymphoma, virtually replacing both testes. A month later, an ultrasound study revealed a 7 × 7 cm tumor in the lower pole of the left kidney. Microscopic examination of the resected kidney disclosed an encapsulated RCC 7 cm in diameter and microscopic malignant lymphoma in the soft tissues of the hilum. The patient received chemotherapy. He had 7 brothers and 3 sisters: 3 brothers died of cancer (esophageal, lung, and unknown) in their seventies; a sister died of breast carcinoma at age 49 years. The case was unique because the lymphoma involved both testes simultaneously and the lymphomas were synchronous with the RCC. Lymphoma of the testis is the most common testicular neoplasm in men over age 60 years. It is usually a secondary manifestation of systemic disease. Primary synchronous bilateral malignant lymphoma of the testes is a rare phenomenon2; we reported such a case in 1994.3 The occurrence of primary synchronous, bilateral, malignant lymphoma of the testes with RCC is rarer still. Because of the synchronous occurrence of the tumors in our case, the second possibility entertained by Nishikubo et al. becomes weaker, and the first possibility remains the only one that may explain the pathogenetic link. For decades we have been following with interest the involvement of urinary tract cancers and especially RCC in MPMT. As early as 1954, Haddad4 reported a case of a primary transitional cell carcinoma of the right ureter in association with an adenocarcinoma of the colon in a female patient, age 66 years. In 1984, we reported among 2005 patients with malignancies, proven at autopsy, 93 patients (4.6%) as having MPMTs in two different organs; the MPMTs had component of non-Hodgkin's lymphoma in 7 cases, RCC in 6 cases, and prostate carcinoma in 2 cases.5, 6 However, not a single patient harbored RCC and a lymphatic malignancy synchronously or metachronously. In 1996, Haddad reported one patient with adenocarcinoma of the prostate associated with small cell carcinoma of the lung and another patient with transitional cell carcinoma of the bladder associated with chronic lymphatic leukemia.7 Of our recent 31,477 surgical specimens (1991-1996), we found 95 malignant lymphomas (including Hodgkin's disease) and 30 RCCs; the patient described above was the only one suffering from both malignant lymphoma and RCC. Recently, we also observed at autopsy of a white man, age 78 years, a localized, 5 cm in diameter, clear cell carcinoma (Grade 1) of the right kidney associated with a synchronous, widely metastatic, poorly differentiated hepatocellular carcinoma. We agree with Nishikubo et al. that further studies are warranted on this interesting subject. Ifat A. Shah M.D.*, Farid S. Haddad M.D.*, Osama S. Gani M.D.*, C. Cecilie Alfsen M.D.*