PRIMARY CARCINOID OF THE KIDNEY - IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL STUDIES OF 5 PATIENTS

Background. Primary carcinoid tumor of the kidney is rare; only 18 pat ients have been reported. Because of the rarity of the lesion, its pro gnosis and clinicopathologic features are not well characterized, and its histogenesis is unknown. Methods. Clinicopathologic, immunohistoch emical, and ultrastructural studies were performed on five patients wi th primary carcinoid tumor of the kidney. Results. Age of the patients ranged from 42 to 63 years, with a mean of 53.2 years. Only one patie nt had a carcinoid syndrome. Three were men, and two were women. In ea ch patient, the tumor was solitary and confined to the kidney. All tum ors had histologic features identical to those of carcinoid tumors aff ecting other sites. The cytoplasmic granules of the tumor cells were r eactive with Grimelius stain in all patients. Alt tumors also were imm unoreactive for keratin, neuron-specific enolase, and chromogranin, bu t only two patients had tumors that reacted for serotonin, pancreatic polypeptide, and vasoactive intestinal polypeptide. Ultrastructural st udies showed numerous intracytoplasmic neuroendocrine granules in four tumors. One patient had Robson Stage I cancer, and two each had Stage II and IV cancer. The two patients with Stage IV tumor died of diseas e at 36 months and 28 months after diagnosis; one patient with Stage I I carcinoid is alive without clinical evidence of residual disease 8 y ears after control of metastases; the other patient with Stage II and the patient with Stage I cancer are alive and well without evidence of disease at 36 months, and 2 months, respectively. Conclusion. Tumor s tage at presentation appears to be the most important factor in determ ining outcome. The number of mitoses and degree of cellular atypia app ear to be important pathologic parameters in predicting prognosis, des pite the limited number of patients reported in this report.