The detection of cytokeratin-positive cells in bone marrow of patients with various carcinomas is considered an adverse marker. To establish a routine diagnostic procedure to detect these cells in patients with urologic carcinoma, we evaluated different immunocytological techniques in parallel. The study included 50 patients with urologic carcinoma (16 with metastatic disease) and 10 healthy volunteers. Bone marrow was aspirated from the iliac crest; after density centrifugation, cytocentrifuged specimens were stained according to optimized modifications of conventional immunocytologic techniques. Overall only 3% of patients with locally restricted carcinoma and only 19% with metastatic disease showed cytokeratin-positive bone marrow cells. Nonspecific labeling of bone marrow cells in the immunoglobulin isotype controls was a major problem, demonstrating the need for numerous detailed controls. If all nonspecific reactions were excluded, up to 20% of the healthy controls yielded positive results as well. The presence of cytokeratin-positive cells in bone marrow aspirates shows only slight correlation with systemic metastasis. The biologic and clinical relevance of this immunocytologic marker must be judged cautiously.

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