A B-cell lymphoma diagnosed in "floater" tissue: implications of the diagnosis and resolution of a laboratory error.

Contamination of a paraffin-embedded tissue block with another patient's tissue can lead to an incorrect diagnosis. We report the use of short tandem repeats for the analysis of DNA extracted from microdissected tissue from unstained slides prepared from a decalcified block from a 33-year-old woman who was previously diagnosed with a low-grade B-cell lymphoma. This diagnosis was based on a single fragment of tissue found among bone fragments taken during orthopedic surgery at a referring hospital. Our results confirm that the B-cell lymphoma tissue was not derived from our patient. Furthermore, we suggest that in cases for which the definitive identification of a tissue contaminant can resolve clinically, therapeutically, and prognostically significant questions, short tandem repeat analysis of DNA derived from microdissected surgical pathology samples should be considered to minimize errors and enhance the quality of care.