Malignant transformation of osteoblastoma: study using image analysis microdensitometry.

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Abstract
AIM--To determine if the malignant transformation, as perceived histologically, in a case of osteoblastoma from the right femur, was also expressed as a quantitative change in nuclear DNA during tumour progression over five months. METHODS--Nuclear DNA microdensitometry by computer image analysis was used to acquire relative DNA distribution patterns. Tissue had been removed on four separate occasions from a lesion in the right femur of an 18 year old man. Retrospective DNA analysis was performed on formalin fixed, paraffin wax-embedded tissue. RESULTS--The DNA profile of the initial biopsy specimen, which was histologically diagnosed as osteoblastoma, was euploid with a near diploid (2c) modal DNA. The second biopsy specimen taken one month later also resembled osteoblastoma but showed an aneuploid DNA profile with a diploid modal DNA and some nuclei with ploidy greater than 5c. The third biopsy specimen taken four months later showed histological evidence of osteosarcoma and a near pentaploid (5c) modal DNA with large number of nuclei exceeding 5c. CONCLUSIONS--DNA microdensitometry confirmed the initial and final diagnosis. The technique also seems to be capable of detecting aneuploidy before malignancy is morphologically evident.