Malignant transformation of osteoblastoma: study using image analysis microdensitometry.

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.