METASTATIC MELANOMA - CORRELATION OF MRI CHARACTERISTICS AND HISTOPATHOLOGY

To correlate the findings on MRI with histopathology of metastatic mel anoma, MRI was performed on 29 patients with 36 lesions, using spin-ec ho and inversion recovery sequences. Histopathologic examination of le sions was performed within 4 weeks of imaging. Lesions were categorize d according to cell type and were also evaluated for the presence and extent of melanin, iron, and necrosis, These data were then correlated with the signal intensities of the lesions. Enhancement of lesions af ter injection of intravenous gadolinium was calculated and correlated to vascularity of the tumor. Melanin was present more frequently in le sions appearing hyperintense or with mixed signal intensity (12/15) th an in those appearing hypo- or isointense (6/21) on the T1-weighted se quence. This trend was significant (P=.013), Also, more lesions appear ing mixed, ie, having both hypo- and hyperintense components, containe d melanin (15/23), as opposed to lesions that appeared to be only hype rintense (3/13) on the STIR sequence, There was no clear association b etween signal intensity and melanin content on the T2-weighted sequenc e. There was no significant association between the signal intensities on the MR images and the iron content, tumor size, or tumor cell type of these lesions, There was no clear association between enhancement after gadolinium injection and vascularity, as assessed by histology. The authors concluded in this study that T1 shortening and hypointensi ty on the STIR sequence seen in patients with metastatic melanoma are most closely related to the melanin content of the tumor.