Hemosiderin deposition in papillary renal cell carcinoma and its potential to mask enhancement on MRI: analysis of 110 cases

Abstract

Objectives To evaluate the relationship between imperceptible T1 enhancement of papillary renal cell carcinoma (pRCC) on MR and intratumoral hemosiderin deposition. Methods One hundred ten pRCCs (<= 7 cm) were evaluated by MR with in- and opposed-phase spoiled gradient echo (GRE) and T1-weighted spoiled GRE with fat suppression before and after contrast. Hemosiderin deposition was assessed by SI(index)and D(index)on in- and opposed-phase images. SI(index)and D(index)are calculated as (SIin- SIopp)/(SIin) x 100, where SI(in)and SI(opp)are tumor signal intensities on in- and opposed-phase images and (D-in)/(D-opp), where D(in)and D(opp)are tumor diameters on in- and opposed-phase images, respectively. The degree of tumor enhancement was classified as grade 1 (no), grade 2 (subtle), or grade 3 (definite). Tumor enhancement on CT was assessed when available. Results Five (5%), 10 (9%), and 95 (86%) tumors were categorized as grades 1, 2, and 3 enhancement, respectively. The mean SI(index)was - 33.9, - 25.3, and 1.00, whereas the mean D(index)was 1.26, 1.05, and 1.00 in tumors with grades 1, 2, and 3 enhancement, respectively. Tumors with grade 1 enhancement had significantly lower SIindex(p= 0.001) and higher D-index(p= 0.005) than those with grade 3 enhancement. Among six tumors with grade 1 or 2 enhancement and available CT, four tumors showed > 20 HU enhancement. Conclusions pRCC with no subjective enhancement on contrast-enhanced MR showed hemosiderin deposition evident by lower SI(index)and higher D-index. Hemosiderin deposition might mask the tumor enhancement on MR.