Chondrolipoma in pelvic cavity in 55-year-old man.
A, B. Transverse (A) and coronal (B) CT images show 8 cm, well-defined mass occupying left side of presacral space of pelvic cavity. Mass seems to have long stalk arising from left gluteus medius muscle. Stalk traverses along surface of left iliac bone, and further passes through left sciatic foramen, and finally connects with mass. Mass is mainly composed of fatty tissue and calcification. Note that calcifications in mass are located peripherally in linear and rosary pattern, with most of stalk becoming calcified. There are some focal areas of intermediate attenuation (arrows) between fat tissue and calcification, which corresponds to chondroid tissue histologically.
C-E. Plain T1-weighted transverse (C), T2-weighted transverse (D), T2-weighted coronal (E) MR images without fat suppression show same mass mainly composed of hyperintense areas and signal void areas on both T1- and T2-weighted images which represent fatty tissue and calcification, respectively. Also seen are focal areas of intermediate signal intensity (arrows), which corresponded to chondroid tissue, as seen on CT images.
F, G. Gadolinium-enhanced T1-weighted sagittal MR images without fat suppression, obtained 30 seconds (F) and 3 minutes (G) after contrast injection, show same fatty mass with extensive calcifications. Note focal areas of intermediate signal intensity around calcifications (arrows) in F become isointense as with surrounding fatty tissue in G. This represents delayed enhancement.
H. Cut surface of resected specimen shows 13 cm, yellowish mass with whitish area in upper portion, which inidcates that this mass is composed of yellowish fatty tissue and whitish calcification.
I. Photomicrograph of resected specimen indicates mature, fatty (black arrows), chondroid (white arrows), and fibrous (white arrowheads) tissues (Hematoxylin & Eosin staining, ×100). These findings are consistent with chondrolipoma.