A middle-aged Japanese woman visited the Orthopedics Department of Nihon University Nerima Hikarigaoka Hospital complaining of
pain in the left hip joint that had started approximately 8 months earlier. Following several examinations, including imaging diagnoses, an incisional biopsy demonstrated a malignant acetabular bone
tumor, which was removed and examined by a quick-freezing and deep-etching (QF-DE) method, conventional electron microscopy, and light microscopy. Histologically, the
tumor was a
chondrosarcoma with marked myxoid changes. An interesting extracellular matrix was observed by the QF-DE method. The myxoid area consisted of a fine meshwork of
proteoglycans (PG) without obvious
aggrecans, which resembled that of PG usually present in the pericellular matrix of normal cartilage. Thin
collagen fibrils with pleated surface structures of regular periodicity were also seen, which were sparsely distributed in wide areas except for the pericellular matrix. These
collagen fibrils were of the type that are mainly located in the pericellular side of the territorial matrix in normal cartilage. A myxoid matrix consisting of thin
collagen fibrils on the background of pericellular type PG suggested that the myxoid matrix in the
chondrosarcoma resembled those of the pericellular and pericellular sides of the territorial matrices in normal cartilage.