[58] Immunohistochemical Comparative Study of Chondromyxoid Fibroma, Chondroblastoma and Chondrosarcoma, Using Sox9, p63 and CAM 5.2

E Konishi, Y Nakashima, Y Iwasa, A Yanagisawa. Kyoto Prefectural University of Medicine, Kyoto, Japan; Kyoto University Hospital, Kyoto, Japan; National Hospital Organization Osaka Medical Center, Osaka, Japan

Background: Recently, some antibodies are thought to be useful makers for differential diagnosis of the bone tumors. Sox9, an essential regulator of chondrogenesis can immunohistochemically distinguish mononuclear cells of mesenchymal chondrosarcoma from other small blue round cell tumors, including Ewing sarcoma/PNET. Some cytokeratins, such as CK8, CK18, and CK20 are expressed in chondroblastoma (CB) but not in chondromyxoid fibroma (CMF). Furthermore, p63 can differentiate mononuclear cells in giant cell tumor from those in other lesions, such as CB, brown tumor, etc. To elucidate the characteristics of CMF, CB and conventional chondrosarcoma (CS), we performed immunohistochemical analysis of Sox9, S-100, type II collagen, CD10, p63, and CAM5.2 (mixture of CK8+CK18).
Design: Ten CMFs, six CBs and eight CSs were studied. Immunohistochemical expression of Sox9, S-100, type II collagen, CD10, p63, and CAM5.2 was analyzed in each case. All antibodies were commercially available.
Results: Positivity of immunostaining is shown in the Table.

Results of Immunostaining (positive number)

	Sox9	S-100	type II collagen	CD10	p63	CAM5.2
CMF (n=10)	10/10	5/10	7/10	3/10	6/10	1/10
CB (n=6)	6/6	6/6	4/6	0/6	6/6	6/6
CS (n=8)	8/8	8/8	8/8	0/6*	0/8	0/8

*Some specimens floated off the glass slides. :p<0.05, , :p<0.01

Sox9 was detectable in the nuclei of CMFs, CBs and CSs, even in only focal area. Positive cells were usually in the myxoid or chondroid matrix. S-100 was found in the nuclei and/or cytoplasms of CBs and CSs. Half cases of CMFs were positive for S-100. Myxoid or chondroid matrix of most CMFs, CBs, and CSs was positive for type II collagen, even in focal area. CD10 was occasionally positive in the tumor cells at the periphery of the chondromyxoid lobules of CMFs, however, was negative in those of CBs and CSs. p63 was positive in the nuclei of CBs and sometimes positive in CMFs but not in CSs. CAM 5.2 was positive in all CBs, but in only one CMF. It was negative in CSs.
Conclusions: 1) CMF was verified as chondrogenic tumor in terms of the positivity of Sox9, as well as type II collagen. 2) CMF occasionally contained CD10 positive tumor cells, but CB and CS did not. 3) p63 might be a useful marker to distinguish CS from CB and CMF. 4) CAM5.2 could differentiate CB from CMF and CS.
Category: Bone & Soft Tissue

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 20, Tuesday Morning