Immunohistochemical analysis of 36 cases of chondroblastomas: A single institutional experience.

Chondroblastoma is a relatively uncommon, primary benign bone tumor, frequently identified in young individuals. Despite its classical radiologic and histopathological features, at times, it is fraught with a diagnostic challenge, especially differentiating it from a giant cell tumor of bone (GCTB); an osteosarcoma and a chondrosarcoma. Lately, few studies have shown the diagnostic utility of immunohistochemical (IHC) expression DOG1 antibody in chondroblastomas. The present study was undertaken to evaluate IHC expression of S100 protein, DOG1 and p63 in 36 chondroblastomas. From January 2013 to July 2019 (6-year duration), 106 chondroblastomas were diagnosed, with IHC staining performed in 36 cases. Conventional Hematoxylin and Eosin stained microsections and IHC stained sections were reviewed in 36 cases. IHC staining of p63 (intranuclear), S100 protein (nuclear and cytoplasmic) and DOG1 (cytoplasmic membranous) was recorded in various cases. Seventy-four tumors occurred in males and 32 in females, within age-range of 7-55 years (average = 18.6), frequently in tibia (33/106; 31.1%), followed by femur (26, 24.5%) humerus (22, 20.7%), calcaneum (5) and scapula (4). IHC staining for S100P was positive in 33/36cases (91.7%); DOG1 in 16/19 (84.2%) cases and p63 in 10/15cases (66.6%). DOG1 immunostaining was negative in 25 various other tumors. Sensitivity and specificity for S100P, DOG1and p63 in chondroblastomas was (91.6%, 59.3%); (84.2%, 100%) and (66.6%, 46.6%), respectively. P63 was positively expressed in 15/27 (55.5%) GCTBs. S100 protein and DOG1 can be utilized for a confirmatory diagnosis of a chondroblastoma, especially for differentiating it from its other differentials, such as GCTB, in view of certain associated therapeutic implications. P63 is not useful in that scenario.