Intermediate grade osteosarcoma and chondrosarcoma arising in an osteochondroma. A case report of a patient with hereditary multiple exostoses

Abstract

A 40 year old man with hereditary multiple exostoses (HME), affecting predominantly his left proximal tibia, distal femur, and proximal femur, underwent resection of an osteochondroma near the trochanter major of his left proximal femur because of malignant transformation of the cartilaginous cap towards secondary peripheral chondrosarcoma. The patient had a history of a papillary thyroid carcinoma four years previously. At examination of the resected specimen, a third malignant tumour, an intermediate grade osteosarcoma (grade II/IV), was found in the osseous stalk of the osteochondroma. Although no mutations were found in the EXT1 and EXT2 genes, the genes involved in HME, or in exons 5-8 of the p53 gene, the development of three malignancies before the age of 40 suggests that this patient is genetically prone to malignant transformation.

Figure 1

(A) Light micrograph of the papillary thyroid carcinoma that was removed four years previously. (B) Light micrograph of the cartilaginous cap, displaying widely spaced, pronounced atypical, binucleated chondrocytes. (C) Light micrograph of a histologically distinct area present within the stalk of the tumour. This area is composed of an admixture of moderately pleomorphic tumour cells with the formation of a trabecular deposited osteoid. Note the presence of a mitotic figure.

Figure 2

(A) An anterior-posterior radiograph of the left femur, taken three years before presentation (at age 37), displays ring-like and amorphous calcifications in the soft tissues. The normal cortex is continuous with the lesion. (B) Bone scintigraphy at presentation at age 40 displays focally increased accumulation of radiotracer. This was found predominantly at the site of the grade II osteosarcoma, located in the stalk of the osteochondroma. (C) On T1 weighted images after intravenous injection of gadolineum–DTPA a uniform septal and nodular enhancement of the tumour is seen.

Figure 3

The chondrosarcoma is negative for p53 (A), whereas the grade II osteosarcoma shows p53 overexpression (B).