Hereditary multiple exostoses with malignant transformation

Case contributed by Dr Matt Skalski


Pelvic pain, difficulty with urination and defecation.

Patient Data

Age: 35 years old
Gender: Male

There is a large mass within the pelvic outlet which demostrates a fine ring and arc pattern pattern of calcification. The mass occupies the majority of the diameter of the pelvic basin. 

Note that there are multiple sessile osseous escresences along the proximal right femur including the proximal right femoral neck (Brahman bull appearance) and metaphysis, as well as pedunculated excressences at the lesser trochanter and femoral neck on the left, and anterolateral ilium on the right. These excressences demonstrate medullary continuity with their parent site. 

The lungs show no evidence of metastatic involvement. Note the multiple sessile osteochondromas along the proxmal right humerus, as well as one partially visible sessile osteochondroma on the left humerus. Other osteochondromas are noted at the right clavicle and right scapula. 

The mass lesion is again identified within the pelvis, and appears to originate from an osteochondroma at the posterior aspect of the right superior pubic ramus. The mass lesion measures 15 x 9.4 x 14 cm in AP, transverse, and superioinferior dimensions, respectively. The mass demonstrates a rings-and-arc pattern of calcifcation, suggesting a chondroid matrix. 

The mass displaces the urinary bladder, which is decompressed with a Foley catheter present within the bladder. The mass also has a mass effect on the rectum, displacing it posteriorly and to the left.

The mass lesion does not demonstrate any vessel or neurovascular bundle encasement. No additional mass lesions are identified.

Case Discussion

Malignant degeneration of an osteochondroma in patient's with hereditary multiple exostoses is the most feared complication of the disease. When osteochondromas become malignant, the cartilaginous cap which transforms most often into a chondrosarcoma, which is the case in this patient. This patient also reported that he had multiple family members with bony bumps, illustrating the autosomal dominant inheritance pattern of the disease.

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Case information

rID: 26801
Published: 8th Jan 2014
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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