Cortical metastatic lesions of the appendicular skeleton from tumors of known primary origin.

Background And Objectives: Metastatic disease represents the most common neoplastic process involving bone. Recently, a small subset of cortical based metastatic lesions has been identified. We attempted to delineate the incidence, origin, location, and possible significance of these lesions within an orthopaedic patient population.

Methods: A chart and radiographic review of patients treated for metastatic disease to bone over a 17-year period was performed. Inclusion criteria for lesions were as follows: 1) an appendicular skeletal site, 2) histopathologic confirmation of origin, and 3) presence within a patient diagnosed with a single, known neoplastic process. The lesions were classified as either cortical or medullary based.

Results: Eighty-three lesions (70 patients) satisfied inclusion criteria. Most lesions were of pulmonary (26), breast (22), renal (16), or prostatic (8) tumor origin. Eighteen lesions (22%) from 15 patients were identified as cortical and represented initial presentation in 7 patients. These lesions were of pulmonary (11), renal (5), and breast (2) tumor origin.

Conclusions: Cortical based metastases within the appendicular skeleton may occur more frequently than previously expected. While tumors of pulmonary and renal origin accounted for 42 of the 83 (51%) appendicular lesions, they were responsible for 16 of the 18 (89%) cortical metastases. This preponderance of pulmonary and renal metastases to the cortex is consistent with previously published reports. Our findings may be of value when diagnosing and treating patients whose initial presentation is a cortically based lesion.