Cortical metastasis - unusual type of skeletal metastatic disease

Clinical History

A 56 year-old male smoker patient with verified non-small cell lung cancer (NSCLC) was complaining of pain in the upper part of the thigh.

Imaging Findings

Whole body planar bone scan and SPECT/CT of the area from calvaria to proximal one-third of the shin were performed 2 hours after intravenous injection of 740 MBq Tc99m-MDP. Planar bone scan showed elongated lesion of increased radiotracer uptake in proximal one-third diaphysis of the right femur with central well-defined photopenic defect at posterior projection. Additionally, a heterogeneous area of increased radiotracer uptake was detected in the supraspinatus part of the left scapula. Other areas of abnormal radiotracer uptake, which could be evidence of tumour lesion were not detected. SPECT/CT showed osteolytic lesions with full thickness cortex destruction, extraosseous soft tissue component propagation, in the femur with moderate intramedullary spread, periosteal reaction in the form of “Codman triangle” and increased radiotracer uptake at the periphery of bone defect. Morphological verification, including IHC test, was performed. According to IHC findings, the identified lesion presented bronchogenic carcinoma metastasis.

Discussion

Bone is one of the most common sites of distant metastases from cancer. Breast cancer, prostate cancer, lung cancer and renal cell carcinoma are the site of origin of 80% bone metastases [1]. Lung cancer is the third most frequent site of origin of skeletal metastases, after breast and prostate cancer. Bone is a common site of metastatic deposits from NSCLC (20–40%) [2]. Spine is the most frequent site of bone metastases. Other common sites are pelvis, proximal humerus, ribs, skull and 6% in femur [3].
Isolated cortex destruction is not a typical pattern of metastatic bone lesions. It is rarely mentioned in medical literature and reveals itself in solitary or multiple lesions of long bones, which can be the first indication of a malignant process [4]. Primaries in lung, breast, kidney and pancreas are causes of cortical metastases [5]. Some authors consider this metastatic pattern as typical for bronchogenic carcinoma, pointing at the typical localization at femoral diaphysis and defining 4 types of lesion: small cortical destruction-"cookie-bite" or "cookie-cutter" lesions, large osteolytic cortical lesions, saucerized intracortical lesions with well-defined periosteal reaction, and lesions with predominant cortical destruction extending into the soft tissue as well as the medullary cavity [6, 7]. A group of autors reported a case of a solitary femur metastatic cortex destruction lesion of a patient with NSCLC [8]. They had analog results of the planar bone scan and SPECT/CT. Pathogenesis of this type of metastatic lesion is not clearly defined. Considering the arterial blood supply of the cortex, which originates from a periosteum vasculature communicating with the bone nutrient artery basin, an isolated cortex lesion may take place, beside a secondary cortex involvement at a primary marrow lesion.
Bone metastases may be the first manifestation of cancer. It is necessary to keep in mind that there are different types of metastatic bone lesions, including cortex metastases.

Differential Diagnosis List

Final Diagnosis

Femoral cortical metastasis from NSCLC.

URL:	https://www.eurorad.org/case/13056
DOI:	10.1594/EURORAD/CASE.13056
ISSN:	1563-4086