Metastasis - Detected On Radiology

A 58 years old male came to his physician complaining of chest pain  for about 6 months. The pain was initially mild but now has gradually increased in severity. The patient mentions feeling tired all the time with no energy and unintentional weight loss.
He was sent for a chest X ray which is shown below:

X-ray chest shows a large (8 × 6 cm) well-defined mass lesion abutting the left lower chest wall with broad base towards the chest wall with partial destruction of lateral aspect of 4th rib on the left.

It was suspected to be a malignant lesion. CT chest was advised which is shown below:

Contrast CT chest (Figs A to D) was done which shows moderately enhancing metastatic bone lesion which is rounded and well-defined having a large soft tissue component from the left 4th rib, and right 10th rib (Figs B and C) laterally, the ribs are partially destroyed, few small scattered calcific densities are seen in the lesions. There is a single iso to hypodense lesion seen in liver measuring 5 × 4 cm. The lesion shows moderate heterogeneous post-contrast enhancement (Fig. D).

Diagnosis: Metastasis to ribs and liver

Case Discussion: Primary tumors which originate in other organs and involve the skeletal structures of the body either by hematogenous, lymphatic route or by direct invasion are called metastasis.
Metastases are generally multiple commonly found in the axial skeleton and sites of residual red marrow.
The common sites are vertebrae, pelvic bones, proximal femur and humerus, skull and ribs. It is unusual for metastasis to involve bones distal to the elbows or knees.
Osteolysis within the thoracic skeleton is frequent and is usually as a result of metastases. Other causes of osteolysis are enchondroma, eosinophilic granuloma or multiple myeloma.
In addition to destructive processes, degenerative processes involving sclerosis and osteophyte formation of bone must be differentiated from osteosclerotic metastases, which are usually from carcinoma prostate.
The common primary neoplasm which spread to bones is from breast, lungs, prostate, kidney and thyroid.
Occult primary is a primary malignancy in which there are no localizing signs suggestive of the site of primary tumor and has not been detected by any of the available investigative protocols. However, the metastatic lesions have been detected on clinical, radiological and biomedical parameters. Histopathology may suggest the likely site of primary.