An unusual initial presentation of a lung carcinoma with multiple extensive bone metastasis – a diagnostic dilemma

Background: Bone is a common metastatic site of primary lung carcinoma. But bone metastasis being the initial presentation of primary lung malignancy is rare and only a few cases are reported in literature. We report a case of a primary lung cancer with extensive bone metastasis to skull and long bones, with no clinically or radiologically evident primary tumor. Case presentation: A 45 years old male presented with left lower limb pain for two weeks duration. He also had progressively enlarging two bony lumps on the scalp for six months. He had no other symptoms on inquiry. Examination revealed two large protruding bony lumps on scalp, on posterior vertex and on the left forehead. Respiratory system examination was normal. Skeletal survey showed lytic lesions in right tibia and left humerus with two large bone lesions in the skull extending in to brain matter evident on Contrast CT brain. Chest radiograph revealed no significant lesions. First biopsy of posterior scalp lesion was inconclusive. On further imaging, the contrast enhanced CT chest revealed a small left lung opacity suggestive of bronchogenic carcinoma. Deep FNAC of the posterior scalp lump revealed squamous cell origin, possible metastasis from primary lung carcinoma. Conclusion: Our case highlights, that a primary lung carcinoma without clinical or basic radiological evidence can present with large multiple extensive bony metastasis, where early advanced imaging is important to prevent diagnostic dilemmas and therapeutic delay.