The result of neoplastic disease is space occupying disease. Depending on the location – different structural and functional effects and hence complications will result. Local obstruction of the airways will expectedly result in localized atelectasis Involvement of the pleura will be complicated by pleural effusion and if the pericardium is involved – pericardial effusion. If these accumulate rapidly or sizably they may respectively affect the function of the lung and heart. Acute tamponade can be life threatening.
Invasion into the lymphatics can result in lymhangitis obliterans sometimes with significant respiratory compromise and marked dyspnea. Obstruction of the SVC may result in the SVC syndrome sometimes with dramatic face swelling and discoloration.
Metastatic disease to the bone can result in pathological fracture and to the spine which at the extreme can cause significant neurological compromise and a need for urgent radiation therapy.
Another dramatic clinical presentation may be as a result of brain metastases, while bilateral adrenal metastases in the extreme can cause an Addisonian crisis.
At autopsy extra thoracic metastatic disease (and in order of diminishing frequency,) is found most commonly in patients with small cell cancer (>95%), adenocarcinoma and large cell carcinoma,(80%) and then squamous cell (>50%).
Some of the complications of local extension have been alluded to above and others occur as a result of local lymphatic extension (lymphangitis obliterans), or to distant metastases the most devastating usually being brain metastasis.
At autopsy extra thoracic metastatic disease is found most commonly in patients with small cell cancer (>95%), then adenocarcinoma and large cell carcinoma,(80%) and then
squamous cell (>50%). The adrenals, brain, liver and bone are the common sites of metastatic disease.
Paraneoplastic syndromes occur as a result of lung carcinoma but may be the presenting finding. Endocrine syndromes occur in about 10% of patients with lung carcinoma. Ectopic PTH produced by squamous cell carcinoma may produce hypercalcemia and hypophosphatemia. Small Cell carcinoma (oat cell carcinoma) may produce ectopic ADH or possibly atrial natriuretic factor resulting in hyponatremia with the syndrome of inappropriate secretion of antidiuretic hormone. SCLC may also produce ACTH resulting in electrolyte disturbances, particularly hypokalemia. Lung carcinoma can be associated with a number of paraneoplastic syndromes which elaborate hormone-like factors resulting in often clinically significant metabolic derangement.
The hormones that are commonly produced include ADH (anti diuretic hormone) and ACTH (adrenocorticotrophic hormone antidiuretic hormone), parathormone, calcitonin, gonadotropins and serotonin.
ACTH and ADH ectopic production occur predominantly with the small cell carcinomas. Carcinoid syndrome can also be associated with the small cell carcinoma, but if present is more likely to be associated with a carcinoid tumor of the bronchus. Squamous cell tumors more commonly are responsible for hypercalcemia
Autoimmune antibodies can be elicited by lung carcinoma producing a number of neuro muscular aberrancies.
Clubbing occurs in 30% of cases (usually non-small cell carcinomas) and hypertrophic pulmonary osteoarthropathy in about 5% of cases (usually adenocarcinomas)
Small cell carcinoma (oat cell cancer) is associated with neurologic-myopathic syndromes seen in about 1% of patients. All types are uncommonly associated with autoimmune induced peripheral neuropathy, cerebellar and or cortical degeneration, and polymyositis
Hypercoagulable states and other and other hematological disorders occur in about 5%, while dermatomyositis and acanthosis nigricans, and nephropathies occur in about 1% of patients.