A GP referred a 73 year old woman with a one day history of sudden painful swelling in her left arm. She was clinically well, and, apart from diffuse swelling of the whole of her left arm, physical examination was unremarkable. Doctors did a number of investigations, including a chest x ray and a computed tomography (CT) scan (figs 1- 3).

Questions:

1. What abnormality is seen in fig 1?







2. What is the investigation in fig 2? What abnormality can you see?







3. What abnormalities can you see in the CT scan (fig 3)? What is the likely diagnosis?

Answers

1. A large superior mediastinal mass causing tracheal deviation and compression.
2. A film obtained during venography of the left arm. The left subclavian vein has an irregular stricture, and the left brachiocephalic vein is occluded.
3. The CT of the chest (enhanced with intravenous contrast material) shows enlargement of the right lobe and isthmus of the thyroid gland with retrosternal extension. The retrosternal mass encases and occludes the left brachiocephalic vein. This is likely to be a thyroid malignancy invading the superior mediastinum and slowly occluding the brachio-cephalic vein.^w1-5

Discussion

The differential diagnosis of arm swelling includes myositis ossificans, bony or soft tissue tumours of the arm, haemarthrosis, post-traumatic osteodystrophy, disuse oedema, lipodystrophy, deep vein thrombosis, and secondary lymphoedema. Secondary lymphoedema may be caused by metastasis and radiotherapy to the lymph nodes; excision of the lymph nodes; or sepsis from local thrombophlebitis, a foreign body, or bacterial infection.

In this case, the speed of onset makes deep venous thrombosis the most likely cause. This condition is associated with hypercoagulability of the blood--for example, polycythaemia--changes in the vessel wall--for example, vasculitis--or, compression of the lumen of the vessel by extrinsic causes--in this case papillary carcinoma of the thyroid.

The incidence of papillary carcinoma of the thyroid is slightly higher in men. The age distribution is biphasic; the condition is more common between the ages of 30 and 40 years and 60 and 70 years. The size of the primary tumour at diagnosis varies from a small nodule to a massive tumour. In most cases, patients with papillary carcinoma will have an asymptomatic thyroid mass on examination. Large tumours can obstruct the trachea, cause paralysis of a vocal cord, or spread to distant organs and lymph nodes. Papillary carcinoma metastasises to regional lymph nodes and may recur locally after excision.

Investigation

No laboratory test can distinguish between benign and malignant lesions of the thyroid, although hyperthyroidism is rarely associated with malignancy.

Technetium scanning may show high or low uptake in the mass. If the nodule is "cold" (low technetium uptake) cancer should be highly suspected. In this case, an ultrasound guided fine needle biopsy of the thyroid gland excluded a thyroid cyst or multinodular goitre as the cause of the "cold" nodule and confirmed the diagnosis of cancer.

If on physical examination vascular invasion is suspected, arteriography and magnetic resonance angiography are valuable investigations. Computed tomography or magnetic resonance imaging can help to determine the extent of the tumour. Biopsy will confirm the histology and grade of the lesion, and the prognosis can be established using staging information from computed tomography or magnetic resonance imaging. In this case, biopsy showed papillary carcinoma of the thyroid.

Management

Papillary carcinoma of the thyroid is usually treated by surgery. The surgical approach depends on the presence and extent of local invasion of the surrounding structures. If lymph nodes are involved on preoperative imaging, they are resected at the time of surgery. Surgery is followed by radioiodine ablation treatment to prevent any residual tumour cells responding to thyroid stimulating hormone and recurring. Doctors should scan the whole body about six months after surgery and thyroid ablation. If residual disease is detected on whole body scan, doctors can give a larger dose of treatment, depending on the degree of residual uptake and assessment of the cancer risk.

As most tumours respond to thyroid stimulating hormone, levothyroxine (an articficial thyroxine analogue) suppression of thyroid stimulating hormone is the mainstay of thyroid cancer treatment. A reasonable goal is to suppress the hormone to as low as possible without subjecting the patient to unnecessary side effects from excess thyroid hormones such as atrial fibrillation, aosteopenia, anxiety, and other manifestations of thyrotoxicosis. In addition to radioiodine, doctors use external beam radiotherapy to treat specific metastatic lesions, particularly when they cause tracheal obstruction, bone pain, or threaten neurological injury--for example, vertebral metastasis.

John W Williams consultant radiologist, Department of Radiology, Conwy and Denbigshire NHS Trust

Maktoum Azeez senior house officer, Department of General Medicine, Conwy and Denbigshire NHS Trust
Email: makdoc@yahoo.com



References

1. Koike E, Yamashita H, Watanabe S, Ymashita H, Nogochi S. Brachiocephalic vein thrombus of papillary thyroid cancer. Surg Today 2002;32:59-62.
2. Dutta D, Lahiri B. Recurrent thyroid carcinoma presenting as an endotracheal nodule. Connecticut Med 2002 Oct;66.
3. Frazell EL, Foote FW Jr. Papillary cancer of the thyroid; a review of 25 years of experience. Cancer 1958;11:895-922.
4. Onaran Y, Terzioglu T, Oguz H, Kapran Y, Tezelman S. Great cervical vein invasion of thyroid carcinoma. Thyroid 1998;8:59-61.
5. Patel PC, Millman B, Pellitteri PK, Woods EL. Papillary thyroid carcinoma presenting with massive angioinvasion of the great vessels of the neck and chest. Otolaryngol Head Neck Surg 1997;117(suppl):S117-20.

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