Parathyroid

Hyperparathyroidism is due to oversecretion of parathormone and results in hypercalcaemia. It arises in three main contexts.

1. Primary hyperparathyroidism—oversecretion by one or more parathyroid glands sometimes due to diffuse hyperplasia(10-25% of cases, 25% of which are associated with MEN I and II syndromes) but more commonly (70-80% of cases) an adenoma.

2. Secondary hyperparathyroidism—as a physiological response of all four glands to chronic hypocalcaemia due to renal failure, malabsorption or vitamin D deficiency.

3. Tertiary hyperparathyroidism—autonomous hypersecretion in longstanding secondary hyperparathyroidism after correction of the hypercalcaemia.

Investigation is by serum calcium, phosphate and parathormone levels, and isotope scan with CT scan and MRI. Treatment is by removal of the adenoma (usually solitary, occasionally two) or hyperplastic glands, leaving a small amount (100mg) of functioning tissue. Histologically there is overlap in the features of adenoma and nodular hyperplasia and designation is more appropriately decided by the number of enlarged glands (adenoma is usually solitary) and the clinical context. What is of crucial importance is that the pathologist confirms by frozen section to the surgeon that parathyroid tissue has been excised at neck exploration and not lymph node, thymic remnant or thyroid nodule. To this end each submitted specimen is finely weighed and its nature confirmed indicating whether there is any need for further surgical exploration.

Parathyroid carcinoma is rare (<2% of cases) and in elderly patients with high levels of parathormone. It may infiltrate adjacent soft tissues with difficulty in surgical excision. Histologically it has a solid or tra-becular pattern with thick fibrous bands traversing it. Cytological atypia and mitoses are present but as these can be seen in an adenoma more reliable indicators are soft tissue, perineural and lymphovascular invasion. It may be resected in continuity with the ipsilateral lobe of thyroid gland, and neck dissection is considered for palpable metastases. Cervical and mediastinal lymph nodes, lungs, bone and liver are the commonest sites for metastatic spread.

Respiratory and Mediastinal Cancer

• Lung Carcinoma

• Malignant Mesothelioma

• Mediastinal Cancer

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