29. Parathyroid adenoma

Overview

Staining: HE

Organ: Parathyroid

Description:

The tumor is encapsulated. It is comprised of two types of cells:

• Chief cells – pale cytoplasm
• Oxyphilic cells – eosinophilic cytoplasm

The tumor cells show no atypia as this is a benign tumor. The tumor forms no structures. It also contains no adipose tissue, unlike the normal parathyroid gland.

Diagnosis: Parathyroid adenoma

Causes:

• Sporadic
• Multiple endocrine neoplasia (MEN)

Theory:

Oxyphilic and chief cells

Parathyroid adenoma must be differentiated from parathyroid hyperplasia and parathyroid carcinoma during histological examination. Parathyroid adenoma has a rim of normal parenchyme surrounding it. If this was PTH hyperplasia no normal parenchyme would be seen. Also, in PTH adenoma is only one PTH gland enlarged while in hyperplasia all glands are enlarged.

To differentiate parathyroid adenoma and carcinoma, one must inspect the number of fat cells (among other factors, like invasion of structures or metastasis). Characteristic for parathyroid carcinoma is the decreased number of adipocytes.