The tiny parathyroid adenoma.

In the past 11 years we have operated on three patients with "tiny" parathyroid adenomas (less than 60 mg). Two of these adenomas were virtually indistinguishable visually from the normal glands. (The third adenoma was found only after fixation and permanent sections.) Despite frozen-section diagnoses of "probable hyperplastic tissue" in two cases, these small hyperplastic glands proved confusing at operation. This was especially true of the hyperactive gland embedded within mediastinal tissue that, on initial examination of gross material, had been missed by surgeons and pathologists alike and was discovered only on permanent serial sections. The preoperative laboratory data did not vary substantially from that of other hyperparathyroid patients with larger adenomas; in each case two or more endocrinologists had agreed that parathyroidectomy was indicated and had referred these patients for operation. Permanent microscopic sections confirmed the diagnosis of parathyroid adenoma in all three patients. The clinical and laboratory postoperative data strongly indicate that these small adenomas, masquerading as normal-sized glands, were responsible for the hypercalcemia. These tiny adenomas should be added to the other anatomic and pathologic variations of the parathyroid glands that can prove confusing at operation.