Major Clues and Pitfalls in the Differential Diagnosis of Parathyroid and Thyroid Lesions Using Fine Needle Aspiration Cytology

Abstract

Background: It is difficult to distinguish parathyroid lesions (PLs) from thyroid lesions using fine needle aspiration cytology (FNAC) because of their proximity and their similar cytomorphological features. Methods: FNAC smears of 46 patients with pathologically proven PLs that were histologically diagnosed as parathyroid adenoma (PA, n = 35), parathyroid hyperplasia (PH, n = 3), atypical parathyroid adenoma (APA, n = 1), and parathyroid carcinoma (PC, n = 7) were retrospectively reviewed and analyzed. Results: Our initial cytological diagnoses indicated correct diagnoses in 31 of 46 PL patients (67%). The 15 erroneous diagnoses were 5 patients with non-specific benign disease (11%), 4 with nodular hyperplasia of the thyroid (9%), 5 with atypical cells (11%), and 1 with a metastatic papillary thyroid carcinoma (2%). Follicular pattern, papillary structures, colloid-like material, and macrophages, which often suggest thyroid lesions, were also present in some PLs. We found that branching capillaries along the papillary structures, stippled nuclear chromatin, and frequent occurrence of naked nuclei were useful for determining a parathyroid origin. Conclusions: It is important to be aware that PLs are frequently mistaken for thyroid lesions based on FNAC. The specific and unique characteristics of PLs identified here may be helpful in diagnosis.

Cyto‐morphological features of parathyroid lesions: Fine‐needle aspiration cytology series from an endocrine tumor referral center

“…At our department, we use ICC using antibodies against TTF1 and PTH, but previous work indicate that also GATA3 may facilitate the discrimination between these two tissue types 15 . Moreover, in terms of diagnostic pitfalls when dealing with FNAC on parathyroid lesions, previous studies highlight the risk of falsely diagnosing a papillary thyroid carcinoma 2,3,8 since the presence of tight, three‐dimensional clusters with a central capillary can be seen in smears from a parathyroid lesion—a pattern that may be interpreted as papillary formations. Previous studies have suggested the phenomenon to be correlated to a hypervascular lesion detected on color Doppler sonogram 11 .…”

“…Primary hyperparathyroidism (pHPT) is recognized as symptomatic or asymptomatic hypercalcemia and high to borderline high levels parathyroid hormone (PTH) in the blood. If secondary reasons for hyperparathyroidism have been ruled out (such as renal failure), the cause is one or several parathyroid neoplasms, such as an adenoma (single or multiple) or carcinoma (almost always single nodules) 1,2 . Traditionally, patients were surgically treated using a bilateral neck exploration approach.…”

“…Normal parathyroid glands as well as adenomas usually contain conventional chief cells, with or without smaller populations of clear‐type cell chief cells and oxyphilic cells. Thyroid lesions on the other hand contain follicular epithelial cells—but they are still traditionally difficult to distinguish from parathyroid cells in cytology preparations 2,4,7–13 . The literature regarding cyto‐morphological hallmarks for parathyroid cells is rather limited, and specifically meager in terms of studies that offer clues how to differ parathyroid cells from thyroid epithelium.…”

Immunohistochemical Profile of Parathyroid Tumours: A Comprehensive Review

“…Parathyroid tumours occasionally have to be distinguished from thyroid neoplasms because of close anatomic relation [137] between both glands, including occasional intrathyroidal location of normal parathyroid gland or parathyroid carcinoma. The histogenetic diagnosis is difficult also in fine needle aspiration cytology [138].…”

“…Currently, only few studies have targeted the microenvironment of parathyroid tumours although there are some direct or indirect reports on macrophages [176,177] that were formerly known as a confounding factor in cytology [138,178], and angiogenesis evaluated via morphology or radiological imaging [179,180]. Similarly, scant studies are performed on systemic inflammatory reaction in patients diagnosed with parathyroid tumours [181].…”