Parathyroid lipoadenomas and lipohyperplasias: clinicopathologic correlations.

Parathyroid lipoadenomas and lipohyperplasias are rare histologic variants with both an increase in stromal fat and parenchyma. We report the most comprehensive single institution series of lipoadenomas and lipohyperplasias to date and review the literature. Eight lipoadenomas and 3 lipohyperplasias (27 y period) were reviewed. The mean age was 60.3 years (range: 50 to 77 y) with a female predilection (1.75:1). The most common symptoms on presentation were fatigue (55.6%) and bone/joint pain (44.4%). Only 1 patient was euparathyroid. Ultrasound localized lipoadenomas in 50% of tested cases whereas sestamibi was successful in 71.4%. Despite increased stromal fat (median: 50%), the weight and the appearance of large, occasionally nodular expansions of parathyroid parenchyma within the fatty stroma distinguished lipoadenomas and lipohyperplasias from normal parathyroid tissue; none of the cases were misclassified as normal on frozen section. Mean weight for lipoadenomas was 1553 mg (range: 173 to 4587 mg), whereas the mean weight for lipohyperplasia glands was 389.1 mg. Variant morphologies included follicular patterned, oxyphil predominant, and thymic elements (thymolipoadenoma). In 1 lipohyperplasia case, not all glands were involved. Oil Red O stains showed decreased intracytoplasmic lipid in most cases. Median follow-up was 9.2 months (range: <1 to 51 mo). Only 1 lipohyperplasia patient had persistent hypercalcemia, but was asymptomatic. Lipoadenomas and lipohyperplasias are clinically similar and as histologically diverse as their conventional counterparts. Lipoadenomas are more difficult to localize preoperatively by imaging. Despite the potential difficulty at frozen section, accurate weight documentation and recognition of key histologic features diminish this challenge.