Atypical Fat Staining Patterns in Hyperparathyroidism

Abstract

Intracytoplasmic lipid content reflects the metabolic state of parathyroid cells, and staining for this is a useful adjunct in the evaluation of parathyroid glands excised in the treatment of hyperparathyroidism. The procedure, however, is not without limitations, as the unexpected presence of lipid in abnormal, hyperfunctioning glands or its absence in normal glands is occasionally encountered. In this study, the authors review the oil red O staining patterns of 524 parathyroidectomy cases to determine the validity of the stain as well as possible clinical and pathologic correlations. Twenty-seven cases (5.2%) were identified with problematic oil red O staining on which adequate clinical follow-up and pathologic material were available for review. Mean follow-up time was 32 months for this subgroup. The most common problem was the presence of lipid within adenomas (19 cases) or hyperplastic glands (6 cases). Markedly decreased or absent lipid in normal, adenoma-associated glands was seen in two cases. The intensity and distribution of lipid staining in hyperfunctioning glands varied. In four cases, 2/19 adenomas and 2/5 hyperplasia, diffuse positivity, similar to normal parathyroid, were observed. If weak or only focally strong staining patterns are considered to be consistent with hyperfunctioning glands, only six cases, two adenomas, two hyperplasias, and two normal glands could not be resolved. Oil red O stain is useful in diagnosing abnormally functioning parathyroid glands, and, if attention is paid to the staining pattern, few atypical patterns are encountered. Int J Surg Pathol 3(3):163-168, 1996