Diagnostic utility of adipophilin immunostain in periocular carcinomas

Abstract

Purpose: To determine the efficacy of adipophilin immunohistochemistry in the diagnosis of sebaceous carcinoma of the ocular adnexal region and to provide the guidelines for interpretation of this immunostain.

Design: Retrospective, histopathologic case series.

Participants: A total of 25 patients with sebaceous carcinoma, 21 patients with basal cell carcinoma, 22 patients with conjunctival squamous cell carcinoma, 9 patients with cutaneous squamous cell carcinoma, and 5 patients with conjunctival mucoepidermoid carcinoma.

Methods: Immunohistochemical staining for adipophilin was performed on paraffin-embedded tissues and correlated with hematoxylin-eosin, periodic acid-Schiff (PAS), and mucicarmine-stained preparations. Immunostaining was quantified by light microscopy and with a computerized image analysis system of scanned images. Statistical analysis was performed to compare immunostaining patterns within the tumor categories by stage and grade, between the different neoplasms, and for correlation between light microscopy observations and computerized image analysis.

Main outcome measures: Localization of adipophilin immunostain, intensity of immunostaining, percent of immunoreactive cells, percentages of vacuolar staining and granular staining, and vacuole size.

Results: Adipophilin expression was observed in 100% of sebaceous carcinomas, 100% of cutaneous squamous cell carcinomas, 95% of basal cell carcinomas, 73% of conjunctival squamous cell carcinomas, and 60% of mucoepidermoid carcinomas. Sebaceous carcinomas demonstrated significantly stronger adipophilin expression, a greater number of intracytoplasmic vacuoles, and larger vacuoles. The specificity and sensitivity of adipophilin immunostaining in the diagnosis of sebaceous carcinoma were both 100% when more than 5% of the staining occurred in vacuoles (<95% granular staining). The diagnostic sensitivity and specificity were 100% and 96%, respectively, when the staining was graded as moderately or strongly intense and were 92% and 85% when the vacuoles were greater than 1.5 μm in diameter.

Conclusions: Although upregulation of neoplastic steatogenesis is observed in both sebaceous and nonsebaceous carcinomas, the pattern and intensity of adipophilin immunostaining are helpful in distinguishing sebaceous carcinoma from other neoplasms with overlapping histology.