Localized myxedema is a rare complication ofautoimmune thyroid diseases including the Hashimoto thyroiditis and Graves’ disease.Localized myxedema results from the accumulation of glycosaminoglycans in the dermis and subcutaneous layer of the skin.

Fibroblast-produced hyaluronic acid is the mainglycosaminoglycan in localized myxedema. Localized myxedema presents bilaterally with a “boggy” thickening of the skin. Lesions classically have “waxy” swelling and induration.Myxedematous lesions of the skin most often appear on the anterior aspects of the legs and dorsum of the feet. They are often asymptomatic. Targeted treatment to cutaneous lesions is usually reserved for symptomatic cases.

The histopathology of sebaceous carcinoma (SBC) can mimic other skin neoplasms, including basal cell carcinoma (BCC).Therefore, diagnostic biomarkers are needed for a subset of cases. Normal sebaceous glands express PRAME (PRAME nuclearreceptor transcriptional regulator), a melanoma-associated biomarker.Donell et al. showed that PRAME has strong immunoreactivity with basaloid sebocytes in SBC. Ng et al. reported patchy cytoplasmic staining in the germinative sebocytes only.Sebaceous glands (H&E stain and PRAME stain)

Objective: to evaluate the utility of PRAME immunohistochemistry as a diagnostic biomarker for SBC and its usefulness in the distinction of SBC from BCC.