Desmoplastic tricholemmoma of the eyelid misdiagnosed as sebaceous carcinoma: a potential diagnostic pitfall

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Abstract
Sebaceous carcinoma (SC) most commonly presents on the eyelid and is frequently misdiagnosed both clinically and pathologically. Only very rare cases of desmoplastic tricholemmoma (DTL) of the eyelid have been reported. We present a case of DTL of the eyelid initially misdiagnosed as an invasive SC. A 55-year-old man presented with a rapidly growing 5 mm erythematous lesion on his upper eyelid. Histologic examination showed a lobular, folliculocentric proliferation of palely eosinophilic to clear cells surrounded by peripheral basal cells with palisading. The central portion of the lesion appeared infiltrative with clear cells surrounded by a thickened basement embedded in a dense, collagenous stroma. However, the cells showed mostly uniform cytoplasmic clearing, lacking the multivacuolization or nuclear scalloping of sebocytes. In addition, a periodic acid Schiff stain was positive with diastase sensitivity, indicating cytoplasmic glycogen, not lipid. CD34 immunohistochemical staining was also positive, which has been reported in DTL but not in SC. SC is often misdiagnosed as other entities, but misidentification of other neoplasms as SC is less common; however, this is an important diagnostic pitfall, as it may result in unnecessary and disfiguring surgical treatment and consequent medical-legal liability. Therefore, DTL should enter the differential diagnosis of clear-cell neoplasms on the eyelid.