Case: A 91-year-old female patient applied to our dermatology clinic with rash on the right cheek. She has noticed it for the last one year. Excisional biopsy was performed after punch biopsy. Clinical diagnoses were actinic keratosis and squamous cell carcinoma. On histopathological examination, atypical epithelial cell proliferation resembling basaloid germinative cells which displayed connection to the overlying epidermis was observed. These cells formed intraepidermal lobular arrangements which invaginated into the superficial dermis. Fine vacuoles suggesting sebaceous differentiation in some cell cytoplasm and scalloped nuclei were noted. Numerous mitoses were observed. No invasive tumor area was present. In the immunohistochemical study, diffuse and strong positive staining was detected with EMA and androgen receptor.

Conclusion: SCis can be interpreted clinically and microscopically as actinic keratosis or squamous cell carcinoma in situ (SCCis). It may be accompanied by Muir Torre Syndrome and therefore, being aware of the existence of this entity is important to avoid misdiagnosis. Anahtar Kelimeler : Sebaceous carcinoma, Sebaceous carcinoma in situ, Sebaceous differentiation, Muir Torre Syndrome