Abstract: History and Examination: A 70-year man presented to the General Surgery OPD with the complaint of painless swelling on the right thigh since 2 months. On examination a solitary, round, 10 x 10 cm swelling was noted on the right upper thigh which is non-tender, firm in consistency and with restricted mobility.
Management: Ultrasonogram reveled a well-defined heterogeneous lesion of 8.2 × 7.3 cm on the medial aspect of right upper thigh which was suggestive of either infective etiology or a soft tissue neoplasm. Cytological features were suggestive of infected epidermoid cyst. Lesion was excised with clear margins and intact cyst wall.
Histopathology: Sections showed stratified squamous epithelium with full thickness anaplasia, islands of anaplastic tissue dipping down into the cyst cavity forming sheets of large pleomorphic cells with hyperchromatic nuclei. Well-formed malignant pearls were seen suggestive of squamous cell carcinoma.
Conclusion: Squamous cell carcinoma arising from the epidermal cyst can mimic that of an infected epidermal cyst. In a case of epidermoid cyst, comprehensive pathological search for malignancy is recommended when there is a rapid growth, rare site of origin, overlying skin changes and recurrent infection which is non responsive to medical therapy.
