Squamous Cell Carcinoma of the Scalp Masquerading as Trichilemmal Tumor of the Scalp

Background: Adnexal components tumors of the skin are very rare and are seen as benign lesions of the scalp in aged women. Trichilemmal tumor is usually benign and rarely under­ goes malignant transformation in a stepwise manner starting with an adenomatous stage of the trichilemmal cyst to an epitheliomatous stage of the proliferating trichilemmal tumor (PTT) evolving into the carcinomatous stage of the malignant proliferating trichilemmal tumor (MPTT). Case report: A 53­year­old woman reported with huge swelling in the posterior region of the scalp. The swelling was mobile and soft to firm in consistency not fixed to the skull bone. The surface was smooth and getting under the swelling was not possible, needle biopsy reported as trichilemmal tumor. Contrast enhanced computed tomography (CECT) neck did not show any nodes in the neck, especially the posterior compartment. The tumor was widely excised with 1 cm margin and the periosteum was kept intact with split skin graft. An area of periosteal adher­ ence to the tumor seen was excised. The histopathology report on serial sectioning reported grade 1 moderately differentiated squamous cell carcinoma (SCC). Postoperative external beam radiotherapy of 66 Gy was given. The patient is being followed up and no recurrence is seen. Conclusion: Malignant transformation in a proliferating trichilemmal tumor a rare entity and should be differentiated from SCC and the better prognostic trichilemmal carcinoma. A protocol­based adjuvant therapy is available for squamous cell carcinoma but not for trichilemmal carcinoma (TLC) and MPTT. A major meta­analysis may help to establish a clinical outcome­ based classification and management protocol for these tumors.