Basal Cell Carcinoma of Infra-Auricular Skin Extending to Parotid Gland and Follicular Carcinoma of Thyroid Presenting as Synchronous Double Primary: A Case Report and Literature Review

Basal cell carcinoma (BCC) is the most common skin cancer, accounting for over two‑thirds of cases worldwide. The incidence is higher in developed countries, and most cases are sporadic. Lesions of the head and neck are considered high‑risk when more than 2 centimeters in size, have irregular borders, or are infiltrative. However, those occurring in the mask area of the face, including the peri‑auricular region, are classified as high‑risk regardless of size. We report a middle‑aged woman with a 3‑year history of a non‑healing infra‑auricular ulcer on right side of face extending to the right ear lobule. MRI demonstrated tumour extension into the superficial lobe of the right parotid gland, and the neck ultrasonography revealed bilateral thyroid nodules with hypoechoic nodules and hyperechoic foci. Biopsy from the lesion was reported as BCC, and the Fine‑needle aspiration from thyroid nodule suggested follicular neoplasm. Following a multidisciplinary tumour board review, the patient underwent wide local excision with superficial parotidectomy and total thyroidectomy in a single operative session, with local skin flap reconstruction. Histopathology confirmed infiltrative BCC with parotid invasion and minimally invasive follicular thyroid carcinoma. Post‑operatively, the patient received radioiodine ablation and thyroxine suppression. At one‑year follow‑up, she is disease‑free. Direct parotid invasion by BCC is uncommon, and synchronous presentation with follicular thyroid carcinoma is extremely rare. Careful clinic-radiological evaluation and planning led to a single‑stage surgical management, which facilitated complete tumour clearance, functional preservation, and cosmetically acceptable reconstruction in this patient. This case emphasises the need for thorough assessment for second primary malignancies in patients with high‑risk skin cancers.