Merkel Cell Carcinoma With True Direct Parotid Gland Invasion

초록

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin malignancy. We report an exceptional case of a 71-year-old female presenting with a 5.7-cm MCC in the left parotid region, representing a rare case of true direct parotid parenchymal invasion—distinguished from the more common intraparotid nodal metastasis—alongside multiple regional nodal metastases. The patient underwent wide en bloc excision, superficial parotidectomy, and selective neck dissection. Despite tumor adherence, the main facial-nerve trunk was successfully preserved. The resulting 12×11 cm composite defect was reconstructed using an anterolateral-thigh (ALT) free flap. Pathology confirmed cutaneous MCC with direct parotid parenchymal invasion, lymphovascular/perineural invasion, and metastatic nodes (Stage IIIB). Postoperatively, the flap remained viable, with successful functional preservation of facial-nerve function. Due to high-risk features, adjuvant chemoradiotherapy was initiated. This case highlights the importance of distinguishing invasion pathways for accurate staging and demonstrates that aggressive resection with functional reconstruction is feasible and effective for managing advanced craniofacial MCC. It also emphasizes the clinical importance of differentiating true parotid invasion from intraparotid nodal metastasis. Merkel cell carcinoma (MCC) is a rare but highly aggressive neuroendocrine skin malignancy that typically arises on sun-exposed areas in elderly or immunocompromised individuals.1 It usually presents as a rapidly enlarging, painless, violaceous nodule, and early regional or distant metastasis occurs in up to 30% of cases.2,3 Despite its low incidence (≈ 0.7 per 100,000), MCC exhibits one of the highest mortality rates among cutaneous malignancies, largely due to early lymphovascular dissemination.1 In the head-and-neck region, parotid involvement by MCC typically occurs through lymphatic metastasis to the intraparotid lymph nodes. However, true direct parenchymal invasion from an overlying cutaneous primary breaching the parotid capsule is exceedingly rare and presents distinct diagnostic and staging challenges.4 Herein, we present an exceptional case of MCC demonstrating true direct parenchymal invasion into the parotid gland, successfully managed with multidisciplinary treatment.

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