Background Cutaneous malignancies are rare complications of Lynch syndrome and can include Muir-Torre and Turcot syndromes that are associated with sebaceous gland tumors and keratoacanthomas. The incidence and clinical course of cutaneous squamous cell carcinoma have not been well documented in Lynch syndrome due to its rarity. Case presentation A 49-year male presented with an enlarging groin skin lesion that was biopsed and demonstrated cutaneous squamous cell carcinoma for which he underwent a surgical resection. The patient experienced later a recurrence of cutaneous squamous cell carcinoma around the resected margins. Next generation sequencing of tumor tissue revealed mutations in MSH6 and MLH1, in addition to high microsatellite instability. The patient underwent pembrolizumab treatment with complete resolution of the cutaneous lesion in the groin, but subsequently developed a new mass in the right antecubital fossa shortly after discontinuation of pembrolizumab. Repeat biopsy of the antecubital fossa lesion revealed a recurrence of cutaneous squamous cell carcinoma. Germline mutation testing revealed MLH1 mutation, compatible with Lynch syndrome, and the patient restarted pembrolizumab which was associated with a complete response. The patient was referred for genetic counseling and cancer screening. Conclusions Cutaneous squamous cell carcinoma, although rare, can be the initial presenting symptom in patients with Lynch syndrome. This association has been described in patients with germline mutations in MLH1. Lynch syndrome should be considered when evaluating young patients presenting with recurrent cutaneous squamous cell carcinoma with positive family history of malignancy and/ or without any identifiable risk factors for skin cancers, including those with a durable and rapid response to immunotherapy.

中文翻译：

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年轻患者的异时性皮肤鳞状细胞癌是发现具有 MLH1 Germline 突变的 Lynch 综合征的唯一症状

背景皮肤恶性肿瘤是 Lynch 综合征的罕见并发症，可包括与皮脂腺肿瘤和角化棘皮瘤相关的 Muir-Torre 和 Turcot 综合征。由于其罕见，Lynch 综合征中皮肤鳞状细胞癌的发病率和临床病程尚未得到很好的记录。病例介绍 一名 49 岁男性出现扩大的腹股沟皮肤病变，活检显示为皮肤鳞状细胞癌，为此他接受了手术切除。患者后来经历了切除边缘周围皮肤鳞状细胞癌的复发。肿瘤组织的下一代测序揭示了 MSH6 和 MLH1 的突变，以及高度的微卫星不稳定性。患者接受了 pembrolizumab 治疗，腹股沟的皮肤病变完全消退，但随后在停用 pembrolizumab 后不久，右侧肘窝出现了新的肿块。肘前窝病变的重复活检显示皮肤鳞状细胞癌复发。种系突变检测显示 MLH1 突变，与 Lynch 综合征相容，患者重新开始使用 pembrolizumab，这与完全缓解相关。该患者被转介进行遗传咨询和癌症筛查。结论 皮肤鳞状细胞癌虽然罕见，但可能是 Lynch 综合征患者的首发症状。这种关联已在 MLH1 种系突变的患者中得到描述。