Supplementary Material for: Polypoid malignant melanoma with spontaneous decapitation showing favorable prognosis: a case report

Introduction: Regression of malignant melanoma (MM) is commonly observed phenomenon, which refers to disappearance or loss of all or part of MM. It can be identified both clinically and histologically, and high probability of histological regression of MM (10%-58%) has been reported. However, the decapitation of skin tumor has rarely been described in the English literature, and decapitation in MM has not been reported. Here, we report the case of polypoid MM with spontaneous decapitation.
Case presentation: An 81-year-old Japanese woman was referred to our hospital due to a polypoid nodule on her cheek. She was diagnosed with MM at stage IIC (T4bN0M0) by histological examinations. Three weeks after the biopsy, the nodule decapitated spontaneously without bleeding, and an ulcer developed on the base of the polypoid nodule. The histological examination of the additionally resected ulcerative lesion under the nodule revealed infiltration of T cells mainly composed of CD8⁺ natural killer T cells. No recurrence nor metastasis has been observed for 4 years.
Conclusion: This is the first case report of polypoid MM with spontaneous decapitation, which may be attributed natural killer T cells. Moreover, this case shows favorable prognosis, while it is said that the regression in thick MM doesn’t have prognostic advantage and polypoid topography has been reported to be related to extremely poor prognosis. Further investigations are needed to evaluate the prognostic advantage of decapitation in MM and other skin tumors.

引言：恶性黑色素瘤（malignant melanoma, MM）消退是一种常见临床现象，指恶性黑色素瘤全部或部分消失。该现象可通过临床及组织学检查检出，已有文献报道恶性黑色素瘤的组织学消退率可达10%~58%。然而，皮肤肿瘤断离现象在英文文献中鲜有报道，而恶性黑色素瘤的断离病例至今未见报道。本文报告1例伴自发性断离的息肉样恶性黑色素瘤病例。

病例报告：患者为81岁日本女性，因面颊部出现息肉样结节就诊于我院。经组织学检查，患者被确诊为IIC期恶性黑色素瘤（T4bN0M0）。活检术后3周，该结节自发性断离且无出血，息肉样结节基底部形成溃疡。对结节下方额外切除的溃疡性病灶行组织学检查，结果显示以CD8+自然杀伤T细胞为主的T细胞浸润。随访4年，未观察到肿瘤复发及转移。

结论：本研究首次报道伴自发性断离的息肉样恶性黑色素瘤病例，该现象可能与自然杀伤T细胞相关。此外，该病例呈现良好预后；而既往研究认为，厚型恶性黑色素瘤的消退并无预后优势，且息肉样形态学特征与极差的预后相关。未来需开展进一步研究，以评估恶性黑色素瘤及其他皮肤肿瘤断离现象的预后价值。