有棘細胞癌の切除縁と治療

Treatment for Cutaneous Squamous Cell Carcinoma

はじめに

　皮膚有棘細胞癌（以下，有棘細胞癌）は，表皮角化細胞（有棘細胞）に由来する悪性腫瘍である。英語表記はほかの粘膜上皮由来の扁平上皮癌（squamous cell carcinoma：以下，SCC）と同様に呼称され，cutaneous SCCやSCC of the skinなどと表現される。本邦において皮膚に関しては有棘細胞癌と表記されるのが一般的であるが，両者は同義である。有棘細胞癌は基底細胞癌の次に多い皮膚悪性腫瘍であり，高齢化に伴い増加傾向にある 1）。本邦においてはボーエン病，日光角化症を含めたSCC in situを含めると最多となるが，除くと同様に基底細胞癌に次ぐ頻度となる 2）。本稿では有棘細胞癌の治療について概説する。

　Cutaneous squamous cell carcinoma (cSCC) is a malignant tumor derived from epidermal keratinocytes (spinous cells). The third edition of the 2020 Japanese Dermatological Association Guidelines for Cutaneous Squamous Cell Carcinoma 2020 states that resection margins should be ≥4–6 mm for low-risk patients and ≥6–10 mm for high-risk patients. Perineural invasion (PNI) is classified as very-high or high-risk for recurrence in the U.S. National Comprehensive Cancer Network (NCCN) guidelines. The possibility of intracranial invasion, especially in the face, should be considered in the treatment of these lesions. Surgeons should perform a detailed histopathologic review to determine the presence/absence of PNI at the margins.

　Prophylactic lymph node dissection is generally not recommended and should be preceded by a lymph node biopsy if lymph node metastasis is suspected on palpation or imaging studies. In the head and neck region, the level of lymph node dissection should be determined by considering the lymphatic flow of the primary tumor, since this region has unique lymphatic flow patterns depending on the primary site.

　Radical radiotherapy is considered for patients who do not consent to surgery or for patients with cSCC who are unable to undergo surgery due to complications.

　In Japan, irinotecan, bleomycin, and peplomycin are covered by insurance as anticancer agents. In February 2024, nivolumab, an immune checkpoint inhibitor, became covered by Japanʼs national healthcare insurance for advanced or recurrent epithelial cutaneous malignancies that cannot be curatively resected. The continued accumulation of cases can be expected to help clarify the optimal treatments for patients with cSCC.