Laryngeal cancer

It is a malignant tumor of the larynx, occurring 95 times more frequently than laryngeal sarcoma, and accounts for about 2% of all cancers in the body. It is most common in people in their 50s and 70s, and is about 9 times more common in men than women. The true cause is unknown, but it is overwhelmingly more common in smokers, and overuse of the voice, exposure to X-rays, and inhalation of irritating gases are well known to be triggers. Laryngeal cancer is classified into vocal cord cancer, supraglottic cancer (false vocal cord cancer, laryngeal ventricle cancer, vestibular cancer, and laryngeal inlet cancer), which is located above the glottis surrounded by the vocal cords on both sides, and subglottic cancer, which is located below the glottis. Of these, vocal cord cancer is the most common, followed by supraglottic cancer and subglottic cancer. However, as vocal cord cancer progresses, it can also progress to the upper and lower parts of the glottis and outside the laryngeal inlet. Vocal cord cancer is often discovered early because it causes hoarseness from the very early stages, and because metastasis to the cervical lymph nodes and other areas is less common than cancers in other parts of the body, the prognosis is very good and the cure rate is over 90%. Conversely, laryngeal cancer, which is not a vocal cord cancer, has very few subjective symptoms, so it is often not discovered until it has progressed significantly, and its prognosis is worse than that of vocal cord cancer, but laryngeal cancer is easier to treat than cancers in other parts of the body and often has a good prognosis.

Early symptoms of vocal cord cancer include hoarseness, and of other cancers, a foreign body sensation. If these symptoms persist for more than two weeks, it is advisable to be examined by an otolaryngologist. As laryngeal cancer progresses, symptoms such as bloody sputum, pain, wheezing, breathing problems, and swallowing problems may occur, but these symptoms do not appear until the cancer has progressed significantly. Metastasis occurs most frequently in the cervical lymph nodes, followed by the trachea and lungs. In the terminal stages, metastasis occurs throughout the body, including the liver.

Regarding treatment, radiation therapy is an excellent treatment for early-stage cancer because it does not impair vocal function, and can even lead to a complete cure. For more advanced cancers, surgical treatment is indicated. Depending on the location of the cancer, it may be possible to preserve the voice to some extent by partially removing the larynx. If the entire larynx is removed, the patient is no longer able to speak using the vocal cords and must use esophageal voice or an artificial larynx to produce sound, but with training it is possible to recover to a level where it has little effect on social life. Anticancer drugs have made considerable progress in recent years, but for laryngeal cancer they are still only a supportive treatment.

[Masami Kawamura]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

喉頭の悪性腫瘍(しゅよう)で、喉頭肉腫の95倍も発生頻度が高く、全身の癌の約2％を占める。50～70歳代にもっとも多く、性別では男性に多くみられ、女性の約9倍である。真の原因は不明であるが、喫煙者に圧倒的に多く、声の酷使やX線などの照射、刺激性ガス吸入などが誘因としてよく知られている。喉頭癌は、声帯癌、声帯で左右を囲まれた声門より上部にある声門上癌（仮声帯癌、喉頭室癌、前庭部癌、喉頭入口部癌）、声門より下部にある声門下癌に分類されている。これらのうち声帯癌がもっとも多く、ついで声門上癌、声門下癌となる。しかし声帯癌も進行すると、声門上部や下部、さらに喉頭入口部の外側へも進展する。声帯癌はきわめて初期から声がかれてくるので早期に発見されることが多く、しかも頸部(けいぶ)リンパ節をはじめとした転移も他の部位の癌よりも少ないので、予後はきわめてよく治癒率も90％以上である。声帯癌以外の喉頭癌は逆に自覚症状がきわめて少ないので、相当進行してからでないと発見されないことが多く、予後も声帯癌よりは悪いが、身体他部の癌と比べると喉頭癌は治療しやすく、予後もよいことが多い。

　初期の症状としては、声帯癌では嗄声(させい)（しわがれ声）であり、その他の癌では異物感である。2週間以上もこのような症状があるときには、耳鼻咽喉(いんこう)科医による検査を受けるのがよい。喉頭癌が進展してくると、血痰(けったん)、疼痛(とうつう)、喘鳴(ぜんめい)や呼吸障害、嚥下(えんげ)障害などをおこすが、相当進行してからでないとみられない症状である。転移は頸部リンパ節がもっとも多く、ついで気管と肺に多い。末期になると、肝臓をはじめ全身に転移をおこしてくる。

　治療は、早期のものは放射線療法が声の機能を障害せずに治療できる点で優れており、しかも完治させることができる。進展したものでは手術的治療が適応となる。癌の進展する部位によっては、喉頭を部分的に切除することによって声をある程度まで保存できることもある。喉頭を全部摘出した場合は、声帯による発声ができず食道音声や人工喉頭による発声を行わなければならないが、訓練をすれば社会生活にほとんど支障ない程度にまで回復させることができるようになる。抗癌剤も最近は相当進歩してきているが、喉頭癌についてはまだ補助的治療の域を出ないのが現状である。

［河村正三］

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