↓↓English Below↓↓
皆さんこんにちは！！東京都千代田区 麹町駅と半蔵門駅の間 新宿通り沿いのビル２階・３階にある整形外科クリニック“One Clinic 麹町（ワンクリニック麹町）”院長の栗本です。
まだまだ暑さが続きますが皆様いかがお過ごしでしょうか？
今回は繰り返す膝等の腫れのなかで少しニッチな疾患「TGCT」について書いてみたいと思います。
腱滑膜巨細胞腫（TGCT）は、関節や腱鞘、滑液包の内側を覆う「滑膜」に発生するまれな腫瘍です。多くは良性で、転移することはほとんどありません。
しかし、病変が大きくなったり関節内に広がったりすると、痛みや腫れ、動かしにくさを引き起こし、骨や軟骨に影響することがあります。
「良性だから心配ない」とは一概にいえず、病型や発生部位に応じた診断と治療が大切です。
1．TGCTの2つの病型
- 限局型TGCT：境界のはっきりした単発のしこりとして現れることが多く、手指や足趾などの小さな関節、腱鞘に好発します。比較的ゆっくり成長し、切除しやすいケースが多い病型です。
- びまん型TGCT：滑膜に沿って広い範囲に増殖し、膝、股関節、足関節などの大きな関節に多くみられます。周囲の組織へ入り込みやすく、限局型よりも再発や関節障害が問題になりやすい病型です。
2．TGCTはなぜ起こるのか
TGCTでは、一部の腫瘍細胞に遺伝子の変化が起こり、CSF1というタンパク質が過剰につくられることが発症に関係すると考えられています。
CSF1はマクロファージなどの細胞を呼び寄せる働きがあり、集まった細胞が病変の大部分を形成します。かつては炎症性疾患に近いものと考えられていましたが、現在は腫瘍性病変として理解されています。
ただし、一般に親から子へ受け継がれる遺伝性疾患ではありません。また、けがや運動、食生活など特定の生活習慣だけが原因になるわけでもなく、確実な予防法は現在のところありません。
3．主な症状
症状は病型や発生部位によって異なります。限局型では、手指などに痛みの少ないしこりとして気づくことが多く、腫瘍が大きくなると腱の動きを妨げ、指を曲げ伸ばししにくくなることがあります。
びまん型では、関節の出血に伴う腫れ（関節穿刺で血液混じりの関節液が引けます）、鈍い痛み、こわばり、可動域の低下などが徐々に現れます。
関節内で出血を繰り返すと、水や血液がたまり、腫れが引きにくくなることもあります。
TGCTの症状は、変形性関節症、半月板損傷、ガングリオン、腱鞘炎などにも似ています。そのため、最初は別の病気と考えられ、診断まで時間がかかるケースもあります。
原因のはっきりしない腫れや痛みが長く続く場合は、画像検査を含めた詳しい評価が必要です。
4．検査と診断
診断で特に重要なのがMRIです。TGCTでは、病変内の出血に由来するヘモジデリンが沈着し、MRIで黒く見える特徴的な低信号や「ブルーミング」と呼ばれる所見がみられます。
MRIは、病変の大きさだけでなく、関節内外への広がりや骨・軟骨への影響を確認し、治療方針を考えるうえでも役立ちます。
X線やCTでは骨びらん、関節変形などを評価します。最終的には、手術や生検で採取した組織を顕微鏡で調べ、確定診断を行います。
5．治療はどのように決める？
治療は、発生部位、症状、病変の広がり、再発の有無などを総合して決めます。症状が軽く、進行がゆるやかな場合には、MRIなどで変化を確認しながら経過観察を選ぶこともあります。
一方、痛みや機能障害があり、切除による改善が期待できる場合は手術が基本です。
限局型では、周囲の腱や神経を傷つけないように腫瘤を丁寧に切除します。びまん型では、病変の位置に応じて関節鏡手術、切開して行う手術、または両者を組み合わせた滑膜切除が選ばれます。
大切なのは、単に病変をすべて取り切ることだけを目指すのではなく、再発を抑えながら関節機能をできる限り守ることです。
無理な切除がかえって機能障害につながる場合もあるため、治療経験のある専門医による判断が欠かせません。
手術が難しい、再発を繰り返す、手術によって大きな機能低下が予想される症候性TGCTでは、CSF1受容体を標的とする薬物療法が海外で実用化されています。
日本では薬剤ごとに承認状況が異なるため、治療を検討する際は、治験を含む最新情報を専門施設で確認する必要があります。
6．治療後のリハビリと経過観察
手術後は、腫れや痛みを抑えながら関節の動きを保ち、筋力や日常動作を段階的に戻していきます。リハビリの開始時期や荷重の程度は、手術部位、切除範囲、軟骨の状態などによって異なります。
自己判断で急に運動量を増やさず、医師や理学療法士の指示に沿って進めることが大切です。
特にびまん型では、治療後も局所再発が起こる可能性があります。症状が落ち着いていても、診察やMRIによる定期的な経過観察が重要です。
再び腫れが続く、痛みが強くなる、関節が動かしにくくなるといった変化があれば、早めに受診しましょう。
7．気になる症状があればご相談ください
TGCTは良性腫瘍ですが、病変の広がりによっては、関節の痛みや腫れを繰り返し、日常生活や仕事、スポーツに影響することがあります。
手指のしこりが少しずつ大きくなる、関節の腫れがなかなか引かない、何度も水がたまる、原因不明の可動域制限が続く場合は、一度整形外科を受診してください。
びまん型が疑われる場合や、再発例、手術の判断が難しい場合には、関節外科や骨・軟部腫瘍を専門とする医療機関への相談も重要な選択肢です。
早い段階で病変の範囲を把握し、自分の症状や生活に合った治療方針を一緒に考えることが、関節機能を守る第一歩です。
いつでもお気軽にご相談ください。
こちらからも診療予約が可能です!(^^)!
Hello everyone! This is Dr. Kurimoto, Director of “One Clinic Kojimachi,” an orthopedic clinic located on the 2nd and 3rd floors of a building along Shinjuku-dori, right between Kojimachi Station and Hanzomon Station in Chiyoda-ku, Tokyo.
As the hot weather persists, how is everyone holding up? This time, I would like to write about “TGCT,” a somewhat niche condition that can be behind recurrent swelling in joints like the knee.
Tenosynovial Giant Cell Tumor (TGCT) is a rare tumor that develops in the “synovium,” which lines the inside of joints, tendon sheaths, and bursae. Most cases are benign and rarely metastasize. However, as the lesion grows or spreads within a joint, it can cause pain, swelling, and movement restriction, as well as affect surrounding bones and cartilage. Therefore, we cannot simply say, “It’s benign, so there’s nothing to worry about.” Accurate diagnosis and treatment tailored to the specific type and location of the tumor are crucial. In this article, I will introduce the characteristics, symptoms, diagnosis, treatment, and guidelines on when to see a doctor for TGCT in as clear a manner as possible.
- The Two Types of TGCT
- Localized TGCT: Typically appears as a single, well-defined lump. It most commonly occurs in small joints and tendon sheaths, such as those in the fingers and toes. It tends to grow relatively slowly and is generally easier to excise surgically.
- Diffuse TGCT: Proliferates extensively along the synovium and is often seen in large joints like the knee, hip, and ankle. Because it easily infiltrates surrounding tissues, local recurrence and joint impairment are much more problematic compared to the localized form.
- Why Does TGCT Occur? In TGCT, genetic alterations in a subset of tumor cells lead to an overproduction of a protein called CSF1, which is believed to drive the disease. CSF1 acts by recruiting immune cells such as macrophages, and these recruited cells form the majority of the lesion. While TGCT was previously thought to be an inflammatory disease, it is now understood as a neoplastic (tumor-like) process. However, it is generally not an inherited genetic disease passed from parent to child. Nor is it caused solely by specific lifestyle habits like injuries, exercise, or diet, and there are currently no proven ways to prevent it.
- Main Symptoms Symptoms depend on the type and location of the tumor. In localized TGCT, people often notice a painless lump in areas like the fingers. As the tumor grows, it can interfere with tendon movement, making it difficult to bend or extend the finger. In diffuse TGCT, symptoms such as joint swelling, a dull ache, stiffness, and reduced range of motion gradually appear. Repeated bleeding inside the joint can cause fluid or blood to accumulate, making the swelling persistent. The symptoms of TGCT often resemble those of osteoarthritis, meniscal tears, ganglion cysts, or tenosynovitis. As a result, it may initially be misdiagnosed as another condition, taking time to reach an accurate diagnosis. If unexplained swelling or pain persists over a long period, a detailed evaluation—including advanced imaging—is necessary.
- Testing and Diagnosis MRI is particularly critical in diagnosing TGCT. Because TGCT lesions accumulate hemosiderin resulting from internal bleeding, they display characteristic low signal intensity (dark areas) and a finding called the “blooming effect” on MRI scans. In addition to assessing lesion size, MRI helps confirm whether the tumor has spread inside or outside the joint and evaluate its impact on bone and cartilage, making it essential for planning treatment strategies. X-rays and CT scans are used to evaluate bone erosion and joint deformation. Ultimately, a definitive diagnosis is made by examining tissue obtained via surgery or biopsy under a microscope.
- How is Treatment Decided? Treatment is determined comprehensively based on factors such as location, symptoms, the extent of the lesion, and whether it has recurred. If symptoms are mild and progression is slow, watchful waiting with periodic MRI check-ups may be selected. On the other hand, if there is pain or functional impairment that is expected to improve with resection, surgery is the primary option. For localized TGCT, the mass is carefully excised to avoid damaging nearby tendons and nerves. For diffuse TGCT, options include arthroscopic surgery, open surgery, or a combination of both to perform a synovectomy, depending on the location of the lesion. What matters most is not simply trying to remove every trace of the lesion at all costs, but minimizing recurrence while preserving joint function as much as possible. Aggressive resection can sometimes lead to greater functional disability, making the judgment of a specialist experienced in managing TGCT essential. For symptomatic TGCT cases where surgery is difficult, recurrence is frequent, or surgical intervention is expected to cause significant functional decline, drug therapies targeting CSF1 receptors have been brought to practical use overseas. Because approval status varies by medication in Japan, it is important to verify the latest information—including clinical trials—at a specialized medical facility when considering systemic therapy.
- Post-Treatment Rehabilitation and Follow-up Following surgery, the goal is to maintain joint range of motion while managing swelling and pain, gradually restoring muscle strength and daily mobility. The timing of starting rehabilitation and weight-bearing restrictions vary depending on the surgical site, extent of resection, and state of the cartilage. It is crucial not to increase activity levels precipitously on your own, but to progress under the guidance of your doctor and physical therapist. Particularly with diffuse TGCT, local recurrence remains a possibility even after treatment. Even if symptoms have settled down, regular follow-up through clinical examinations and MRI scans is essential. If you notice persistent swelling, worsening pain, or difficulty moving the joint again, be sure to seek medical advice promptly.
- Consult an Orthopedic Specialist If You Have Concerning Symptoms Although TGCT is a benign tumor, depending on its spread, recurring joint pain and swelling can significantly impact daily life, work, and sports. If you notice a lump on your finger that is gradually enlarging, joint swelling that doesn’t go away, recurrent fluid accumulation, or an unexplained loss of motion, please consult an orthopedic surgeon. If diffuse TGCT is suspected, or in cases of recurrence or complex surgical decision-making, seeking a consultation at a specialized medical facility specializing in joint surgery or bone and soft tissue tumors is a great option. Identifying the extent of the lesion at an early stage and working together to establish a treatment strategy that fits your symptoms and lifestyle is the first step toward protecting your joint function.
