血管内リンパ腫の診断―ランダム皮膚生検の有用性

Diagnosis of Intravascular Lymphoma: Usefulness of Random Skin Biopsies

はじめに

　血管内リンパ腫（intravascular lymphoma：IVL）の生前診断は難しい^1）。日常診療に深く携わる神経内科医であればあるほど，それは十分に理解できるであろう。かつては剖検で診断される例がほとんどであったが，近年では疾患自体の認識が高まったこともあり，生前診断される例が増加してきた。また早期に診断できた場合，新たな分子標的薬リツキシマブ（rituximab）の登場によって，治療成績，予後ともに著しい改善が見込まれるようになった^2）。そのためにも生前診断の重要性がさらに増してきている。

　本稿では，IVLにおける診断の過程についてまとめ，また最近話題となっている，ランダム皮膚生検の有用性についても，筆者らの経験^3）を踏まえながら述べる。

Abstract

　Background: Intravascular lymphomatosis (IVL) is a rare subtype of diffuse large B cell lymphoma, characterized by the presence of tumor cells only in the lumina of small vessels.　Antemortem diagnosis of IVL is extremely difficult because of its varied clinical presentation and absence of lymphadenopathy.

　Case Report: A 57-year-old man was hospitalized for fever of unknown origin, weight loss, and general fatigue, all of which were progressive and had appeared in a span of 6 months.　Physical examination revealed spiked fever and splenomegaly, but no lymphadenopathy or skin lesions.　Neurological examination revealed spastic paraparesis with sensory and urinary disturbances.　The levels of serum lactate dehydrogenase and soluble interleukin-2 receptor were 527 IU/L and 8,220 U/mL (normal range: 220-530, respectival), respectively.　Although IVL was strongly suggested, repeated bone marrow and muscle biopsies were negative.　Despite the presence of splenomegaly, his poor physical status did not allow a diagnostic splenectomy.　Six random biopsy specimens of healthy-appearing skin showed obliteration of small vessels in the subcutaneous fat tissue by lymphoma cells.　Chemotherapy, including rituximab, was successful, and the patient has survived with complete remission until now.

　Conclusion: Random skin biopsy is an extreme useful tool for the diagnosis of IVL.　The rate of positive diagnoses is high,since sufficient specimens can be obtained easily with little invasion.　To yield positive results,the biopsy should (i) target a visible skin lesion,if possible; (ii) include not only the dermis but also deeper layers,including the hypodermic adipose tissue; (iii) be relatively large; and (iv) should be performed at,at least,3 different locations such as the upper arm,thigh,and abdomen.