Description

A male patient in his early 70s presented with a 1-month history of progressive dyspnoea on exertion. His oxygen saturation was 94% on ambient air at rest but decreased to 82% when walking. Physical examination findings, including lung sounds, were normal. Laboratory tests revealed elevated serum lactate dehydrogenase at 752 U/L (reference: 124–222 U/L) and soluble interleukin-2 receptor at 1514 U/mL (reference: 122–496 U/mL). CT found no lung abnormalities (figure 1A), but 18F-fluorodeoxyglucose positron emission tomography (PET) CT revealed diffuse fluid accumulation in the bilateral lungs (figure 1B). A transbronchial lung biopsy performed in the right posterior regions (B2, B6, B9 and B10 segments) revealed CD3-negative and CD20-positive neoplastic lymphoid cells in the vessels (figure 2). Peripheral blood smears, a random skin biopsy and a bone marrow biopsy returned negative. Pulmonary intravascular large cell lymphoma was diagnosed. Following pola-R-CHP administration, his dyspnoea quickly resolved.

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

(A) Chest CT revealed no lymphadenopathy or CT abnormality in the lung fields. (B) Despite the normal CT findings. ¹⁸F-fluorodeoxyglucose PET/CT revealed diffuse, bilateral, right predominant, accumulation in the lung field. PET, positron emission tomography.

• Download figure
• Open in new tab
• Download powerpoint

Figure 2

(A) H&E staining of a specimen from a transbronchial lung biopsy showing CD3-negative and CD20-positive neoplastic lymphoid cells lodged in the vessels (arrows). (B) CD20 immunohistochemical staining showing positivity of the lymphoid cells for CD20.

Intravascular large cell lymphoma (IVCL) is extremely difficult to diagnose because of its rarity (incidence: 0.095/1 000 000),1 non-specificity of its symptoms and potential for rapid deterioration.2 Lymphoma cells in IVCL proliferate exclusively within the vasculature, making a definitive, histological diagnosis challenging. Organs that may be biopsied include the skin, bone marrow, liver, kidney, brain, gastrointestinal tract and lungs, depending on the patient’s symptoms and tests results.2 Furthermore, if respiratory symptoms, including progressive dyspnoea, are present, PET/CT should be considered before a transbronchial biopsy.2

The so-called ‘hot lung sign’ is defined as a mismatch between PET/CT findings of accumulation and normal CT findings (table 1).3 Although the evidence is insufficient, most previously reported cases of hot lung sign were ultimately diagnosed as IVCL, making the sign a quasi-pathognomonic index of ILCL and a useful guide to determining the biopsy site.3 In our case, the ¹⁸F-fluorodeoxyglucose uptake was bilateral but more pronounced in the right posterior region; therefore, a targeted, transbronchial biopsy was performed at the site with successful results.