European Journal of Nuclear Medicine and Molecular Imaging | 2021
Pulmonary tumor thrombotic microangiopathy: the role of a lung perfusion SPECT-CT study
Abstract
A 79-year-old man with clinical history of advanced prostate cancer was referred to our institution for worsening dyspnea. Cardiac ultrasound imaging showed enlarged right ventricle and severe pulmonary hypertension. Suspecting pulmonary embolism, a thorax/abdomen contrast-enhanced CT scan was performed with no evidence of thromboembolism (a, b) neither lung parenchymal alterations (c, d). Since this patient was affected by end-stage prostate cancer, pulmonary tumor thrombotic microangiopathy (PTTM) was hypothesized as the cause of the severe pulmonary hypertension. PTTM is characterized bymultiple microthrombi of cancer cells surrounded by fibrotic intimal cell proliferation and by vascular remodeling mediated by tumoral growth factors. It is more frequently associated with gastric adenocarcinoma and also with other neoplasms [1, 2]. It can cause severe pulmonary hypertension and right ventricular failure. The diagnosis is challenging as computed tomography (CT) findings are often unspecific [3], whereas conventional lung scintigraphy may reveal perfusion defects [4–6]. For this reason, our patient underwent a lung scintigraphy but planar images (e) showed irregular radiotracer distribution on both lungs without significant defects clearly referable to embolism. Conversely, SPECT-CT scan revealed multiple perfusion defects compatible with pulmonary embolism (f, g). It is wellestablished that SPECT-CT lung scintigraphy has higher diagnostic accuracy for detecting pulmonary embolism than traditional planar images. Moreover, the accompanying low-dose CT scan yields clinically relevant information [7, 8]. This is the first case of PTTM where SPECT-CT added diagnostic value detecting multiple defects not revealed by planar images due to intrinsic poor spatial resolution. Therefore, in this clinical setting, SPECT-CT imaging must be recommended to unmask small perfusion defects.