Radiologic morphology of low-grade primary central nervous system lymphoma in immunocompetent patients

Abstract

Background and purpose: Primary central nervous system lymphomas (PCNSLs) are usually high-grade and are rarely low-grade non-Hodgkin lymphomas (NHLs). On MR imaging, PCNSLs typically present as contrast-enhancing lesions in contact with the subarachnoid space without evidence of necrosis. We evaluated the radiologic morphology and clinical characteristics of low-grade PCNSLs, hypothesizing that they may differ from high-grade PCNSLs.

Methods: Records were reviewed from 332 patients screened for inclusion in 3 multicenter prospective trials. MR imaging scans were obtained from all patients and were centrally reviewed by 2 consultant neuroradiologists.

Results: Ten patients (3%) with low-grade PCNSLs (7 men and 3 women; median age, 59 years; age range, 19-61 years) were identified. Four patients had one lesion, 2 patients 2 lesions, and 4 patients had multiple lesions. The following radiologic features infrequently seen in high-grade PCNSLs were found in a substantial proportion of patients: location in deep structures or spine (n = 6); lack of periventricular location (n = 5); hyperintensity on T2-weighted images (n = 10); moderate or absent contrast enhancement (n = 6); and heterogeneous contrast enhancement (n = 5). In 8 patients, >2 of these features were present in at least one lesion, and, thus, the radiologic appearance was assessed atypical of high-grade PCNSLs. The atypical radiologic appearance in combination with atypical or mild symptoms resulted in a false or delayed diagnosis.

Conclusion: Low-grade PCNSLs may have a variable and atypical radiologic morphology compared with high-grade PCNSLs with the risk of false or delayed diagnosis.

Fig 1.

Histologic preparations of low-grade PCNSLs (patient 9; lymphoplasmacellular lymphoma), opposed to high-grade PCNSLs. A, Infiltrates of small, mature lymphocytes surrounded by amorphous substance (immunohistologic demonstration of light-chain deposits) and absence of blastic, immature cells (hematoxylin and eosin; original magnification ×400). The lymphocytes are positive for the B-cell antigen CD20 and show a predominant expression of the immunoglobulin light chain lambda, indicating monoclonality (not shown). B, Typical appearance of high-grade PCNSL, composed of immature blasts with large and partly bean-shaped nuclei and prominent nucleoli (hematoxylin and eosin; original magnification ×400). C, Lymphoma cells of low-grade PCNSL demonstrate a low growth fraction of only 2% (Ki-67 antibody; original magnification ×200). D, High-grade PCNSL with a typical high growth fraction of 95% (MIB-1 antibody; original magnification ×400). Note.—Reproduced from K. Jahnke et al, Br J Haematol 2005;128:616–624 (© British Society for Haematology).

Fig 2.

Case 3, 60-year-old man with low-grade B-cell lymphoma (no further histologic specification). A, T2-weighted turbo spin-echo sequence. B, Precontrast T1-weighted spin-echo sequence. C, Postcontrast T1-weighted spin-echo sequence. On the precontrast T1-weighted image, the lymphoma (arrows) already demonstrates mild hyperintense spots, and only minor contrast enhancement is noted on the postcontrast T1-weighted sequence. In addition, on T2-weighted imaging, periventricular and basal ganglia edema is noted. Note.—Reproduced from K. Jahnke et al, Br J Haematol 2005;128:616–624 (© British Society for Haematology).

Fig 3.

Case 9, 19-year-old man with low-grade B-cell lymphoma (subtype lymphoplasmacellular lymphoma). A, Extensive hyperintense appearance of the lesion adjacent to the posterior aspect of the right lateral ventricle in FLAIR sequence. B and C, Surprisingly low contrast enhancement on T1-weighted imaging. Moderate edema is noted on T2-weighted imaging (not shown).

Fig 4.

Case 1, 58-year-old man with an intramedullary low-grade T-cell lymphoma. A, T2-weighted turbo spin-echo sequence. B, Postcontrast T1-weighted spin-echo sequence with 2 lymphoma manifestations, situated at the level of the cervicothoracic junction and the thoracic vertebrae 4 and 5 (arrows). Both lesions demonstrate pronounced local edema. The upper lesion shows a marked, homogeneous contrast enhancement, whereas the lower lesion demonstrates only mild contrast enhancement. This patient did not have cerebral lymphoma manifestations. Note.—Reproduced from K. Jahnke et al, Br J Haematol 2005;128:616–624 (© British Society for Haematology).

Fig 5.

Case 2, 58-year-old man with T-cell lymphoma. A right periventricular lesion with strong and homogeneous contrast enhancement is noted on T1-weighted postcontrast spin-echo sequence. Despite radiologic features typical of high-grade PCNSLs, histopathologic investigation revealed a low-grade PCNSL with a growth fraction of 1%.

Fig 6.

Case 10, 45-year-old man with low-grade B-cell lymphoma (no further histologic specification; arrows) with bifrontal hyperintense periventricular white matter lesions on A, T2-weighted, and B, FLAIR images. C, The lesions are not visible on T1-weighted precontrast imaging. D, No contrast enhancement is noted on the T1-weighted postcontrast section. E, This T2-weighted image additionally demonstrates a small area of hyperintensity located in the head of the corpus callosum.