Benign lymphoid hyperplasia mimicking oligometastasis from non-small cell lung cancer after stereotactic ablative radiotherapy

Summary

Background: Benign lymphoid hyperplasia (BLH) is a rare lymphoproliferative disorder of normal polyclonal B lymphocytes, but is sometimes difficult to distinguish from malignancy. Case: An 87-year-old man with a history of localized non-small cell lung cancer (NSCLC) was referred for evaluation and treatment of an elastic hard tumor in the left supraclavicular fossa one year after stereotactic ablative radiotherapy (SABR). Whole-body PET scan showed high ¹⁸F-fluorodeoxyglucose uptake in the left supraclavicular fossa, and a dia­gnosis of oligometastasis was made. The tumor was homogeneously high signal on T2-weighted image with homogeneous enhancement after contrast administration. Since the palpation and MRI findings were inconsistent with those of metastatic NSCLC, a bio­psy was performed. Pathological and immunohistochemical investigation revealed the lesion to be BLH. Conclusion: In a patient with suspected oligometastasis after SABR for NSCLC, caution should be exercised before undergoing SABR for oligometastasis because BLH may be present.

Keywords:

oligometastatic disease – pseudolymphoma – stereotactic body radiotherapy – reactive lymphoid hyperplasia – lymph node metastasis

Introduction

Several studies have suggested that stereotactic ablative radiotherapy (SABR) is well tolerated and of clinical benefit for patients with oligometastatic non-small cell lung cancer (NSCLC) [1,2]. However, the dia­gnosis of oligometastases is generally based on noninvasive imaging findings. Therefore, accurate dia­gnosis of oligometastasis is an important factor in determining treatment and evaluating treatment efficacy. Here we report a case of NSCLC with a solitary hypermetabolic mass in the left supraclavicular fossa on positron emission tomography (PET), which was finally dia­gnosed as benign lymphoid hyperplasia (BLH) on pathological examination. As far as we know, this is the first case of NSCLC treated with SABR that subsequently developed BLH.

Case report

All procedures performed in this case report were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from the patient for use of clinical data in research.

An 87-year-old man was referred to our institution for evaluation and treatment of a palpable mass in the left supraclavicular fossa. His past medical history was unremarkable except for surgical resection for early-stage colon cancer three years ago, and SABR (60 Gy / 5 fractions) for stage IB NSCLC (adenocarcinoma, American Joint Committee of Cancer, 8th ed.) of the right upper lobe one year ago. Prior to SABR, there were no metastases on whole-body ¹⁸F-fluorodeoxyglucose (FDG) PET imaging (Fig. 1A). He had no recurrence without adjuvant therapy, but a painless elastic mass that was clinically unfixed appeared in the left supraclavicular fossa one year after SABR. Whole-body FDG-PET and PET/CT scan showed intense FDG uptake in the left supraclavicular fossa, but no other abnormalities were found (Fig. 1B, C). Maximum standardized uptake value (SUV_max) increased at 2 hours (4.52) compared to 1 hour (3.77) after FDG administration. CEA and CA 19-9 concentrations were within normal limits. Based on PET imaging findings, the patient was dia­gnosed with oligometastasis from NSCLC. Since there was no medical indication for systemic chemotherapy or immunotherapy, MRI-guided radiotherapy was planned. On MRI taken for radiation treatment planning, the tumor was homogeneously high signal on T2-weighted image (Fig. 1D), high signal on T1 map (Fig. 1E), and low signal on apparent diffusion coefficient from diffusion-weighted imaging (Fig. 1F). Post-gadolinium T1-weighted image demonstrated homogeneous enhancement of the tumor (Fig. 1G). Since the palpation and MRI findings were inconsistent with those of metastatic NSCLC, a core needle bio­psy was performed. Pathological and immunohistochemical investigation of the bio­psy specimen revealed the atrophic germinal center surrounded by concentric zones of lymphocytes (Fig. 1H), predominantly with CD20+ B cells. Based on the histopathological and immunohistochemical findings, a dia­gnosis of BLH was made. Since there was no recurrence of NSCLC, SABR was cancelled and followed up without treatment. The tumor of the left supraclavicular fossa gradually shrank and FDG uptake normalized one year after bio­psy (SUV_max 1.94: 2 hours).

Discussion

Oligometastasis is a type of metastasis in which cancer cells from the primary tumor travel through the body and form 1–5 metastatic lesions [3]. Studies have shown that aggressive treatment of NSCLC with oligometastasis improves overall survival compared to palliative approaches or immunotherapy alone [4]. SABR is one of the most effective treatments for oligometastatic disease, but standard dia­gnostic methods for each metastatic lesion have not been established. In general, the dia­g­­- nosis of oligometastases is made by noninvasive imaging, including whole-body PET, with little or no histopathologic examination. This case was initially dia­gnosed as oligometastasis from NSCLC by whole-body PET, but was later dia­gnosed as BLH by histopathology.

BLH is a rare disorder characterized by polyclonal lymphocytic infiltration predominantly with B lymphocytes, but the dia­gnosis of BLH is of clinical importance as it may be confused with malignant lymphoma or oligometastasis. FDG-PET can easily detect BLH, but its dia­gnostic accuracy is controversial [5]. Because of the rarity of this disease, there have been no well-organized studies investigating the dia­gnostic accuracy of FDG-PET. This case suggests the importance of routine physical examination and a multimodal dia­g­- nostic approach using PET and MRI for an accurate dia­gnosis of BLH. Although it is difficult to distinguish lymphoma from BLH by PET and/or MRI, it may be possible to rule out lymph node metastasis from NSCLC. Homogeneous hyperintensity of the tumor on T2-weighted image and T1 map with homogeneous enhancement after contrast agent administration, and the absence of central necrosis or hemorrhage are important clues to exclude metastases of NSCLC [6]. Elastic, unfixed lymph nodes on palpation are an adjunctive finding and are useful in the dia­gnosis [7].

Conclusion

In conclusions, a single case report cannot be generalized to others without further validation; however, a multimodal and multifactorial dia­gnostic approach would be warranted before performing SBRT for oligometastasis of NSCLC.

Funding

The authors received no financial support for the research and/or authorship of this article.

Authors‘ contributions

YH and ET designed the study, collected the data, and prepared the manuscript. Both authors approved the final version of the article.

Yukihiro Hama, MD, PhD
Department of Radiology
Edogawa Hospital
2-24-18 Higashikoiwa, Edogawa-ku,
Tokyo, 133-0052 Japan
e-mail: yjhama2005@yahoo.co.jp
Submitted/Obdrženo: 27. 3. 2022
Accepted/Přijato: 10. 5. 2022