
==== Front
Clin Case Rep
Clin Case Rep
10.1002/(ISSN)2050-0904
CCR3
Clinical Case Reports
2050-0904
John Wiley and Sons Inc. Hoboken

10.1002/ccr3.9412
CCR39412
CCR3-2024-03-0753.R2
Health Informatics
Hematology
Case Report
Case Report
Diffuse large B‐cell lymphoma with BRAF V600E mutation mimicking thyroid carcinoma in fine‐needle aspiration: A diagnostic pitfall
Xu et al.
Xu Liming 1
Huang Dong Dong 1
Wang Jinghan 2
You Qihan 1
Yu Fang https://orcid.org/0009-0004-2747-3972
1 3311002@zju.edu.cn

1 Department of Pathology, The First Affiliated Hospital Zhejiang University School of Medicine Hangzhou China
2 Department of Haematology, The First Affiliated Hospital Zhejiang University School of Medicine Hangzhou China
* Correspondence
Fang Yu, Department of Pathology, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Shangcheng District, Hangzhou 310003, China.
Email: 3311002@zju.edu.cn

04 9 2024
9 2024
12 9 10.1002/ccr3.v12.9 e941224 7 2024
16 3 2024
12 8 2024
© 2024 The Author(s). Clinical Case Reports published by John Wiley & Sons Ltd.
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

Key Clinical Message

We report a rare case of thyroid diffuse large B‐cell lymphoma with a BRAF V600E mutation, which mimics poorly differentiated thyroid cancer in fine needle aspiration cytology.

Reasoning diagnostic features

BRAF V600E
DLBCL
FNA
NGS
source-schema-version-number2.0
cover-dateSeptember 2024
details-of-publishers-convertorConverter:WILEY_ML3GV2_TO_JATSPMC version:6.4.8 mode:remove_FC converted:05.09.2024
Xu L , Huang DD , Wang J , You Q , Yu F . Diffuse large B‐cell lymphoma with BRAF V600E mutation mimicking thyroid carcinoma in fine‐needle aspiration: A diagnostic pitfall. Clin Case Rep. 2024;12 :e9412. doi:10.1002/ccr3.9412
==== Body
pmc1 INTRODUCTION

The BRAF V600E mutation is the most prevalent genetic alteration in papillary thyroid carcinoma (PTC), leading to aberrant cellular proliferation and carcinogenesis through activation of the MAPK/ERK pathway. 1 However, the BRAF gene mutations are not limited to thyroid cancer. It has a varied frequency in hairy cell leukemia, melanoma, low‐grade ovarian cancer, colorectal cancer, nodal marginal zone lymphoma, and diffuse large B‐cell lymphoma (DLBCL). 2 Here we report a case of thyroid DLBCL misdiagnosed as poorly differentiated carcinoma due to BRAF V600E mutation in preoperative fine needle aspiration cytology (FNAC).

2 CASE HISTORY/EXAMINATION

A 65‐year‐old man was referred to our hospital with a painless right thyroid mass. There was no family history of thyroid or parathyroid disease. At the presentation, he denied B‐symptoms. Relevant physical examination findings were presented by a flowchart (Figure 1).

FIGURE 1 Relevant physical examination findings, diagnosis, and therapy.

3 METHODS (DIFFERENTIAL DIAGNOSIS, INVESTIGATIONS, AND TREATMENT)

Laboratory studies showed normal thyroid function, normal serum calcium and calcitonin levels and thyroid antibodies were negative. B‐ultrasonography revealed a hypoechoic nodule measuring 4.6 × 3.3 × 2.9 cm (EU‐TI‐RADS 4a) with well‐defined borders. The internal echoes are homogeneous, and enhanced posterior echoes were presented (Figure 2A). In addition, multiple enlarged lymph nodes were identified in the IV region of the cervical compartments. FDG‐PET/CT showed a large low‐density mass with increased FDG metabolism in the right lobe of the thyroid, which extended to the thoracic entrance approaching the esophagus. Multiple lymph nodes around the right lobe of thyroid gland also showed increased FDG metabolism. Given these imaging findings, a malignant neoplasm of thyroid origin with lymph node metastasis was considered.

FIGURE 2 Reasoning diagnostic features. (A) B‐ultrasonography revealed a hypoechoic nodule with well‐defined borders, with an enhanced posterior echo. (B) Papanicolaou‐stained smears of fine‐needle aspiration cytology (FNAC) showed high density of large monotonous atypical cells. (C) Amplification refractory mutation system PCR (ARMS‐PCR) showed BRAFV600E mutation in both FNAC and subsequent excision specimen. (D) Hematoxylin and eosin (H&E) staining of subsequent excision specimen showed diffuse proliferation of atypical round cells with vesicular chromatin and prominent nucleoli, which are positive for CD20 (E) and Ki‐67 (F).

FNAC was performed and showed tumor cells were clustered or singly dispersed. At high magnification, high density of large monotonous atypical cells had scant to moderate cytoplasm, ovoid nuclei, vesicular chromatin, prominent nucleoli, and frequent mitotic figures (Figure 2B). Nuclear features of papillary carcinoma are not obvious. BRAF V600E mutation was detected by amplification refractory mutation system PCR (ARMS‐PCR) (Figure 2C). Given the morphology and BRAF mutation, thyroid poorly differentiated carcinoma was considered.

Next, total thyroidectomy and cervical lymph node resection were performed. Gross examination of thyroid specimen revealed a grayish‐yellow soft mass that was 5 × 3.8 × 2.8 cm in size, with clear boundaries, close to the capsule. Microscopic examination showed sheets of atypical round cells with vesicular chromatin and prominent nucleoli (Figure 2D). By immunohistochemistry, they were positive for CD20 (Figure 2E), CD19, BCL‐6, MUM1, c‐Myc and Ki‐67 (Figure 2F), and negative for CD3, CD5, CD10, CD30, BCL‐2, and pan‐cytokeratin. The morphologic and immunophenotypic findings are diagnostic for DLBCL involving thyroid glands and lymph nodes. Subsequent next‐generation sequencing of the resection specimen identified several mutations, as shown in Table 1. The proteins encoded by these mutated genes were found to interact with each other by STRING protein–protein interaction networks functional enrichment analysis (Figure 3).

TABLE 1 Tumor‐specific mutations detected by NGS and their protein functions.

Gene	Location	Mutation	Nucleotide change	Percentage	Protein function	
B2M	Exon 1	p.Q22* nonsense mutation	c.64C > T	17.30	T‐cell modulation in pancreatic cancer	
BRAF	Exon 15	p.V600E missense mutation	c.1799 T > A	18.39	B‐cell receptor signaling pathway	
CARD11	Exon 6	p.D230N missense mutation	c.688G > A	14.77	Modulators of TCR signaling and T‐cell activation; B‐cell receptor signaling pathway; T‐cell receptor signaling pathway	
FAS	Intron 7	c.652‐1G > T shear mutation	c.652‐1G > T	13.65	T‐cell modulation in pancreatic cancer; T‐cell receptor signaling pathway	
GNA13	Exon 2	p.W153* nonsense mutation	c.459G > A	10.73	Modulators of TCR signaling and T cell activation	
ID3	Intron 1	c.300 + 1G > A shear mutation	c.300 + 1G > A	20.53	NA	
ID3	Exon 1	c.212_301‐30del shear mutation	c.212_301‐30del	11.75	NA	
TET2	Exon 3	p.G773* nonsense mutation	c.2317G > T	17.11	NA	
B2M	Exon 2	p.C45Y missense mutation	c.134G > A	15.40	T‐cell modulation in pancreatic cancer	
BCL10	Exon 3	p.S170* nonsense mutation	c.509_548del	2.06	Modulators of TCR signaling and T‐cell activation; B‐cell receptor signaling pathway; T‐cell receptor signaling pathway	
CARD11	Exon 9	p.D401N missense mutation	c.1201G > A	2.42	Modulators of TCR signaling and T‐cell activation; B‐cell receptor signaling pathway; T‐cell receptor signaling pathway	
CD274	Exon 4	p.T196P missense mutation	c.586A > C	21.26	T‐cell modulation in pancreatic cancer	
GNA13	Exon 1	p.I70N missense mutation	c.209 T > A	19.82	Modulators of TCR signaling and T‐cell activation	
NOTCH1	Exon 28	p.L1767F missense mutation	c.5299C > T	16.86	NA	
ROS1	Exon 38	p.R2042Q missense mutation	c.6125G > A	13.97	NA	
SGK1	Exon 6	p.P172S missense mutation	c.514C > T	13.25	NA	
SGK1	Exon 8	p.G276D missense mutation	c.827G > A	7.81	NA	
SGK1	Exon 9	p.F280L missense mutation	c.840C > G	4.25	NA	
* Denotes a stop codon (nonsense mutation), meaning that the amino acid at the position has been replaced by a premature stop codon.

FIGURE 3 Network showed the interaction among the proteins encoded by the mutated genes in the case, which was analyzed by STRING protein–protein interaction networks functional enrichment analysis.

4 CONCLUSION AND RESULTS (OUTCOME AND FOLLOW‐UP)

Lugano staging classification for this patient's DLBCL was stage IIE, with a score of 2 on the International Prognostic Index (IPI). 3 , 4 The patient achieved complete response after six rounds of R‐CHOP (rituximab + cyclophosphamide + doxorubicin + vincristine + prednisone) chemotherapy.

5 DISCUSSION

Primary thyroid lymphoma (PTL) is rare, accounting for approximately 5% of all thyroid malignancies and less than 3% of all extranodal lymphomas. 5 It is difficult to distinguish from poorly differentiated thyroid carcinoma (PDTC) on cytology as they share many similar cytologic features, such as hypercellular tumor cells with scant cytoplasm, variable nuclear atypia, and architectural atypia in the form of crowded groups and singly dispersed forms. The identification of mitotic figures, apoptotic bodies, and necrotic debris on cytology preparations, together with radiologic evidence of invasive growth may trigger the consideration of PDTC in the differential diagnosis. 6

FNAC is the preferred choice for initial evaluation of a thyroid lesion. Advances in detecting molecular alterations in FNA specimens may help diagnosing uncertain cases. BRAF and RAS point mutations and RET/PTC and PAX8/PPARγ rearrangements are the most common genetic alterations found in thyroid cancer and have been used for cancer detection in thyroid nodules with indeterminate FNAC. 7 BRAF is an initiator mutation, with common valine‐to‐glutamate substitution at residue 600 (V600E) detected in about 60% of PTCs, in particular tall cell variant, followed by PTC‐derived PDTC (12%–33%) and anaplastic thyroid carcinomas (25%–29%). 8 , 9 On the other hand, they are very rare in other thyroid lesions, such as medullary carcinoma, follicular carcinoma, and benign neoplasms. 10 In a systemic review and meta‐analysis evaluating the diagnostic utility of BRAF V600E mutation in indeterminate nodules, the overall sensitivity and specificity was 0.40 (95% CI: 0.32–0.48) and 1.00 (95% CI: 0.98–1.00), respectively. 11 BRAF V600E mutation has been recognized as an effective diagnostic marker in refining the risk of malignancy in patients with indeterminate nodules. However, the BRAF gene mutations are not limited to thyroid cancers.

BRAF mutations are reported in about 7% of solid tumors, with a high prevalence in melanoma (40%–60%), colorectal cancer (10%), and lung cancer (1.5%–8%). 10 , 12 , 13 Of concern, the hematolymphoid tumors that may occur in thyroid were also identified with BRAF mutations, such as hairy cell leukemia (approximately 100%), Langerhans cell histiocytosis (up to 65%), DLBCL (2.4%–6%), and thyroid DLBCL (24%). 14 , 15 , 16 , 17 , 18 , 19 In the case we reported, a rare BRAF V600E mutation was detected by ARMS‐PCR in FNA specimen, which was further confirmed by next‐generation sequencing in the subsequent resection specimen. Other non‐V600E mutations of D594G, K601N, G468A, G468R and D593G have also been reported in the literature. 18 , 19 That is, genetic mutation associated with thyroid cancer also occur in thyroid lymphoma. Therefore, the interpretation of finding BRAF mutations in thyroid FNAC must take into account the differential diagnosis of DLBCL. More recent studies have shown improvement in the accuracy of FNA when combined with immunophenotyping, especially for thyroid DLBCL patients. 20 However, when low‐grade mucosa‐associated lymphoid tissue lymphoma is suspected, core needle aspiration or surgical biopsy is still required, as it is often difficult to differentiate from thyroiditis. 21 Indeed, a rapidly enlarging neck mass and enhanced posterior echoes by B‐ultrasonography should raise suspicion for PTL. 22 It is important to advise the pathologist if there is suspicion for PTL, so that appropriate immunophenotypic analysis can be done. If the diagnosis of PTL can be confirmed, extensive surgical excision can be circumvented, and chemotherapy combined with radiotherapy may be employed in lieu of surgical intervention. 23

The mechanism of pathogenesis of thyroid DLBCL is largely unknown. In the case reported here, several nonsense mutations (B2M, GNA13, TET2, and BCL10), missense mutations (BRAF, CARD11, B2M, CD274, GNA13, NOTCH1, ROS1, and SGK1), and shear mutations (FAS and ID3) were detected. The proteins encoded by these mutated genes were found to interact with each other by STRING protein–protein interaction networks functional enrichment analysis. Their functions could be classified as: T‐cell modulation in pancreatic cancer (CD274, B2M, and FAS), modulators of TCR signaling and T‐cell activation (CARD11, GNA13, and BCL10), B‐cell receptor signaling pathway (CARD11, BRAF, and BCL10), and T‐cell receptor signaling pathway (CARD11, BCL10, and FAS). BRAF mutation appears to bridges the mitogen‐activated protein kinase pathway and some thyroid DLBCL pathogenesis, indicating a potential therapeutic target for thyroid DLBCL patients.

AUTHOR CONTRIBUTIONS

Liming Xu: Methodology; writing – original draft. Dong Dong Huang: Methodology; resources. Jinghan Wang: Data curation; software. Qihan You: Validation. Fang Yu: Project administration; supervision; writing – review and editing.

FUNDING INFORMATION

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

CONFLICT OF INTEREST STATEMENT

The authors declare that they have no competing interests in relation to this study.

CONSENT

Written informed consent was obtained from the patient to publish this report in accordance with the journal's patient consent policy.

DATA AVAILABILITY STATEMENT

All data generated or analyzed during this study are included in this article.
==== Refs
REFERENCES

1 Silver JA , Bogatchenko M , Pusztaszeri M , et al. Mutation is associated with aggressive features in papillary thyroid carcinomas ≤1.5 cm. J Otolaryngol Head Neck Surg. 2021;50 :63.34742355
2 Machnicki MM , Stoklosa T . BRAF—a new player in hematological neoplasms. Blood Cell Mol Dis. 2014;53 :77‐83.
3 Ruppert AS , Dixon JG , Salles G , et al. International prognostic indices in diffuse large B‐cell lymphoma: a comparison of IPI, R‐IPI, and NCCN‐IPI. Blood. 2020;135 :2041‐2048.32232482
4 Cheson BD , Fisher RI , Barrington SF , et al. Recommendations for initial evaluation, staging, and response assessment of Hodgkin and non‐Hodgkin lymphoma: the Lugano classification. J Clin Oncol. 2014;32 :3059‐3068.25113753
5 Lee JS , Shin SJ , Yun HJ , et al. Primary thyroid lymphoma: a single‐center experience. Front Endocrinol. 2023;14 :1064050.
6 Alwelaie Y , Howaidi A , Tashkandi M , et al. Revisiting the cytomorphological features of poorly differentiated thyroid carcinoma: a comparative analysis with indeterminate thyroid fine‐needle aspiration samples. J Am Soc Cytopathol. 2023;12 :331‐340.37302972
7 Ohori NP , Nishino M . Follicular neoplasm of thyroid revisited: current differential diagnosis and the impact of molecular testing. Adv Anat Pathol. 2023;30 :11‐23.36102526
8 Singh A , Ham J , Po JW , Niles N , Roberts T , Lee CS . The genomic landscape of thyroid cancer tumourigenesis and implications for immunotherapy. Cells. 2021;10 (5 ):1082.34062862
9 Nikiforova MN , Kimura ET , Gandhi M , et al. BRAF mutations in thyroid tumors are restricted to papillary carcinomas and anaplastic or poorly differentiated carcinomas arising from papillary carcinomas. J Clin Endocrinol Metab. 2003;88 :5399‐5404.14602780
10 Pisapia P , Pepe F , Iaccarino A , et al. BRAF: a two‐faced Janus. Cells. 2020;9 (12 ):2549.33260892
11 Jinih M , Foley N , Osho O , et al. BRAF(V600E) mutation as a predictor of thyroid malignancy in indeterminate nodules: a systematic review and meta‐analysis. Eur J Surg Oncol. 2017;43 :1219‐1227.27923591
12 Hayward NK , Wilmott JS , Waddell N , et al. Whole‐genome landscapes of major melanoma subtypes. Nature. 2017;545 :175‐180.28467829
13 Sanz‐Garcia E , Argiles G , Elez E , Tabernero J . BRAF mutant colorectal cancer: prognosis, treatment, and new perspectives. Ann Oncol. 2017;28 :2648‐2657.29045527
14 Tiacci E , Trifonov V , Schiavoni G , et al. Mutations in hairy‐cell leukemia. N Engl J Med. 2011;364 :2305‐2315.21663470
15 Kobayashi M , Tojo A . Langerhans cell histiocytosis in adults: advances in pathophysiology and treatment. Cancer Sci. 2018;109 :3707‐3713.30281871
16 Gray JCR , Kim J , Digianvittorio M , et al. BRAF‐mutated Erdheim–Chester disease: profound response to vemurafenib visualized with serial multimodality imaging. J Natl Compr Cancer Netw. 2020;18 :650‐655.
17 Chapuy B , Stewart C , Dunford AJ , et al. Molecular subtypes of diffuse large B cell lymphoma are associated with distinct pathogenic mechanisms and outcomes. Nat Med. 2018;24 :679‐690.29713087
18 Lee JW , Yoo NJ , Soung YH , et al. BRAF mutations in non‐Hodgkin's lymphoma. Br J Cancer. 2003;89 :1958‐1960.14612909
19 Aggarwal N , Swerdlow SH , Kelly LM , et al. Thyroid carcinoma‐associated genetic mutations also occur in thyroid lymphomas. Mod Pathol. 2012;25 :1203‐1211.22575864
20 Matsuzuka F , Miyauchi A , Katayama S , et al. Clinical aspects of primary thyroid lymphoma: diagnosis and treatment based on our experience of 119 cases. Thyroid. 1993;3 :93‐99.8369658
21 Stein SA , Wartofsky L . Primary thyroid lymphoma: a clinical review. J Clin Endocrinol Metab. 2013;98 :3131‐3138.23714679
22 Ota H , Ito Y , Matsuzuka F , et al. Usefulness of ultrasonography for diagnosis of malignant lymphoma of the thyroid. Thyroid. 2006;16 :983‐987.17042683
23 Yi JN , Yi PY , Wang W , et al. A multicenter retrospective study of 58 patients with primary thyroid diffuse large B cell lymphoma. Front Endocrinol. 2020;11 :542.
