Concurrent papillary thyroid carcinoma and incidental cervical lymph node indolent B cell non-Hodgkin lymphoma: clinicopathological features, outcomes, and potential relationships.

Objective: Concurrent cases of papillary thyroid carcinoma (PTC) and non-Hodgkin lymphoma are infrequent, especially when both are diagnosed simultaneously. This study aims to investigate the clinicopathological characteristics and immunophenotypic features, and clinical outcomes of patients diagnosed with both PTC and incidental cervical lymph node indolent B cell non-Hodgkin lymphoma (CLN-B-NHL), and to explore potential relationships between these two conditions.

Methods: A retrospective analysis was conducted on patients who underwent thyroid lobectomy and were diagnosed with PTC and incidental CLN-B-NHL based on final pathological assessments at a single cancer center from 2015 to 2018. Immunohistochemistry(IHC) staining for BCL-2 and Cyclin D1 was performed, followed by fluorescence in situ hybridization (FISH) for validation. Clinicopathological characteristics and treatment outcomes were systematically recorded and analyzed.

Results: The incidence of incidental CLN-B-NHL among 17,196 PTC patients was 0.04%. The cohort included 7 patients (3 males, 4 females; median age: 50 years), with 5 presenting asymptomatic thyroid/neck masses and 2 detected incidentally. All patients had PTC (American Joint Committee on Cancer, AJCC stage I), and 4 exhibited lymph node metastases. CLN-B-NHL subtypes included 5 follicular lymphomas (FL), 1 mantle cell lymphoma (MCL), and 1 nodal marginal zone lymphoma (NMZL). Notably, 3 patients had both PTC metastases and lymphoma within the same lymph node. IHC revealed weak BCL-2 expression in 4/7 cases of PTC and strong Cyclin D1 positivity in all 7 cases, contrasting with normal tissues. FISH analysis identified BCL2/IGH rearrangements in 4 FL cases and a CCND1/IGH translocation in 1 MCL case, but no such alterations were found in PTC. Treatment included R-CHOP in 4 cases and VR-CAP in 1 case, with 5 patients achieving complete remission and 2 achieving partial remission. The 5-year overall survival rate was 100%.

Conclusions: The concurrent diagnosis of PTC and indolent CLN-B-NHL is extremely rare, with distinct clinicopathological and immunophenotypic features. A subset of cases exhibited coexisting PTC metastases and lymphoma within the same lymph node, though no direct molecular link (e.g., shared BCL2/IGH or CCND1/IGH alterations) was identified. Despite favorable treatment responses and 100% 5-year survival rate in this cohort, the small sample size limits definitive conclusions regarding long-term outcomes. Comprehensive pathological evaluation is critical for PTC with atypical lymph node involvement, and further studies are needed to validate the role of aggressive management in this population.