A case of complete remission of Hodgkin lymphoma confirmed histopathologically by neck dissection

Abstract Background Hodgkin lymphoma (HL) is diagnosed definitively by biopsy, and treatment is based on stage. Owing to the nature of the disease, post‐treatment efficacy is determined mainly by fluorodeoxyglucose‐positron emission tomography/computed tomography, and the efficacy of treatment is not confirmed by histopathology. We report a case of tongue cancer after treatment for HL, in which a post‐treatment lymph node with complete remission was histopathologically confirmed by neck dissection. Case The patient was a 74‐year‐old man who was referred to our hospital for cancer on the right side of his tongue. He had previously undergone chemotherapy for HL involving the right side of his neck and achieved complete remission. Because he had cT3N2cM0 tongue cancer, glossectomy and bilateral neck dissection were performed. Surprisingly, histopathological examination revealed that there was neither metastatic lymph nodes nor lymphoma cells in his right neck. Moreover, there was no lymphatic structure in his remnant lymph nodes. Conclusion This was a rare case in which complete remission of HL was confirmed by histopathological analysis. The absence of lymph node structure and lymphatic flow led to contralateral neck lymph node metastases of tongue cancer.


| INTRODUCTION
Hodgkin lymphoma (HL) is a malignant disease of the lymphatic system. Overall survival rates for HL vary by age, race, and stage, but generally, the reported 5-and 10-year survival rates are 83.0% and 78.1%, respectively. 1 HL is diagnosed definitively by biopsy, and treatment is based on stage. Owing to the nature of the disease, posttreatment efficacy is determined mainly by fluorodeoxyglucosepositron emission tomography/computed tomography (FDG-PET/CT), 2 and the efficacy of treatment is not confirmed by histopathology. Therefore, the pathological findings of lymph node involvement after treatment of HL are unclear, and no related reports have been published, to our knowledge. There are no reports showing the pathological structure of HL that has gone into remission with treatment, and there is almost no opportunity for pathological confirmation of HL because of the nature of the disease and treatment. We report a rare case of complete remission in HL, as confirmed histopathologically by neck dissection.

| CASE REPORT
The patient was a 74-year-old man. He was referred to the Head and Neck Cancer Center, Iwate Medical University Hospital, in May 2021, because tongue cancer was suspected. He developed HL 1 year and 5 months prior to his first visit to our center. The pathological findings of HL were as follows: hematoxylin-eosin staining of the lymph nodes showed solitary or small clusters of atypical cells with rather large, irregular nuclei in the paracortical region ( Figure 1A). Immunohistologically, the atypical cells were cluster of differentiation 30-positive.
F I G U R E 1 Histopathological findings of Hodgkin lymphoma with previous chemotherapy. Hematoxylin-eosin (H-E) staining of the lymph nodes showing solitary or small clusters of atypical cells with rather large, irregular nuclei in the paracortical region (A: Â200). Immunohistologically, the atypical cells were CD30-positive (B: Â100). Strong positivity for PAX5 is also seen in the background B-cells, with weak positivity in the tumor cells (C: Â100). CD30, cluster of differentiation 30.
F I G U R E 2 Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) findings before and after HL treatment. The HL-affected areas were the right neck, right supraclavicular fossa, right pulmonary apex, right pulmonary hilum, right fifth posterior rib, and mediastinum. The image of the right neck shows abnormal accumulation of FDG with a maximum standardized uptake value (SUV max ) of 15.7. The mediastinum shows abnormal accumulation with an SUV max of 3.4 (A). HL was in complete remission (B). HL, Hodgkin lymphoma.   Figure 2B). Blood examination at the initial visit to our center did not identify abnormal findings (Table 1) Postoperative histopathological examination revealed that the tongue cancer was radically resected, and one metastatic lymph node of squamous cell carcinoma at left level IB and three nodes at left level III were found, none of which showed extranodal extension ( Figure 4A).
Additionally, the right cervical lymph node, which was in remission after Histopathologically, the cervical lymph nodes on the affected side in our case showed no normal lymph node structure. The interior part of these lymph nodes showed vitreous degeneration, which suggested that lymphatic flow may have been blocked; thus, no lymph node metastasis was seen. It is likely that the previous chemotherapy for HL, which involved a primary lesion in the right cervical lymph nodes, caused degeneration of the lesion and blocked normal lymph flow. Fortunately, in this case, we were incidentally able to explore and examine the histopathological findings after remission of HL. These data may be valuable because to our knowledge, there have been no previous reports showing the pathological findings or evaluation of foci that have achieved remission status with chemotherapy for HL. There have been reports of cases of recurrent HL controlled with intense chemotherapy, confirmed by FDG-PET/CT. 7 The usefulness of biomarkers, such as thymus and activation-regulated chemokine as prognostic and treatment monitoring for HL has also been reported. 8,9 We hope that this report of the pathology after HL treatment will contribute to the correlation of the pathological findings of the lymph nodes of remission cases and image monitoring, such as with FDG-PET/CT, in the future.

| CONCLUSION
In this case, because of the development of metastatic cervical lymph nodes from the tongue cancer, we performed dissection of the neck (in which the cervical lymph nodes were the main lesion) after treatment for HL. This allowed for histopathological identification of a lymph node that lost all normal structure after treatment for HL. This is a valuable case report demonstrating changes in the lymph node structure after HL treatment.