Primary Bone ALK Positive Anaplastic Large- cell Lymphoma: A Case Report

Wei Zheng Zhejiang Provincial People's Hospital Qiao qiao Yin Zhejiang Provincial People's Hospital Tian cheng Hui Bengbu Medical College Wen hao Wu Qingdao University Qing qing Wu Zhejiang Chinese Medical University Hai jun Huang Zhejiang Provincial People's Hospital Mei juan Cheng Zhejiang Provincial People's Hospital Yan Rong Zhejiang Provincial People's Hospital Yi cheng Huang Zhejiang Provincial People's Hospital HongYing Pan (  zw19931125@126.com ) Zhejiang Provincial People's Hospital

Primary bone lymphoma (PBL) is a subtype of lymphoma that exclusively affects skeletal tissue. The prevalence of PBL is estimated to be 3%-7% among primary bone tumors and less than 2% among all lymphomas in adults [4,5] . Among PBLs, diffuse large B-cell lymphoma (DLBCL) is the most common pathological type, accounting for approximately70%-80% of all PBLs [6][7][8][9] . The ALCL subtype of PBL is extremely rare (3%-5% of all PBLs) [10][11][12][13] , and it therefore remains unclear whether it is similar to ALCL in general or whether it is a subtype with unique clinical biological characteristics. Furthermore, the prognostic impact of ALK expression in ALCL with primary bone lesions is still under debate.
Due to the rarity of this disease, more relevant studies and case reports are needed. Herein, we report one rare case of primary bone ALK positive ALCL in a 66-year-old male.

Case Presentation
A 66-year-old man presented with a 1-month history of neck and shoulder pain and intermittent fevers.
His fevers had no clear pattern in timing or duration. His neck and shoulder pain was not sharp, with no neck and shoulder stiffness or limited movement and was relieved by nonsteroidal antiin ammatory drugs (NSAIDs). He reported a body weight loss of 5 kg in the past month and denied having night sweats, diarrhea, emesis, or appetite changes. His past medical history included diabetes and cervical spondylosis, and there was no family history of malignancy. The patient had taken cefuroxime for 3 days by himself without advice from the doctor. However, intermittent fevers of 37.7 °C-38.9 °C persisted. Therefore, the patient was admitted to a local community hospital and accepted 1 week of hospitalization. Pertinent initial labs included leukocytosis (12.71 × 10 9 /L, 80.2% neutrophils),elevated C- with moxi oxacin for 5 days. His temperature returned to normal and discharged. However, two days after leaving the hospital, the fever (up to 38.8 °C) returned, and his neck and shoulder pain were more worsen ,thus he was transferred to our hospital for further evaluation.
Electrocardiogram, serum protein electrophoresis, tumor markers, as well as abdomen and heart ultrasonography were normal. The trephine bone marrow biopsy showed hypocellularity,and the aspirate revealed granulocyte hyperplasia but no cellular atypia. Flow cytometry was negative for any atypical lymphocytes. Chest CT scan revealed local bronchiectasis in the upper left and right middle lobes, furthermore, the obviously osteolytic lesion in T10 vertebral body were also noted( Fig. 1).Because of neck and shoulder pain, a thoracic enhanced MRI was performed. It indicated T2 and T10 vertebrae bone destruction, suggesting evident malignancy (Fig. 2, panels a-b). Based on these ndings, he underwent a positron emission tomography (PET)-CT examination for further evaluation. On PET-CT, increased 18 Fuorodeoxyglucose (FDG) avidity involved the left sphenoid wing, the C4-5, T2, T10, L5, S1, and S5 vertebrae, the right humeral head, both sides of the humerus,the right proximal femur. These lesions were identi ed as hypermetabolic lesions with a maximum standard uptake value (SUV) of 18.64. Different degrees of bone destruction could be observed in corresponding sites, indicating lymphoma or multiple myeloma involvement (Fig. 2, panels c-f). No lymph node or extranodal site (such as lung, liver, spleen, etc.) lesion was identi ed. CT-guided biopsy of the T10 vertebral body was performed and the pathological diagnosis was ALCL. Microscopic examination showed the lesions vertebral body were in ltrated by pleomorphic tumor cells which have a scanty cytoplasm and hyperchromatic nucle.The neoplastic cells exhibit small-to medium-sized with irregular nuclei and abundant clear cytoplasm.Hallmark cells (horseshoe-shaped or doughnut cells) are present and Reed-Sternberg cell-like cell were also noted (Fig. 3, panels a-b). Immunohistochemistry showed the large atypical cells were positive expression of ALK (Fig. 3, panel c), CD3 (Fig. 3, panel d), CD30 (Fig. 3, panel e), as well as negative expression of CD2,CD5, CD7, CD4, CD8, CD10, CD19, CD79a, B-cell lymphoma-2, multiple myeloma-1, epithelial membrane antigen and pan-cytokeratin. The proliferative index (Ki-67) was approximately 60% (Fig. 3, panel f). Based on the above ndings, the nal diagnosis was made as primary bone ALCL, ALK-positive, stage IVB. The patient had already received four cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy, and we planned to repeat the biopsy and radiological examination after completion of the fth cycle of therapy.

Discussion And Conclusions
PBL is an uncommon extranodal disease that represents approximately 1-3% of the of lymphoma cases and is more common in males than in females (8:1). In 1928, Oberling rst described it as reticulum cell sarcoma [14] . Based on their series in 1939, Parker and Jackson [15] established PBL as a distinct clinical entity. According to the last version of the WHO classi cation of tumors of soft tissue and bone, PBL is de ned as a neoplasm composed of malignant lymphoid cells, producing one or more masses within the bone, without regional lymph node or distant extranodal involvement [16] .
It is di cult to diagnose PBL by clinical manifestations and common laboratory examination. Pain (82-92%) and swelling (34-45%) of the involved site are two of the most common clinical manifestations of PBL [8] ,.Other less common presentations include pathological fractures and systemic "B-type" symptoms such as fevers, weight loss, and night sweats. It can involve any skeletal site, and the axial skeleton is the most commonly involved site. PBL most commonly presents as osteolytic or osteoblastic lesions with disease involvement of the cortex and reactive periosteal changes [17] . Plain X-ray lms are the initial diagnostic test of choice, but they often underestimate the extent of the lesion. CT scans are useful for disease staging and delineating spinal lesions. MRI is helpful in demonstrating bone marrow and soft tissue involvement. In addition, the functional assessment of bone lesions using FDG-PET imaging plays an important role. Studies have shown that FDG-PET displays a higher speci city and sensitivity than conventional bone scintigraphy in identifying lymphomatous in ltration of skeletal tissue [18] .
Among the multiple testing modalities, bone biopsy and immunohistochemical studies remain essential for con rmation of PBL and for differential diagnosis. CT-guided percutaneous biopsy has proven to be a safe and reliable way to obtain su cient samples [19,20] . Microscopically, DLBCL is the most common histological subtype of lymphoma with primary or secondary skeletal involvement. It accounts for 70-80% of all bone lymphomas [6][7][8][9] , with rare to anecdotal occurrences of follicular, marginal zone, lymphoplasmacytic, anaplastic large-cell, natural killer/T-cell, Burkitt, and Hodgkin lymphomas [21,22] .Available data on primary bone ALCLs are currently rare. ALCLs with primary bone involvement ful ll the previously mentioned PBL de nition and show the typical immunohistochemical and molecular ndings noted in a few case reports in the literature. The main differential considerations of PBL include secondary osseous lymphoma, other subtypes of lymphoma (DLBCL, NK/T-cell lymphoma, Burkitt's, follicular and lymphoplasmacytic) [23] , osteosarcoma, metastases, Ewing sarcoma [24] , chronic osteomyelitis and granulomatous infection such as tuberculosis [25] .
The prognosis of patients with primary bone DLBCL is directly correlated with the stage of disease. The 5- year overall survival (OS) varies from 82% for patients with stage IE disease to 38% for patients with disseminated DLBCL with skeletal involvement. However, the prognosis of ALCL-type PBLs is controversial. Noh et al [26] collected twenty-two cases of ALCL with primary bone involvement and found that the ALCL type of PBL showed poor biological behavior compared with PBL (5-year OS was 43.1% and 62-76%, respectively). In addition, the expression of ALK-1 protein has been reported to be a favorable prognostic factor in conventional nodal ALCL, but Nagasaka et al [27] showed that ALK-1 positivity is not a favorable prognostic feature for patients with primary bone ALCL. Therefore, further studies investigating the clinical behavior and pathogenesis of primary bone ALCL are warranted.
Strategies such as chemotherapy, immunotherapy, surgery and radiotherapy have been used to treat primary bone ALCL, yet CHOP remains the most commonly used initial therapy. The addition of etoposide to CHOP (also known as CHOEP) improved outcomes for younger patients with ALK + ALCL (especially those with normal LDH levels at diagnosis) in a large retrospective meta-analysis (P < 0.04); however, the regimen was too toxic for older patients [28] . The infusional dose-adjusted etoposide, cyclophosphamide, doxorubicin, vincristine, and prednisone (EPOCH) protocol produced very encouraging outcomes in a single institution long-term prospective study that enrolled ALCL patients with high-risk features. After a median follow-up of more than 12 years, median survival for both ALK + and ALK-patients was not reached, with a 10-year OS rate of 75% [29] . On the basis of these results, CHOEP should be considered in younger patients with ALK + ALCL for initial therapy, while CHOP and da-EPOCH should be reserved for older or less t patients.

Recently, novel agents have emerged in the treatment of ALCL. Brentuximab vedotin (BV) is an anti-CD30
antibody-drug conjugate that selectively delivers an antimicrotubule agent, monomethyl auristatin E, into CD30-expressing cells. The initial phase 1 study conducted in patients with CD30-positive lymphomas, including ALCL, showed that BV treatment led to a response rate of 38%, including 11 complete remissions. The two patients with ALCL in the study achieved complete remission [30] . Subsequently, a phase 2 study in relapsed/refractory ALCL demonstrated an overall response rate of 86% and complete response (CR) rate of 57%. The median progression-free survival (PFS) was 13.3 months [31] . On the basis of these results, BV has been FDA-approved for relapsed/refractory ALCL following rst-line therapy. ALK inhibitors are also very promising because ALK tyrosine kinase activity is essential to the survival of ALK + ALCL cells. The oral ALK inhibitor crizotinib has demonstrated activity [32,33] . Crizotinib, an orally available dual ALK/MET inhibitor currently approved for advanced ALK + non-small-cell lung cancer (NSCLC) in adults, has been shown to induce high response rates: in a case series of nine patients with relapsed/refractory ALK + ALCL, all nine attained a CR following treatment with crizotinib [33] . The duration of response exceeded 30 months in some patients. With the constant development of novel agents, there may be profound modi cations in the therapeutic strategies for ALCL in the near future.
In summary, a rare case of primary bone ALK-positive ALCL is reported in this study. Physicians should keep in mind that ALCL can present with isolated osseous involvement without nodal involvement, and lymphoma should be considered in the differential diagnosis of primary bone lesions. For an accurate and prompt diagnosis, clinical features, PET-CT images, pathological histology and immunophenotype should all be considered.

Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Consent for publication
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editors-in-Chief of this journal.   (panels a-b).Thoracic enhanced MRI showed obvious T2 and T10 vertebral bone destruction (red arrows).
(panels c-f) .PET-CT showed increased 18F-uorodeoxyglucose (FDG) avidity involving the left sphenoid wing,the C4-5, T2, T10, L5, S1, and S5 vertebrae; the right humeral head, both sides of the humerus; and the right proximal femur. Multiple osteolytic lesions were identi ed as hypermetabolic lesions with a maximum standard uptake value (SUV) of 18.64; different degrees of bone destruction can be observed in corresponding sites (red arrows).