Primary Bone Lymphoma of the Humerus (About A Case and Literature Review)

Background: Primary localised bone lymphoma is a rare affection prevalent in humans. It often involves long bones, but can be found in all the skeleton bones. The diagnosis is based on the anatomopathological study with immunohistochemical study of a bone biopsy. Case presentation: We also report the �rst diagnosed case of primary bone lymphoma of the humerus since the inauguration of our university hospital (since September 2014). Conclusions: It is an extremely rare pathology, of which the orthopedist must know. Treatment is based on chemotherapy (with or without anti-CD20) followed by radiotherapy. The prognosis of primary localised bone lymphoma is very favorable. Background:


Background:
The World Health Organization (WHO) de ned primary bone lymphoma in 2002 as a single bone lesion with or without regional lymph node involvement or multiple bone injuries without distant visceral or lymph node involvement [1].It is a rare entity, in fact primary bone lymphomas represent 1-3% of no Hodgkin's lymphomas, 5% of extra-ganglionic no Hodgkin's lymphomas and 3% of primary bone tumors [2,3].

Case Presentation:
H.Y, 77 years old, female, hypertensive, no insulinodependant diabetes, in good condition, who had been complaining for 1 month of mixed pains in his right arm without functional impotence or other associated signs.
The musculoskeletal examination did not reveal any mass in the arm or in ammatory signs, apart from a slight pain on palpation.The examination of the locoregional lymph node areas was without particularities, also the general somatic examination.
Standard radiographs of his right humerus showed a small lytic lesion of the external cortex of the humeral shaft without a periosteal reaction (Fig. 1).The TAP CT revealed the same lesion with no soft tissue extension (Fig. 2), no suspicious lesions on the thoraco-abdomino-pelvic views, and no lymphadenopathy.
The biological assessment did not reveal any anomalies, in particular a LDH concentration in the normal fork.
The patient underwent a bone biopsy, the immunohistochemical result of which was in favor of diffuse large B cell lymphoma (Fig. 3).
After a multidisciplinary concertation meeting, the patient is a candidate for 6 cures of CHOP chemotherapy combined with anti-CD20, and radiotherapy thereafter.

Discussion:
Primary bone lymphomas are de ned by the primary location of a malignant lymphoma in the bone, with a negative extension assessment within 6 months of the positive diagnosis.Another inclusion criterion is unique bone localization, but some authors integrate multifocal bone lymphomas into primary bone lymphomas [2].
Primary bone lymphomas are rare.They predominate in men of median age between 40-60 years [4,5].
The classi cation used for primary bone lymphoma is that of Ann Arbor, which distinguishes four stages Bone pain is the most frequently reported symptom (60-100%).Local swelling is found only in 50% of cases [6].A pathological fracture rarely reveals the disease (10-17% of cases) [1].Spinal cord compression is a symptom revealing of certain vertebral localizations [1,8].B symptoms are rarely seen [4].
The radiological appearance of primary bone lymphoma is variable and no speci c.It is often a destructive osteolytic lesion arising from the bone marrow.The lesion can be focal and well limited or cause a cortical rupture, a pathological fracture, or even extend to the soft tissue [4].
Bone scintigraphy often shows hyper xation of the tracer which is not speci c [4].MRI is more suitable for tumor evaluation.It typically shows a bone marrow replacement with a T1 hyposignal and a T2 hypersignal.MRI also makes it possible to study the extension to the soft tissue and to the spinal cord and to look for signs of compression [4].
The diagnosis is based on a bone biopsy with an anatomopathological and immunohistochemical studies [6].Primary bone lymphomas are no Hodgkin large B cell lymphomas in 80% of cases [3,4].They are often localized [3].
Radiotherapy was the standard curative treatment for primary bone lymphoma localized before the therapeutic combination area.Currently, chemotherapy followed by radiotherapy has demonstrated its interest in overall survival without relapse, and constitutes the reference treatment regimen [6,9].CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone) is the standard rst line treatment.The recommended number of cures is 3-8 [8, 9].There is likely to be no bene t from using more intensive chemotherapy such as ACVBP (doxorubicin, cyclophosphamide, bleomycin, vincristine and prednisone) [5,10].The literature data concerning the addition of anti-CD20 to chemotherapy are discordant [8,9].In case of response, consolidation radiotherapy is delivered in the initial tumor volume with a margin of 2 cm.A dose of 40-50 Gy in standard spreading and fractionation is recommended [4,6,8].In rare cases of no response to chemotherapy, there is no clear attitude in the literature.
Currently, the place of surgery in the management of primary bone lymphomas is limited.The initial surgical biopsy allows the diagnosis.The role of surgery comes down to the treatment of pathological fractures and threatening lesions of fracture or spinal instability [4].In case of spinal cord compression, a laminectomy is often decided to free the marrow and avoid the installation of an irreversible neurological de cit [11].
The prognosis of localized primary bone lymphomas is excellent.The survival probability at 5 years is at stage I of 90% [8].The IPI or international prognostic index (including age, general condition, stage, LDH concentration and number of lymph node areas affected) is an independent prognostic factor in terms of overall survival of patients with primary bone lymphoma [1,8].

Conclusion:
Primary localized bone lymphoma is a rare disorder prevalent in humans.It often involves long bones, but can be found in all the skeleton bones.The clinical presentation is not speci c.The diagnosis is based on the anatomopathological and immunohistochemical studies of a bone biopsy.Treatment is based on chemotherapy (with or without anti-CD20) followed by radiotherapy.The prognosis for primary localized bone lymphoma is very favorable.

Declarations:
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Figure 1 Front
Figure 1 [6].Primary bone lymphoma is at a localized stage if it is classi ed stage IE or IIE with no symptom B and without tumor mass greater than or equal to 10 cm (bulky).It is advanced if it is stage III, IV, IE or IIE with B symptoms or bulky [7].The most frequent anatomical sites are bones with signi cant hematopoietic activity (long bones, vertebrae, pelvis, ...) [6].Mandibular involvement represents 2-17% of published cases [8], the clavicle is reached in 4% of cases [8].