Lymphoblastic lymphoma (LL) constitutes a distinct clinicopathologic entity occurring most commonly in older children, adolescents, and young adults. LLs are mainly of the T-cell type, with only 10-20% being of the B-cell type. Unlike T-LL, pre-B LL predominantly presents with extranodal masses, especially those involving the skin with low propensity for leukemic involvement. Bone is the second most common site of extra-nodal involvement in T-LL. In this report we describe a patient who presented with multiple bone lesions as a primary site of symptomatic disease, but also with diffuse nodal, renal and pulmonary involvement.
A 11-year-old boy presented with progressive right shoulder and elbow pain and mild fewer and right supraclavicular and laterocervical lymphadenopathy.
In two hospitalizations he had been treated for suspected clavicular osteomyelitis , than for diffuse chronic sclerosing osteomyelitis. Right clavicle XRay showed mild disomogeneous structure of bone, thickened periostial in the site of myelitis. Echograpy of right elbow showed no alteration of subskin , tendons or intrarticular joint effusion . 99mTc-MDP three phases and whole body was not diagnostic for osteomyelitis showing multiple and symmetrical skeletal lesions and total involvement of clavicles and skull. In view of non-response to antibiotics, possibility of malignancy was considered. The boy underwent MRI resulting with bilateral cortical renal nodules , marrow cytology (negative for leukemia), 18FDG PET-Tc and chest CT which revealed bilateral lung small sites , right axillar and mediastinic adenopaty and confirmed bone localizations (clavicle, sternum, and scapula). Bone and lympho-nodal biopsies provided histological diagnosis of lymphoma lymphoblastic B (CD 99, vimentine, CD 10, CD79A, TdT, CD34, BCL2 positives); marrow and e CNS were negative, than the boy was enrolled in EURO-SLB 02 protocol. Interim Pet-CT showed a strong improvement in all sites with persistence of metabolic sites in femurs. Gadolinium-enhanced MR whole body demonstrated only some mediastinal end inguinal bilateral LN and some sites STIR-positive and DWIBS-negative of post-chemotherapy osteo-necrosis. After completing therapy he achieved a complete response, as confirmed by FDG-PET-CT. At present, the patient is in a good condition.
Precursor B-cell LL presenting with extensive skeletal involvement is rare. Clinically and histologically it may be confused with other small round cell tumors and infections. Hence, LL must be considered in the differential diagnosis of extensive bony lesions, and adequate immunohistochemical markers must be used to differentiate this entity.

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