Hodgkin's Lymphoma of Bone

Primary bone lymphoma: Lymphoma of bone can present as primary lymphoma of bone (isolated to bone) or as a part of the disseminated disease. Diagnosis of primary bone lymphoma is based on lymphoma with a single bone lesion with or without regional nodal metastasis and the absence of distal lesion within six months of diagnosis [1]. When primary lymphoma of bone (PLB) present with multiple bone lesions it is considered as a sub group of PLB and termed multifocal primary lymphoma of bone [1]. In PLB primary sites of bone involvement are pelvis and appendicular skeleton, with femur and tibia being the most common. Multifocal PLB tends involve vertebrae more commonly than primary lymphoma of bone [1]. According to WHO classification lymphoma involving bone are categorized in to four groups. Group 1, lymphoma with single bone site with or without regional lymph node involvement. Group 2, lymphoma with multiple bone involvement but no visceral or nodal involvement. Group 3, Bone tumor with other visceral involvement or lymph nodes at multiple sites. Group 4, Lymphoma involve any other site and found to involve bone by bone biopsy [2]. Commonest presentation is prolong pain. The patients also can present with swelling of affected bone, loss of function and pathological fracture of involved bone. Mean age of presentation is 42 to 54 years with a slight male preponderance. Primary lymphoma of bone and multifocal osseous lymphoma commonly result from Non Hodgkin lymphoma and PBL due to Hodgkin lymphoma is very rare [1]. Favorable prognostic factors for survival are age younger than 40 years, lack of B symptoms, normal LDH levels and female gender [1]. Radiographic features of PBL are nonspecific. When the lesions are confined to bone marrow radiograph can be normal and may under estimate the extent of osseous involvement. Commonest presentation in radiograph is a lytic lesion. The lytic lesions can be well defined, or it may have a wide zone of transition with moth eaten or permeative type of destruction. Lesions with advance disease will have cortical destruction, periosteal reaction and extraosseous soft tissue extension [1]. Both malignant and benign conditions come into differential diagnosis of lytic type of PLB. In an adult patient other considerations are metastasis, chondroblastic osteosarcoma, multiple myeloma, plasmacytoma, osteomyelitis and giant cell tumor. In children the differential diagnosis includes Ewing sarcoma, primitive neuroectodermal tumor, eosinophilic granuloma and infection [1, 3]. Pure sclerotic lesions are rare and reported only in 2% of PLB cases and more frequently seen with Hodgkin lymphoma patients. Sclerotic lesions involving vertebra can give a classical presentation on radiography described as “Ivory vertebra” [4]. The Ivory vertebra sign is referred to as increase in opacity of a vertebral body that retains in its size and contours, with no change in the opacity and contour of the adjacent Intervertebral disks. Ivory vertebra sign can be seen in children and adults. It is much less common in children and is typically result in lymphoma, usually Hodgkin’s lymphoma and less frequently they can have osteosarcoma, metastatic neuroblastoma, medulloblastoma or osteoblastoma that involves a vertebral body and cause increase opacity. In adults many conditions can give rise to an ivory vertebra such as metastases from prostate and breast, carcinoid, Paget’s disease, lymphoma usually Hodgkin’s lymphoma and occasionally osteosarcoma [4]. Sclerosis can be related to fibrosis or it can develop following treatment with radiation or chemotherapy. Differential diagnosis of sclerotic bone lesions are osteosarcoma, metastasis (from prostate, breast), Paget’s disease and Sarcoidosis [1, 3]. Bone scan with 99Tc MDP is more effective in detecting multifocal osseous involvement than radiography but less effective in detecting marrow involvement without any bone remodeling. Bone scintigraphy is not specific for tumor as the tracer uptake will be shown in benign processes such as fractures [1]. CT is a better modality for assessing the cortical and trabecular destruction, periosteal reaction, sequestra and extra osseous extension. Bone destruction with relative sparing of the cortex is a feature favoring lymphoma over malignant and benign conditions such as osteosarcoma and eosinophilic granuloma. Extraosseous tumor spread with preservation of the cortex is seen in PLB and this is thought to be due to tumor spread through vascular channels of the cortex. This feature is demonstrated seen in tumors such as Ewing sarcoma and PNET [1]. MRI imaging has the advantage of detecting bone marrow that involved with lymphoma. The tumor shows low signal intensity on T1W and high signal on T2w sequences compared to muscle. Extraosseous soft tissue masses are low on T1W studies and high signal intensity on T2W sequences and shows diffuse and homogenous enhancement with contrast. Lymphoma is one of the few pathological processes that cross a joint space to involve contiguous bone structures. Infection is the commonest condition to cross joint and other tumors are chordoma, chondrosarcoma and metastases [1]. FDG PET is used in tumor staging and evaluating treatment response in patients with lymphoma. PET/CT is more sensitive and specific compared to contrast enhanced CT or PET alone [5].