The most common x-ray appearance is a ‘permeative lytic lesion with a wide transition zone’   

•        Non-specific Features
•        Bones may have a normal appearance

·       When lesions are evident they may be:

•    Lytic 
•    Sclerotic
•    Mixed             

Fig. 2: PATIENT 1: A 26 year old male presented with a 2 month history of painful left groin and limp without history of trauma. X-ray of pelvis demonstrates an osteolytic lesion in the left acetabulum and soft tissue swelling. MRI and CT PET were performed for further evaluation (figures 2 and 3).
References: Department of radiology, Beaumont Hospital

MRI Findings:

·       Bone marrow  

• T1 : Hypointense
• T2 : Hyper-intense/ Heterogenous/ mosaic pattern of bone marrow replacement  Fig. 3

·      Cortex

• Complete cortical destruction

·       Soft tissue

• Associated soft tissue masses

Fig. 3: PATIENT 1: T2 Fat sat MRI confirms a left lytic acetabular lesion extending into the superior ileum with cortical destruction.
References: Department of radiology, Beaumont Hospital

Fig. 4: PATIENT 1 : Fused axial PET image demonstrates increased uptake in the left acetabulum with no obvious disease elsewhere. CT guided biopsy of left acetabulum diagnosed a high grade B cell lymphoma. Diagnosis of primary lymphoma of bone.
References: Department of radiology, Beaumont Hospital

Secondary bone lymphoma occurs in 15% of disseminated lymphoma and is much commoner than primary lymphoma. It has similar clinical and imaging features to primary bone lymphoma or maybe discovered incidentally on staging the disease but it more commonly involves  the axial skeleton – spine, skull, facial bones, ribs and also the pelvis. 

Other examples of bone lymphoma are shown

• Patient 2 :  Fig. 5, Fig. 6, Fig. 7
• Patient 3:  Fig. 8,  Fig. 9
• Patient 4: Fig. 10,  Fig. 11

Skeletal muscle lymphoma is rare, accounting for <2% of lymphoma and predominantly occurs over the age of 60. It can be classified into primary or secondary muscular lymphoma. Primary muscular lymphoma is rare. It can affect any muscle but commonly presents in the thigh, forearm/arm and back.

Clinical presentation of lymphoma in muscle:

•        Pain
•        Swelling/mass
•        'B Symptoms'

Imaging features of lymphoma of musculoskeletal lymphoma

Fig. 12: PATIENT 5: 86 year old man presented with pain and swelling in his right upper arm. Plain x-ray showed a subtle lytic lesion in the humerus (horizontal arrow) with some cortical destruction. A soft tissue mass was also evident(sagittal arrows)
References: Radiology, Beaumont Hospital

MRI Findings:

•        Muscle enlargement
•        T1: Iso-intense/slightly hyperintense compared to normal muscle
•        T2: Intermediate signal intensity between muscle and fat
•        Post contrast enhancement: Homogenous band-like enhancement or septal enhancement
•        Long segmental involvement
•        Adjacent subcutaneous stranding +/- skin thickening

Fig. 13: PATIENT 5: T1-W MR shows a low signal marrow abnormality in the upper humerus (arrow) and a soft tissue mass in the triceps (asterisk)
References: Radiology, Beaumont Hospital

Fig. 14: PATIENT 5: Fat sat T2-W image shows high signal in the involved marrow with a wide zone of transition (arrow) and a mass in the soft tissues (asterisk). Note also the oedema in the soft tissues above and below the tumour. Biopsy confirmed diffuse large B cell lymphoma
References: Radiology, Beaumont Hospital

Other imaging examples of musculoskeletal lymphoma are shown

Patient 6:  Fig. 15,  Fig. 16,  Fig. 17

Patient 7:  Fig. 18, Fig. 19

Primary cutaneous lymphoma is defined as a lymphoid neoplasm confined to the skin without nodal or distal involvement.  Skin lymphoma is the commonest form of musculoskeletal lymphoma with an incidence of 1 in 100,000. 66% are cutaneous T cell lymphoma, 25% are cutaneous B cell lymphoma and the remainder are derived from natural killer cells. Mycosis fungoides is the commonest T cell lymphoma. It can present with scaly, red or purple papules, plaques, patches, nodules and tumours which may be associated with pruritus. 'B symptoms' may also be present.

Imaging characteristics of skin lymphoma

CT thorax abdomen and pelvis and FDG-PET is performed to assess for nodal or distal disease when staging skin lymphoma. Diagnosis is confirmed with skin biopsy of the lesion. 

CT

Imaging features are non-specific and may include:

• May have a normal appearance
• Multiple nodules / Plaque like thickening
• Mass
• Fat stranding
• Ulceration

Fig. 20: PATIENT 8: A 70 year old man presented with a 15 cm ulcerated and fungating mass in the left flank. Axial CT image shows the soft tissue mass with a large ulcer (arrow). There is irregular thickening and oedema with some fat stranding also seen. Biopsy confirmed an anaplastic T cell lymphoma
References: Radiology, Beaumont Hospital

Musculoskletal lymphoma can present in a variety of ways. A thorough history and examination is important to assess for clues such as regional pain and mass. Imaging findings as illustrated above, can provide the radiologist with clues that point toward musculoskeletal lymphoma but histology is ultimately required to obtain a definitive diagnosis. All patients with lymphoma should be discussed and managed in a multidisciplinary setting.

In lymphoma with primarily nodal disease, CT and FDG-PET is important for initial staging and to assess response to treatment using a staging system such as the Lugano classification, which is the most widely used. FDG-PET is preferable to CT for FDG avid nodal disease while CT is preferred for nodal disease that is does not have FDG-avid nodes. For patients with extra-nodal diffuse large B cell lymphoma of the musculoskeletal system, FDG-PET/CT is recommended.

Staging in the primary cutaneous T cell lymphomas mycosis fungoides and Sezary syndrome is unique. A CXR is the only imaging indicated if a comprehensive clinicial skin and lymph node exam stages the disease as T1 (Limited patches, papules, and/or plaques covering <10% of the skin surface) with absence of significant blood involvement (B0). All other stages require staging with CT thorax abdomen and pelvis +/- neck. FDG-PET may increase accuracy of staging but is not specifically part of the current staging criteria.