Presentation
6 months of painful right mid-shin lump
Patient Data
Diffuse region of cortical thickening involving the medial aspect of the middle third of the tibial shaft. No focal lytic or sclerotic lesions visible.
Extensive signal abnormality within the shaft of the right tibia 17 cm in length, ranging from 7 cm inferior the tibial plateau to 11 cm superior to the ankle joint (coronal, sagittal).
The abnormal signal is heterogenous in intensity throughout the medullary cavity. It is hypointense on T1-weighted imaging, and hyperintense on T2-weighted and post-contrast imaging.
Aggressive periosteal reaction is noted anteriorly, with soft tissue enhancement extending into the subcutaneous fat over the anterior tibial aspect (axial, sagittal). A small periosteal fluid collection is noted along the anterior cortical margin.
The signal abnormality extends medially abutting the flexor digitorum longus muscle, but without definite extension into the muscle belly itself.
Normal marrow signal in the right fibula, as well as the left tibia and fibula.
Conclusion
Appearance consistent with an aggressive neoplastic process, most likely a primary tumour arising from the tibia. In this age group, osteosarcoma is favoured.
A permeative, destructive lesion is seen in the right tibial shaft (axial, coronal, sagittal) with invasion of the medullary cavity. The hypermetaboolic component (SUVmax 5.9) is 6cm in length.
Corresponding cortical irregularity and intra-medullary involvement is noted on the plain CT (axial, coronal, sagittal).
No other local or distant focal FDG-avidity is detected.
Histopathology
Sections show fragments of bone with sclerotic fibrous tissue containing some oval and round cells with scant cytoplasm and some spindling. There is some reactive bone formation.
Immunohistochemistry
Tumour cells appear to positively stain for LCA and CD20, as well as CD10 and CD79a, indicating a high proportion of immature B-cell lymphoblasts. Occasionnal cells show positive staining for bcl-2 and bcl-6. The sample is negative for MUM1, MPO, and TdT.
Conclusion
Changes highly suggestive of diffuse large B-cell lymphoma
Case Discussion
This 20-year-old man presented with a 6 month history of a painful right shin lump. Initial plain film of the leg revealed cortical thickening of the tibial midshaft but no clear focal lesions.
MRI demonstrated an aggressive and diffuse lesion involving both the cortex and medulla of the right tibia. PET-CT reflected the aggressive nature of this lesion but showed no other local or distant FDG-avid disease.
At this stage the most likely diagnosis was thought to be a primary bone malignancy, most likely osteosarcoma with differentials of Ewing's sarcoma and adamantinoma. The possibility of above-knee amputation was discussed.
CT-guided biopsy was performed and histopathology revealed unequivoccal diffuse large B-cell lymphoma (DLBCL) of the tibia. In the context of a single extra-nodal site of disease, stage 1E osteolymphoma was diagnosed.
The patient underwent 4 cycles of R-CHOP chemotherapy followed by targeted radiotherapy. Fortunately, follow-up MRI and PET revealed a complete radiological and metabolic response of the lesion, and he was declared in remission.
Osteolymphoma is also referred to as primary bone lymphoma, and is a rare form of bone cancer. It most commonly manifests as a non-Hodgkin's lymphoma, particularly DLBCL. Fortunately, they tend to respond well to treatment with 5-year survival rates reported as high as 95% with combined chemoradiotherapy 1.
Unable to process the form. Check for errors and try again.