Hodgkin Lymphoma



Hodgkin Lymphoma


Todd M. Blodgett, MD

Alex Ryan, MD

Barry McCook, MD









Graphic demonstrates a typical appearance of Hodgkin lymphoma in the anterior mediastinum as a fairly homogeneous mass image, typically with low attenuation on CT.






Coronal PET (A), axial CT (B) and fused PET/CT (C) demonstrate an anterior mediastinal mass image with intense FDG activity, compatible with Hodgkin lymphoma.


TERMINOLOGY


Abbreviations and Synonyms



  • Hodgkin lymphoma (HL)


  • Hodgkin disease (HD)


  • Lymph nodes (LN)


Definitions



  • Malignant neoplasm arising from lymphocytes


  • Rare variety is derived from histiocytes


IMAGING FINDINGS


General Features



  • Best diagnostic clue



    • FDG PET/CT



      • Enlarged FDG-avid lymph nodes/conglomerate mass


      • In usual location: Anterior mediastinum with other nodal groups


    • CT



      • Mediastinal lymphadenopathy presenting as mediastinal mass


      • ± Hepatomegaly, splenomegaly, lung nodules/infiltrates, pleural effusions


  • Location



    • Uncommon spread to extralymphatic locations



      • CNS, spine


    • Usual spread is to contiguous lymph nodes



      • Then to viscera or bone marrow


    • 30-40% of patients present with splenic involvement


    • 5-14% of patients have bone marrow involvement


    • Bone involvement



      • Primary bone invasion does not affect staging; rare (1-4%) at presentation


      • Hematogenous spread indicates stage IV disease


      • Stage IV occurs in 5-20% of patients during disease course


    • 6% of patients have chest wall involvement



      • Requires more aggressive therapy due to higher relapse rate


    • Thymic involvement considered “nodal”



      • Does not count as extranodal disease


      • Not associated with change in disease stage


      • Up to half of patients with thoracic HL may show enlarged thymus



      • Present after successful treatment as a result of rebound thymic hyperplasia


      • Occasionally develop thymic cysts


    • Rare locations



      • Peritoneal and omental involvement found only in non-Hodgkin lymphoma


      • Renal parenchyma is rarely involved, although perirenal space may be invaded


      • GI tract uncommon and usually due to nodal extension


  • Morphology



    • Rounded or bulky soft tissue mass due to nodal aggregation


    • Large masses may have areas of necrosis, hemorrhage, or cyst formation


Imaging Recommendations



  • Best imaging tool



    • PET/CT



      • Best for staging HD (sensitivity 94-98% and specificity 95-100%)


    • MR



      • To delineate soft tissue margins and evaluate spinal cord impingement


  • Protocol advice



    • Baseline FDG PET images should be obtained for initial staging



      • Prior to treatment


    • Patient should be kept warm and avoid activity prior to scan



      • Reduces physiologic uptake in muscle and fat


    • Low dose CT is acceptable for evaluating response to therapy


CT Findings



  • CT has replaced more complicated invasive diagnostic procedures



    • Method of choice for identification of disease invisible on clinical exam


    • Rarely performed anymore: Laparotomy/splenectomy, lymphangiography, and mediastinoscopy


  • Lymphadenopathy



    • Lymph node enlargement and aggregation



      • Appearance of multiple round or bulky soft tissue masses


    • Large masses may develop necrosis, hemorrhage, or cyst formation (10-20%)


    • Minimal contrast enhancement


    • Calcification rare before treatment but 20% prevalence post-radiotherapy



      • Rim calcification


      • Multiple discrete deposits (mulberry)


    • CT useful for treatment/radiation planning


  • Extralymphatic involvement



    • Mediastinal structures may show displacement, compression, or invasion


    • Cortical bone well evaluated with CT


    • Poor sensitivity for bone marrow disease


    • Invasion of gallbladder and pancreas usually from adjacent nodal disease



      • Absence of pancreatic capsule hinders diagnosis of invasion vs. contact


    • Thymic mass may be discrete or infiltrating


  • Therapy response



    • Tumor masses have low density of malignant cells


    • Reduction in volume of lesion is an insensitive predictor of response


Nuclear Medicine Findings



  • Initial diagnosis



    • Involved lymphoid tissue generally shows increased FDG uptake



      • No differentiation of subtypes by SUV has been demonstrated


    • Focal, super-physiologic uptake in nodal or extranodal tissue fairly specific indicator of disease



      • Diffuse uptake more difficult to interpret


      • Awareness of common FDG PET false positives is essential


    • Uptake may be seen in spleen and liver



      • Focal increased FDG activity generally indicative of malignant involvement


  • Staging




    • For organ staging, PET/CT seems to have no obvious advantage over FDG PET alone



      • Except in reducing false positives by better characterization of lesions using CT


    • Pooled true positive rate of FDG PET for HL: 90%



      • Upstaging rate: 8-25%


      • Shift to more advanced treatment: 10%


      • Downstaging: 2-23% (mean less than for upstaging)


      • FDG PET inclusion criteria are more accurate than CT inclusion criteria


      • Size is an insensitive indicator of malignancy


      • Enhancement characteristics are unreliable for inclusion


      • Combined PET/CT is superior for lesion delineation in radiotherapy planning


    • Bone marrow involvement



      • Diffuse marrow involvement may be intense


      • May also be indistinguishable from background


      • May be misinterpreted as negative for disease with diffuse marrow activity


      • Increased uptake can be iatrogenic


      • G-CSF, erythropoietin


      • Beta-thalassemia also increases uptake


      • Bone marrow biopsy (BMB) and PET/CT are complementary


      • Similar sensitivity/specificity but discordant findings


      • BMB more sensitive for detection of diffuse disease


      • PET/CT more likely to detect patchy disease


    • Spleen and liver



      • Full dose diagnostic CT necessary for adequate evaluation of liver and spleen


      • Splenic involvement may appear as diffusely increased uptake


      • Also seen in “reactive” spleen


      • Liver involvement may appear as diffuse uptake or patchy uptake in portal areas


      • Less commonly as large focal lesions


    • Response to therapy


    • SUV reduction of 60% is used as cutoff to separate treatment responders from nonresponders


    • PET has prognostic value after chemotherapy: 5 year survival after 2-3 cycles of chemo



      • 92% for PET-negative group


      • 39% for PET-positive group


    • 2 year progression-free survival after 2 cycles of ABVD-like chemo



      • 94% for PET-negative patients


      • 0-6% for early PET-positive patients


    • Study showed no evidence that patients benefit from treatment alteration based on early PET



      • Patients with PET-negative residual mass after chemo who received radiotherapy to original bulky site had 2.5% relapse rate within 18 months vs. 14% relapse in non-radiotherapy arm


      • In contrast, the International Prognostic Index (IPS) poorly predicts improved survival


DIFFERENTIAL DIAGNOSIS


Granulomatous Process



  • Active disease positive on FDG PET


  • Infectious and non-infectious etiologies


  • Will usually resolve over time


  • More likely bilateral hilar and paratracheal distribution


Infections



  • Pyogenic, fungal, parasitic, HIV-related, viral (e.g., varicella, zoster, HCV, CMV)


  • Usually positive on FDG PET


Other Malignancy



  • Variable enhancement and FDG uptake


  • History is crucial


Normal Lymphoid Tissue



  • Physiologic uptake common in Waldeyer ring, thymic tissue, cervical nodes


  • Asymmetric uptake can occur normally and may be mistaken for malignancy


Reactive Lymph Nodes



  • Usually much smaller than typical aggressive Hodgkin


PATHOLOGY


General Features



  • Genetics



    • 1% of patients with HD have family history of disease


    • Sibling of affected individual has 3-7x increased risk



      • Higher in monozygotic twins


    • HLA-DP alleles more common in HD


  • Etiology



    • Unknown


    • Infection may be involved in pathogenesis, particularly Epstein-Barr virus (EBV)



      • Tumor cells are EBV-positive in ˜ 50% of HD cases


      • Positivity higher in MCHD (60-70%) than in NSHD (15-30%)


      • ˜ 100% of HIV-related HD are EBV-positive (though HD is not an AIDS-defining condition)


  • Epidemiology



    • 8,000 new cases and 1,000 deaths occur in the USA annually


    • Incidence: 3-4/100,000 per year


Gross Pathologic & Surgical Features



  • Cut surface white-gray and uniform


  • Affected LN



    • Usually enlarged


    • Shape is preserved


    • Capsule is not invaded


    • Surface may be nodular in nodular sclerosis subtype


Microscopic Features



  • Prominent lymphocytic infiltrate and Reed-Sternberg cells



    • Reed-Sternberg cells: Large, binucleate, with characteristic CD15+, CD30+ immunophenotype


  • Core biopsy preferred over fine needle aspiration




    • Malignant cells in HL make up only a very small, scattered proportion of the tumor volume


    • Subtyping requires core biopsy


    • Tumors pleomorphic


  • Bone marrow disease is often patchy and focal resulting in low sensitivity of bone marrow biopsy



    • If positive on PET, directed biopsy of that area increases true positive yield

Sep 22, 2016 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Hodgkin Lymphoma
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