Difficult Diagnostic and Therapeutic Cases

[Rebound (reactive) thymic hyperplasia after chemotherapy in children with lymphoma]

INTRODUCTION

Thymic regrowth after chemotherapy treatment has been reported in children with lymphoma, and in order to avoid misdiagnosing these cases as relapses, physicians should become familiar with rebound (reactive) thymic hyperplasia (RTH) and remain aware of its possible occurrence. We aimed to estimate the prevalence of RTH in children with lymphoma after completion of chemotherapy and to evaluate the clinical characteristics, outcomes, and the findings of computed tomography (CT) and gallium-67 (GA-67) scans in these patients.

PATIENTS AND METHODS

We conducted a retrospective cross-sectional study by reviewing the health records of children with a lymphoma diagnosis managed at an outpatient paediatric oncology clinic in Jeddah, Saudi Arabia.

RESULTS

Rebound thymic hyperplasia was detected in 51.9% of the lymphoma patients (14/27). It developed a median of 2.5 months after completion of chemotherapy (range, 2.0-4.25 months). Patients with RTH had significantly shorter treatment durations, and we found no significant differences between patients with and without RTH in sex, age at diagnosis, type of lymphoma or type of treatment received. All patients with RTH were asymptomatic, and routine laboratory tests did not detect any abnormalities in them. The findings of CT and GA-67 scans were highly suggestive of RTH. None of the patients with RTH had a recurrence, and RTH resolved spontaneously within a median of 6 months (range, 4.0-11.0).

CONCLUSION

RTH was detected in ∼50% of children with lymphoma after completion of chemotherapy. A clinical evaluation and laboratory tests combined with imaging by CT and GA-67 can help identify RTH and rule out other lesions elsewhere.

Prevention and treatment of tumor lysis syndrome, and the efficacy and role of rasburicase

Tumor lysis syndrome (TLS) is a potentially life-threatening condition that occurs in oncologic and hematologic patients with large tumor burden, either due to cytotoxic therapy or, less commonly, spontaneously because of massive tumor cell lysis. TLS is clinically characterized by acute renal failure, hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia. While limited options are available for treating TLS, identifying patients at high risk for developing TLS and prevention in high-risk patients remain an important aspect in the treatment of cancer patients. In general, treatment of TLS consists of intensive hydration, stimulation of diuresis, and, more specifically, in the use of allopurinol and rasburicase. Rasburicase, a recombinant urate oxidase, rapidly and effectively reduces hyperuricemia, which subsequently significantly decreases the risk of acute renal failure and other clinical manifestations of TLS. For this review, a comprehensive literature search using the term “tumor lysis syndrome” and/or “rasburicase” was performed considering articles listed in MEDLINE. Incidence, prevention, and therapy of TLS with a special focus on the role of rasburicase are discussed. We evaluated 120 relevant articles including 35 case reports, 32 clinical trials, and 14 meta-analyses.

Clinical analysis of thymic regrowth following chemotherapy in children and adolescents with malignant lymphoma

OBJECTIVES

Thymic regrowth following chemotherapy has typical clinical and imaging manifestations that can be used to diagnose it prior to pathological diagnosis. We investigated methods for diagnosing thymic regrowth following chemotherapy with non-invasive methods.

METHODS

Our study included 26 children and adolescents with thymic regrowth following chemotherapy for malignant lymphoma. Computed tomography scans were routinely performed for follow-up observations. After the emergence of new mediastinal masses, patients either underwent Fluorine-18 fluorodeoxyglucose-positron emission tomography scans to identify the characteristics of the mass, or were closely followed up.

RESULTS

Thymic regrowth occurred 1-12 months after the last chemotherapy (mean, 4 months). Computed tomography mostly revealed diffusely enlarged thymic parenchymatous tissues that maintained normal thymic morphology. Computed tomography values were 36.72 ± 9.48 Hu and increased by 5.56 ± 2.62 Hu in contrast enhancement. The mean volume of the mass was 19.2 cm(3). Twenty patients underwent positron emission tomography; among them, five (25%) showed no intake of Fluorine-18 fluorodeoxyglucose in the anterior mediastinal mass, and 15 (75%) showed radioactivity distribution in the mass with a mean standardized uptake value of 2.7; the shape was regular and radioactivity distribution was uniform. The mean follow-up duration was 40 months and all patients achieved disease-free survival.

CONCLUSIONS

In the absence of pathological diagnosis, thymic regrowth following chemotherapy can be diagnosed by clinical features combined with characteristic manifestations in computed tomography and positron emission tomography scans.

Ectopic thymic hyperplasia in a patient treated for Burkitt lymphoma

Thymic hyperplasia results from thymic regrowth after atrophy during stressful conditions such as burns, surgery, infection, and chemotherapy. Although thymic lesions are relatively common causes of anterior mediastinal masses, they also can develop in other mediastinal compartments on rare occasions. It is well known that thymic tissue can develop in ectopic intrathoracic lesions. Few cases of ectopic thymus associated with disturbance during thymus embryogenesis have been reported as incidental findings. We report the case of a 4-year-old boy with true thymic hyperplasia from an ectopic thymus after successful treatment for Burkitt lymphoma. This is a rare finding in the differential diagnosis of a middle mediastinal mass in a child following chemotherapy for lymphoma. The diagnosis of thymic hyperplasia from an ectopic thymus can be confirmed only histologically.

[Thymic hyperplasia following treatment for nephroblastoma]

Thymic hyperplasia in response to stress is a well known phenomenon. Thymic hyperplasia has also been described after chemotherapeutic treatment for malignancies in children.

CASE REPORT

A three-year-old girl was followed up from the age of 18 months for a left kidney nephroblastoma treated by combination of chemotherapy (vincristin, actinomycin and adriamycin) and surgery. Assessment at the end of treatment was normal. Four months after the end of treatment, pulmonary radiography showed mediastinal enlargement, which was shown to originate in the thymus at thoracic CT scan. A recurrence of the disease was suspected. Biopsy showed thymic hyperplasia without evidence of tumor cells. Mediastinal enlargement then disappeared spontaneously 2 months later.

CONCLUSION

Thymic hyperplasia occurring during remission of a cancer treated by chemotherapy is a diagnostic dilemma as it suggests mediastinal reccurence of the disease. Needle aspiration cytology is an appropriate investigation in thymic hyperplasia. No steroid therapy should be used before histologic diagnosis of thymic hyperplasia.

Infective Mesenteric Adenitis Masquerading as Relapsed Non-Hodgkin's Lymphoma

Bulky mesenteric lymphadenopathy and B symptoms in a patient with a prior history of relapsed histologically aggressive non-Hodgkin's lymphoma would usually be attributed to recurrent disease. In the case described here, recurrent lymphadenopathy was found to be due to probable Yersinia infection, highlighting the need for rebiopsy of tissue in these circumstances wherever possible.