Staging and Diagnostic Evaluation
Staging and evaluation of disease status is undertaken at diagnosis and performed again early in the course of chemotherapy and at the end of chemotherapy.
Pretreatment Staging
Stage is a critical determinant in the selection of treatment. Initial evaluation of the child with Hodgkin lymphoma includes history, physical examination, anatomic imaging (including chest x-ray; computed tomographic [CT] scan of chest, abdomen, and pelvis; functional imaging including positron emission tomography [PET] scan),[1,2,3] and laboratory studies. The posteroanterior and lateral chest radiograph remains important since the criterion for bulky mediastinal lymphadenopathy is defined by the ratio of the measurement of the mediastinal lymph nodes to the maximal measurement of the chest cavity on an upright chest radiograph; mediastinal ratios 33% or higher are considered bulky. CT scans help delineate the status of intrathoracic lymph node groups (including the hila and cardiophrenic angle), lung parenchyma, pericardium, pleura, and the chest wall, demonstrating abnormalities in about one-half of patients with unremarkable chest radiographs. Definition of disease involvement of intrathoracic tissues by CT will often dictate more aggressive therapy than would otherwise have been administered. Distinguishing normal (or hyperplastic) thymus from nodes in children can be problematic. Bone marrow biopsy should be performed in patients with advanced disease (stage III or stage IV) and/or symptoms (fever, weight loss, or night sweats).[4] PET scans are reliable in assessing bone involvement. Stage is determined by anatomic evidence of disease by CT scanning in conjunction with functional imaging. A suspected anatomic lesion which is PET-negative should not be considered involved unless biopsy-proven. Areas of PET positivity, which do not correspond to an anatomic lesion, (by clinical examination or CT scan) should be disregarded in staging. Functional imaging (fluorodeoxyglucose [FDG]-PET scan) is sensitive in determining initial sites of involvement, particularly in the neck and mediastinum. PET scanning may be particularly useful in demonstrating unsuspected areas of involvement in the spleen and bone. FDG-PET has advantages over gallium-67 because the scan is a 1-day procedure with higher resolution, better dosimetry, and less intestinal activity.[1] FDG-PET is now the recommended functional imaging procedure for initial staging.[5,6]
Patients with large mediastinal masses are at risk of cardiac or respiratory arrest during general anesthesia or heavy sedation.[7,8,9,10] Although this is less likely to be problematic in Hodgkin lymphoma than in non-Hodgkin lymphoma, appropriate planning of the surgical approach is essential. After a careful physiologic and radiographic evaluation of the patient has been carried out, the least invasive procedure should be used to establish the diagnosis of lymphoma. If at all possible, the diagnosis should be established by lymph node biopsy. Aspiration cytology alone is not recommended because of the lack of stromal tissue, the small number of cells present in the specimen, and the difficulty of classifying Hodgkin lymphoma into one of the subtypes. In cases where general anesthesia may pose a risk, a CT or ultrasound-guided core needle biopsy should be considered. This procedure can frequently be carried out using light sedation and local anesthesia. Mediastinoscopy, anterior mediastinotomy, or thoracoscopy are the procedures of choice when other diagnostic modalities fail to establish the diagnosis. A formal thoracotomy is rarely indicated for the diagnosis of Hodgkin lymphoma. If a diagnostic operative procedure cannot be performed because of the risk of general anesthesia or heavy sedation and if needle biopsy is not feasible, then preoperative treatment with localized radiation therapy should be considered. Because preoperative treatment may hinder an accurate tissue diagnosis, a diagnostic biopsy should be obtained as soon as the risks of general anesthesia or heavy sedation are thought to be alleviated.
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