Thymoma: Benign Appearance, Malignant Potential

Abstract

Thymoma is a rare tumor with a largely indolent growth pattern. It does, however, have malignant potential as a result of its ability to invade locally and metastasize regionally. Often associated with a number of immuneand nonimmune-mediated paraneoplastic syndromes, patient outcomes are directly related to stage of disease and the ability to achieve a complete surgical resection. Surgery is the mainstay of treatment, with adjuvant radiation recommended for invasive thymoma. Sensitive to both chemotherapy and radiation, durable responses are achievable in incompletely resected and inoperable patients. We present two cases of thymoma followed by a general discussion with an emphasis on treatment for both early and advanced-stage disease. The Oncologist 2006;11:887-894 Case Presentation 1A 62-year-old woman, with no significant past medical history, presented to her primary care physician in November of 2005 for a routine physical exam. A chest x-ray was performed, in the absence of symptoms, which surprisingly revealed a right paramediastinal mass. Computed tomography (CT) scan of the chest revealed a 5.3-× 3.0-cm mass in the anterior mediastinum ( Fig. 1) with hypermetabolic activity by positron emission tomography (PET) scan. Fineneedle aspiration (FNA) performed at an outside hospital revealed a spindle-cell neoplasm consistent with thymoma. Routine laboratory studies were unrevealing, with the exception of quantitative immunoglobulins, which revealed decreased levels of IgA (68 mg/dl; normal range, 81-463), IgG (393 mg/dl; normal range, 694-1,618), and IgM (<5 mg/dl; normal range, 48-270). The patient was referred to the thoracic oncology program at our institution for evaluation and treatment. Case Presentation 2A 45-year-old Caucasian woman, with no significant past medical history, presented to an outside tertiary care facility in June of 2001 with complaints of slurred speech, difficulty swallowing, and blurry vision, and was diagnosed with myasthenia gravis. As part of the evaluation, imaging of the chest was performed, revealing a 10-cm right costophrenic mass with associated pleural-based lesions. The patient was referred to a thoracic surgeon who performed a thoracoscopic biopsy of a pleural-based mass, revealing lymphocyte-rich thymoma. She was deemed inoperable and received six cycles of cisplatin, doxorubicin, and cyclophosphamide (PAC) chemotherapy followed by radiation therapy. She had a durable response for 4.5 years and was followed with serial CT scans every 6 months. The most recent CT scan performed in December of 2005 revealed a right anterolateral pleural-based lesion (Fig. 2), which had increased in size from prior examination and was hypermetabolic by PET scan. An FNA was performed, revealing recurrent thymoma. The patient was referred to the thoracic oncology program at our institution for evaluation and treatment.

The Incidence of Myasthenia Gravis: A Systematic Literature Review

“…Anti-muscle-specific tyrosine kinase antibody testing is also used in diagnosing seronegative myasthenia gravis [10] . Around 75% of the patients with myasthenia gravis exhibit thymic abnormalities, and it has been suggested that the pathogenesis of the disease starts in the thymus: 60-70% have thymic hyperplasia and 10-15% have a thymoma [1,3,4,11] .…”

Protein expression status of p53 and epidermal growth factor receptor in thymoma

“…For example, our present study showed that only clinical stage is an independent prognostic factor, as compared to pathological classification and completed resection. In addition, although thymoma is basically indolent in its early stage, certain investigators asssert that occasionally benign-appearing thymoma is potentially malignant (25,26). Furthermore, clinical doctors have not achieved a standardized solution to classify thymoma into typical TMN classifications.…”

Immunological disturbances in Good’s syndrome

“…CT allows for the characterization of tumour and describes possible invasion into surrounding structures. 6 High-resolution CT is helpful for the detection of pulmonary abnormalities, especially fast progressive bronchiectasies which are very frequent in Good's syndrome patients. 7 Such a picture was present in our patient.…”