Malignant thymoma associated with myasthenia gravis, and evidence of extrathoracic metastases.An analysis of published cases and report of a case

Abstract

A case of malignant thymoma with extrathoracic metastases is described and discussed. A review of the literature revealed only 11 such cases previously reported. Pertinent clinical and pathologic data are reviewed and discussed. The age range was 32 to 74 years, with a mean of 49.5 years. The duration of life from onset of symptoms to time of death ranged from 2 1/2 months to 14 years, with a mean of 3.9 years. The relatively rapid evolution from onset of symptoms to time of death was probably related to late diagnosis rather than to aggressiveness of the neoplasm, since this type of tumor is usually slow growing. At postmortem examination, all cases showed a large mediastinal tumor in addition to extrathoracic metastases. Microscopic examination of the tumors found 8 to be predominently epithelial, one made up of spindle cells, 2 of a combination of epithelial and spindle cells, and one of lymphocytic type. The rare occurrence of extrathoracic spread of thymoma is attributed to relative lack of host defenses, though in our reported case a strong desmoplastic reaction is held accountable for the longest reported survival (14 years).

Extrathoracic metastases of thymic origin: a review of 35 cases

“…1,2,[4][5][6]9,[25][26][27][28] The differential diagnosis of the metastatic thymic tumor varies with the site of metastasis. Metastases from a type A thymoma can be confused with spindle cell carcinomas or mesenchymal tumors like hemangiopericytoma.…”

“…In any event, these studies suggest liver, bone, and lymph nodes as common sites of extrathoracic metastases of malignant thymoma. [4][5][6] Moreover, …”

“…2 It is the most aggressive variant invading surrounding structures with metastases, 2 although embolic metastases of thymic carcinoma leading to extrathoracic metastases are very rare. 4 Since, thymic cancers invade locally, diagnoses of metastases are difficult. Locally advanced thymic tumors often present as pleural plaques, which can be misdiagnosed as lung metastases on imaging studies.…”

“…In any event, these studies suggest liver, bone, and lymph nodes as common sites of extrathoracic metastases of malignant thymoma. [4][5][6] Moreover, renal and splanchnic metastases as well as cerebral metastasis, although quite rare, have also been reported. 5 In older literature, a majority of thymomas with metastases were described as epithelial type without any further categorization.…”

WHO types A and AB thymomas: not always benign

“…In majority of cases, relapses have been intrathoracic, although distant sites of progression include the lung, brain, liver, and thoracic spine. 22,29,36 Importantly, in most of these studies, complete excision of the tumor was reported. Interestingly, in the study by Rieker et al, 37 the 43 patients with type A tumors had a worse outcome when compared with patients with AB (n ¼ 20) and B1 (n ¼ 24) tumors.…”