Tumor-to-tumor metastasis is an unusual phenomenon wherein one distinct malignancy is present within the substance of another independent tumor. This event is rare, difficult to detect with imaging, and, due to conflicting terminology in the literature, can be challenging to classify. This article reports the first documented case of tumor-to-tumor metastasis involving prostatic adenocarcinoma and myxoid liposarcoma, reviews the available literature for carcinoma metastatic to sarcoma, and discusses the current situation within the context of the established criteria for the classification of combination tumors.
A 55-year-old man with a history of pulmonary metastatic disease underwent thoracentesis for evaluation of a pleural effusion. The pH of the pleural fluid sample was measured using an ABL835 blood gas analyzer, which yielded a value of 7.37. As part of new instrument validation, the sample was immediately tested using an ABL90 analyzer, which generated a markedly lower value of 6.71 (Table 1). A sample from a second patient demonstrated similarly discrepant results. The answers are below.
ANSWERSInappropriate collection practices resulting in lidocaine HCl contamination have been shown to decrease the reported pH of pleural fluid (1 ). Patient 2's sample was available for follow-up testing using GC-MS, which revealed a lidocaine concentration of 560 g/mL (5.6% contamination with a 10 mg/mL stock solution). Testing of experimental spiked solutions confirmed that both instruments generated decreasing pH results with increasing lidocaine concentration. It is unclear why the ABL90 demonstrated greater susceptibility than the ABL835.
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