Introduction. Sarcoidosis is a granulomatous disease that mostly involves the lungs. Its association with malignancies has been well documented. Several mechanisms have been proposed that may underlie this concurrence including triggering tumour antigens and defective cellular immunity. Case presentations. We briefly review the literature on malignancy associated sarcoidosis and report two female lymphoma patients of 49 and 56 years of age who, during their course of disease, developed sarcoidosis that was misinterpreted as a lymphoma relapse on positron emission tomography-computed tomography. Conclusion. We hypothesise that T cell dysfunction and exposure to tumour associated antigens might be the underlying mechanisms of development of sarcoidosis in patients with lymphoma. Positron emission tomography-positive lesions do not always indicate malignancy and therefore a tissue biopsy is always mandatory to confirm the diagnosis. © 2009 licensee BioMed Central Ltd.