Characteristics of Sarcoidosis in Patients with Previous Malignancy: Causality or Coincidence?

Background: The association between sarcoidosis and malignancy is poorly defined. Sarcoidosis can precede, be diagnosed concurrently with, or follow malignancy. Objectives: We describe the clinical and radiological features of patients with sarcoidosis following malignancy to determine whether this association is causal or coincidental. Methods: We performed a search for all patients with confirmed sarcoidosis following malignancy in our institution during 2001-2015. Clinical and radiological features, bronchoscopic findings, bronchoalveolar lavage cell counts, and pulmonary function tests (PFTs) were reviewed to evaluate patterns of disease involvement. Details of the histological type of cancer, staging, treatment, and follow-up were reviewed. Results: Twenty-nine patients were identified. The most prevalent malignancies were breast cancer and lymphoma (24% each). Based on the incidence of these malignancies, we estimated the incidence of sarcoidosis was 175 times higher after lymphoma and 38 times higher after breast cancer as compared to the general population. Most patients had early stage cancer (stage I, II) (75%), and only 2 patients (7%) had recurrence of their malignancy after diagnosis of sarcoidosis. Sarcoidosis was diagnosed within 5 years of malignancy in over half the patients, 76% were asymptomatic and 69% had normal PFTs. Mediastinal lymphadenopathy was present in 81% of cases, hilar lymphadenopathy in 67%, and pulmonary parenchymal involvement in 41%. Fifty percent of patients had received Adriamycin, 38% cyclophosphamide, and 33% vincristine. Conclusions: Sarcoidosis following malignancy is indistinguishable from "idiopathic" sarcoidosis, although it is frequently asymptomatic. The high frequency of sarcoidosis after specific cancers but not others, suggests a causative association between malignancy and development of sarcoidosis.