Cutaneous T-Cell Lymphoma (CTCL) can indicate a greater risk for secondary malignancies such as breast, lung, skin, and lymphoma cancers. Mycosis Fungoides (MF) and Sézary Syndrome (SS) are two subgroups of CTCL. The primary measure was to determine if those with MF or SS have an increased risk of developing secondary malignancies and if so, which cancers compared to the general population.


SEER-18 data was sorted using the computer processing language, Julia, to determine the number of secondary cancers developed 5 and 10 years after the original diagnosis of MF or SS. Standardized Incidence Ratios (SIR) were calculated by comparing the secondary cancer incidence with the age-adjusted incidence rates of the general population using NIH data from 2011-2015. Patients diagnosed with MF in 2001 or later were included when determining the frequency of secondary cancer for the 10-year risk. Patients diagnosed in 2006 or later with MF or SS were used to calculate the 5-year cancer risk. The secondary cancers that occurred from 2011-2016 were calculated. Patients who developed MF or SS after being diagnosed with another form of cancer were excluded. Funding was provided by the Brown Center for Biomedical Informatics as well as the National Institutes of Health grants [U54GM115677] and [R25MH116440].


There are 10,156 cases of MF in the SEER-18 data set, of which 1,417 (14%) patients have an associated secondary malignancy. There are 337 cases of SS, 35 (10%) of the patients have a recorded secondary malignancy. There were 7,480 (71%) patients who exclusively developed MF or SS without a secondary malignancy. The most common secondary malignancies were Non-Hodgkin’s Lymphoma (Extranodal), Prostate, Breast, Melanoma, and Non-Hodgkin’s Lymphoma (Nodal).


This study, along with previous literature, verifies the increased risk for secondary hematologic and solid organ malignancies after patients have been diagnosed with MF or SS.