Cooperative Fish and Wildlife Research Units Program: Florida
Education, Research and Technical Assistance for Managing Our Natural Resources

Manes, C., R. R. Carthy, R. M. Herren, D. J. Duffy, J. A. Farrell, A. Page-Karjian, C. Skibicki, F. Dunlap, and I. Capua. 2023. Green turtle Fibropapillomatosis: tumor morphology and growth rate in a rehabilitation setting. Vet. Sci. 2023, 10(7), 421;


Fibropapillomatosis (FP) is a neoplastic disease most often found in green turtles (Chelonia mydas). Symptomatic turtles are burdened with potentially debilitating tumors concentrated externally on the soft tissues, plastron, and eyes, and internally on the lungs, kidneys, and the heart. Clinical signs occur at various levels, ranging from mild disease to severe debilitation. Tumors can both progress and regress in affected turtles, with reports ranging from death due to the disease to complete regression. Despite its official discovery in 1938, tumor growth rates are rarely reported. In addition, FP tumors come in two very different morphologies yet, to our knowledge, there have been no quantified differences in growth rates between tumor types. This distinction has been further strengthened throughout years of FP case reports. FP tumors are often ‘rugose’ in texture, with a polypoid to papillomatous morphology, and may or may not be pedunculated. In other cases, tumors are ‘smooth’ with a skin-like surface texture, and little to no papillose structures. In our study, we assessed growth rate differences between tumor morphologies in a rehabilitation setting. We measured biweekly mean tumor growth over time in juvenile green turtles undergoing rehabilitation at the Whitney Laboratory Sea Turtle Hospital in St Augustine, Florida, and compared growth rates between rugose and smooth tumors. Our results demonstrate that both rugose and smooth tumors follow a similar progression pattern, but rugose tumors grew at significantly faster rates (P<0.05) than smooth ones. We also documented regression across several examined tumors, ranging from -0.19% up to -26% biweekly average negative growth. Our study offers a first ever assessment of differential growth rates between tumor morphologies and an additional diagnostic feature that may lead to more accurate disease outcomes. We suggest that tumor morphological categorization (rugose versus smooth) be documented in future FP hospital and field-based health assessments.