Green Turtle Fibropapillomatosis: Tumor Morphology and Growth Rate in a Rehabilitation Setting

Fibropapillomatosis (FP) is a neoplastic disease most often found in green turtles (Chelonia
mydas). Afflicted 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 outcomes ranging from death due to the disease to complete
regression. Since its official description in the scientific literature in 1938, tumor growth rates have
been rarely documented. 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.
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 rugose
and smooth tumor morphologies in a rehabilitation setting. We measured average biweekly tumor
growth over time in green turtles undergoing rehabilitation at the University of Florida Whitney
Laboratory Sea Turtle Hospital in St. Augustine, Florida, and compared growth between rugose and smooth tumors. Our results demonstrate that both rugose and smooth tumors follow a similar
active growth progression pattern, but rugose tumors grew at significantly faster rates (p = 0.013)
than smooth ones. We also documented regression across several examined tumors, ranging from
􀀀0.19% up to 􀀀10.8% average biweekly negative growth. Our study offers a first-ever assessment of
differential growth between tumor morphologies and an additional diagnostic feature that may lead
to a more comprehensive understanding and treatment of the disease. We support the importance of
tumor morphological categorization (rugose versus smooth) being documented in future FP hospital and
field-based health assessments.