Surender,

Here's a quote I found: •Serpentine hyperpigmentation: Some chemotherapy drugs (fluorouracil, vinorelbine, and some combination regimens) given intravenously (IV) can cause a darkening of the venous pathways up the arm. This darkening over the veins will eventually fade. ◦The cause of these skin reactions is currently unknown, but may involve direct toxicity, stimulation of melanocytes (cells in skin responsible for skin color), and postinflammatory changes. Although skin reactions may occasionally be permanent,in most cases, discoloration will gradually resolve after chemotherapy is stopped.

Thanks Lee Henderson for sharing a valuable information.

This Serpentine hyperpigmentation is also not there in the CTCAE Dictionary. I'm trying to grade these events according to CTCAE dictionary, but I'm not getting exact/related term.

Skin hyperpigmentation is on Page 147 of Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0 Published: November 27, 2017 (accessed 19.3.19 from https://ctep.cancer.gov/protocolDevelopment/electronic_applications/docs/CTCAE_v5_Quick_Reference_5x7.pdf#search=%22hyperpigmentation%22). You would need to code it as < or > 10% surface area and whether there was any psychosocial impact.

Thanks Peter Alexander for your valuable suggestions.