A Review of Non-Invasive Skin Imaging in Merkel Cell Carcinoma: Diagnostic Utility and Clinical Implications

Abstract

Background/Objectives: Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous neuroendocrine malignancy characterized by its propensity for rapid growth and early regional and distant metastasis. Given its potentially lethal nature, accurate and timely diagnosis of MCC is of utmost importance. This review aims to describe non-invasive imaging methods that can serve as additional tools in the examination of MCC. Methods: In this narrative review, we describe the up-to-date spectrum of non-invasive skin-imaging methods that can serve as additional tools in the examination of MCC based on the available literature. Dermoscopy might enhance the clinical diagnosis of MCC, facilitate differentiation from other benign and malignant tumors, and help optimize the treatment plan. New imaging technologies might also provide useful information at a sub-macroscopic level and support clinical diagnosis. These techniques include high-frequency ultrasound (HFUS), reflectance confocal microscopy (RCM) and optical coherence tomography (OCT). Results: Clinically, MCC typically presents as a rapidly growing, red, purple or skin-colored painless and firm nodule. Diagnosis is usually established with histopathological assessment and immunohistochemistry. However, dermoscopy and new imaging technologies might enhance the clinical diagnosis of MCC, facilitate differentiation from other benign and malignant tumors, and help optimize the treatment plan.

Keywords: Merkel cell carcinoma; dermoscopy; high-frequency ultrasound; non-invasive; nonmelanoma skin cancer; reflectance confocal microscopy; skin imaging.

Figure 1

A nodular pink lesion located on the forearm. Courtesy of Prof. Caterina Longo.

Figure 2

A partially ulcerated pink nodule on the back of a 78-year-old man. Courtesy of Prof. Caterina Longo.

Figure 3

Dermoscopy shows an asymmetric pattern with ulceration, polymorphous vessels, pinkish to cherry-red color, and shiny white structures. Courtesy of Prof. Caterina Longo.

Figure 4

Dermoscopy shows polymorphous vascular patterns, milky red areas on a white background, and arborescent large-caliber vessels. Courtesy of Prof. Ana-Maria Forses.

Figure 5

RCM shows the presence of aggregates of small monomorphic cells surrounded by fibrotic septae. Courtesy of Prof. Caterina Longo.

Figure 6

RCM shows small hyporeflective cells arranged to form solid aggregates surrounded by non-reflective stroma. Courtesy of Prof. Caterina Longo.