Ultrasound, Dermoscopy May Alleviate Need to Biopsy the Nail
FLORENCE, ITALY — High-resolution ultrasound and dermoscopy hold promise for distinguishing straightforward benign nail conditions from suspicious lesions that require a biopsy, researchers said at the 13th Congress of the European Academy of Dermatology and Venereology.
High-frequency ultrasound is valuable because it clearly visualizes landmarks of the normal nail, said Gregor Jemec, M.D., of Roskilde Hospital in Copenhagen. The technique reveals the bilamellar structure of the nail plate with a well-hydrated deep layer, the matrix, a clear subungual space, and bone. These structures are preserved with ultrasound even when the patient is wearing acrylic nails or when there are traumatically induced waves across the nail plate.
The higher the frequency of the ultrasound, the more detailed the image. The lowest frequency useful for imaging nails is 15 MHz, while a 28-MHz transducer provides strikingly detailed images of nail structure, Dr. Jemec said.
In discussing patients with psoriasis, Dr. Jemec said the distal portion of the nail may reflect disruption of the nail plate and a hypoechogenic region, although the matrix is unaffected. By measuring the distance between the nail plate and underlying bone, ultrasound may provide a way to quantify the thickness of psoriatic plaques, either for research purposes or to gauge the effectiveness of therapy, Dr. Jemec said.
He noted that using ultrasound with Doppler enables subungual tumors to be visualized. For example, abnormal blood flow can point to glomus tumors.
Dermoscopy is very useful for determining which pigmented nail conditions warrant a biopsy, explained Luc Thomas, M.D., professor of dermatology at the Hospital de l'Hotel-Dieu in Lyon, France.
He suggested using an antiseptic gel or ultrasound gel to enhance the resolution of dermoscopic images.
In studying dermoscopic images of 148 pigmented nails and comparing them with results from biopsies, Dr. Thomas and his associates noted a number of patterns that provided important diagnostic clues:
▸ Blood spots. Blue-purple following a recent injury and brownish-black later in the healing process, these round spots at the proximal edge of the nail, as well as filamentous patterns at the end of the nail, strongly suggest subungual hemorrhages rather than melanocytic pigmentation. However, they do not rule out melanoma.
▸ Brown longitudinal parallel lines. These structures are key to distinguishing suspicious lesions that should be biopsied. Are the lines irregular in color, spacing, or thickness? Is the parallel pattern of the lines disrupted?
▸ Brown or black background coloration. This finding suggests melanistic hyperplasia, due to nevi or melanoma.
▸ A homogeneous gray background. This finding does not suggest melanocytic hyperplasia but rather other diseases or characteristics, including ungual lentigo, ethnic pigmentation, or drug- or trauma-induced hyperpigmentation.
▸ Micro-Hutchinson's sign. This rare finding, defined as the absence, or very faint pigmentation, of the cuticle, was seen only in patients with melanoma.
