Protein Can Help Identify Which Rashes Are Early Mycosis Fungoides

John Zic, MD, dermatologist, Tennessee Valley VAMC,
professor, Vanderbilt University School of Medicine

Chronic rash in a sun-protected area that doesn’t respond to topical treatment likely needs to be evaluated for mycosis fungoides, the most common variant of cutaneous T-cell lymphoma. Now, a new VA study reports that a protein expression can help make the diagnosis.

By Annette M. Boyle

NASHVILLE, TN—In its early stages, mycosis fungoides can easily be mistaken for a number of other skin conditions such as eczema and psoriasis. The most common variant of cutaneous t-cell lymphoma (CTCL) has one tell-tale sign that can help physicians identify it much more reliably—and years sooner.

“Mycosis fungoides often take six to 10 years to diagnose, not because healthcare providers are missing the diagnosis, but because it takes time for enough changes to take place in the skin for the malignancy to be detected by a pathologist,” explained John Zic, MD, a dermatologist at the Tennessee Valley VAMC and professor at the Vanderbilt University School of Medicine.

In its early stages, mycosis fungoides can easily be mistaken for a number of other skin conditions such as eczema and psoriasis.

Indolent malignancy occurs most often in older males, “so we would expect there to be a higher percentage of veterans with mycosis fungoides and CTCL than in the general population,” Zic noted.

In an article published in the Journal of the European Academy of Dermatology and Venereology, Zic and his Vanderbilt colleagues, led by Laura McGirt, MD, confirmed that mycosis fungoides (MF) increases expression of thymocyte selection-associated HMG box protein (TOX). In addition, they found that large plaque parapsoriasis (LPP) also increases TOX expression. While LPP is not considered a malignancy itself, 10-20% of people who have it will go on to develop MF. 1

The team stained and analyzed samples with MF (53), other forms of cutaneous t-cell lymphoma (20), large plaque parapsoriasis (10), normal skin (2) and benign inflammatory dermatoses (17). Of the 53 MF samples, 73.6% stained positively and 62.3% showed strong positive results. The benign conditions, in contrast, picked up any TOX expression in 31.6% of samples and only one (5.3%) was strongly positive.

“If there is a strong expression of the TOX marker with staining on skin biopsies, then the positive predictive value for MF is almost 97%,” Zic told U.S. Medicine. “That’s significant because many skin disease have lots of t-cell lymphocytes in the skin. This helps us distinguish which ones are likely MF, an early lymphoma of the skin, and which are benign.” TOX has a negative predictive value of 47%, he added.

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