Add Points for Mycosis Fungoides Dx

WAIKOLOA, HAWAII — The standardized, points-based diagnostic algorithm for early mycosis fungoides developed by the International Society for Cutaneous Lymphoma can be helpful in approaching the ambiguous patient with a patchy, thin-plaque rash and some atypia in the biopsy, Dr. Kimberly Bohjanen said at the annual Hawaii dermatology seminar sponsored by Skin Disease Education Foundation.

In the past, such a patient might visit four different physicians and variously receive a diagnosis of parapsoriasis, atopic dermatitis, contact dermatitis, or early classic cutaneous T-cell lymphoma (CTCL), noted Dr. Bohjanen of the University of Minnesota, Minneapolis.

Although the algorithm—codeveloped by the Cutaneous Lymphoma Task Force of the European Organisation for Research and Treatment of Cancer—might seem confusing at first, it really is not. In fact, it's akin to the scoring system rheumatologists developed to define systemic lupus, she said.

Four points are required to diagnose early mycosis fungoides. Up to two can come from the clinical exam. The basic clinical criterion is the presence of persistent and/or progressive patches and thin plaques. The additional clinical criteria are a non-sun-exposed "bathing suit"-type lesion distribution, poikiloderma, and variation in lesion size and shape. A patient gets one point for presenting with the basic clinical criterion plus one of the additional criteria, or two points for presenting with the basic criterion plus any two additional clinical criteria.

Up to two points can be awarded based on the histopathologic findings on biopsy.

The basic histopathologic criterion is the presence of a superficial lymphoid infiltrate. If this, plus either of the two additional criteria—epidermotropism without spongiosis, and lymphoid atypia as defined by enlarged, irregular, hyperchromatic nuclei—are met, that's worth one point. If the basic and both additional criteria are present, that's worth two points.

"So basically if you have someone with a classic presentation of CTCL that meets the criteria on clinical exam and then you have a biopsy with all of these features, you've made the diagnosis of CTCL without even going on to immunotyping or T-cell gene rearrangement," she said.

All of this presupposes that the possibility of drug eruption has been ruled out from the outset.

A subsequent biopsy is used to gather material for T-cell gene rearrangement and immunopathologic studies. These studies need to be done routinely because of their value in staging, even in patients who already have four points.

One additional point is awarded for evidence of clonality on T-cell gene rearrangement. The algorithm gives another point if at least one of the following three immunopathologic markers of CTCL is present on the cell surface: less than 50% CD2-positive, CD3-positive, or CD5-positive T cells; less than 10% CD7-positive T cells; and discordance between the epidermal and dermal population of CD2, CD3, CD5, or CD7 T cells, with the antigen deficiency being confined to the epidermis (J. Am. Acad. Dermatol. 2005;53:1053–63).

The new system follows the T (tumor), N (lymph nodes), M (visceral metastases), and B (blood—with or without circulating Sézary cells) format (Blood 2007;110:1713–22). The biggest change was in lymph node staging, which now incorporates clonality, she said.

Dr. Bohjanen disclosed being on the speakers bureau for Abbott Laboratories.

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