[493] T-Cell Receptor PCR from Separate Biopsies Distinguishes Granulomatous Dermatitis from Granulomatous Mycosis Fungoides

S Dabiri, DA Arber, YH Kim, UN Sundram, J Kim. Stanford University Medical Center, Stanford, CA

Background: The presence of a granulomatous tissue reaction in association with cutaneous T-cell lymphoma (CTCL), in particular mycosis fungoides (MF), is rare but well-documented. The diagnosis of MF may be difficult in cases where an exuberant granulomatous inflammatory infiltrate obscures the neoplastic lymphoid infiltrate, mimicking a granulomatous dermatitis. In these cases, the clinical evolution of the disease process, coupled with the demonstration of a monoclonal lymphoid T-cell population, may assist in establishing a definitive diagnosis. The presence of a monoclonal T-cell population has been reported in several of the inflammatory dermatoses considered in the differential diagnosis of early MF, and serves as a potential diagnostic pitfall. The frequency of T-cell clonality (TCC) in granulomatous dermatitides has not yet been established.
Design: A search of our archives revealed 29 cases of granulomatous dermatitis with biopsies at two distinct sites. We obtained the clinical findings at presentation and long-term follow-up. These findings were correlated with T-cell receptor gamma chain rearrangement by polymerase chain reaction (TCR-PCR) to evaluate for clonality at two separate anatomic skin sites.
Results: Of the 29 cases of granulomatous dermatitis, 17 cases had clinical follow-up (mean range 20 months) and 12 were lost to follow-up. Diagnoses included granuloma annulare (12), sarcoidosis (3), leprosy (2), annular elastolytic granuloma (1), necrobiosis lipoidica (1), necrobiotic xanthogranuloma (1), granulomatous rosacea (1), granulomatous dermatitis, infection vs. drug (7) and histiocytic disorder, NOS (1). Twenty-five of the 29 cases of granulomatous dermatitis were negative for TCC by dual TCR-PCR. One case of necrobiotic xanthogranuloma showed an identical T-cell clone in two different biopsies sites. Three cases of granuloma annulare showed a T-cell clone in only one biopsy site.
Conclusions: These data suggest that dual TCR-PCR is a clinically useful technique in distinguishing granulomatous inflammatory dermatitides from granulomatous mycosis fungoides. The infrequent finding of a T-cell clone in a granulomatous dermatitis underscores the importance of clinicopathologic correlation and clinical follow-up with sequential biopsies in establishing a definitive diagnosis.
Category: Dermatopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 98, Wednesday Afternoon


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