Granulomatous mycosis fungoides: A difficult diagnosis

Granulomatous mycosis fungoides (MF) is an unusual histologic variant of cutaneous T cell lymphoma with an incidence estimated at about 6.3% of cases of mycosis fungoides1. Its diagnosis remains challenging, as histology often reveals a predominantly granulomatous infiltrate with little evidence of epidermotropism1,2,3,. Granulomatous MF is often misdiagnosed as granulomatous dermatitis1. We present a review of the literature on treatments of this variant.
We report the case of a 74-year-old female patient who presented to the Princess Alexandra Hospital Dermatology Clinic with a nine year history of a perifollicular, macular erythematous eruption involving her torso and lower limbs (see images). She was referred with a diagnosis of granulomatous dermatitis and, although mycosis fungoides had been considered by previous treating dermatologists, this had never been confirmed. Previous histopathology showed poorly formed granulomas in the superficial dermis, and an inflammatory infiltrate in the dermis of lymphocytes and histiocytes, which is the predominant infiltrate in granulomatous dermatitis. Immunohistochemistry revealed CD4 and CD8 positive T cells. We repeated biopsies, which demonstrated small granulomas in the superficial dermis surrounded by lymphocytes, with a lichenoid tissue reaction and granulomatous and lymphocytic inflammation. Following discussions with the pathologist, it was decided this likely represented cutaneous T cell lymphoma.
This case highlights the importance of considering a diagnosis of granulomatous MF in a patient with an usual eruption and granulomas on histopathology. The five-year survival rate for granulomatous MF is 66% worse than that in classical MF and the average diagnostic delay is 8.4 years1.
1. Kogut M, Hadaschik E, Grabbe S, Andrulis M. et al. Granulomatous mycosis fungoides, a rare subtype of cutaneous T-cell lymphoma. JAAD Case Reports 2015;1:298-302.
2. Gutte R, Kharkar V, Mahajan S, Chikhalkar S, Khopkar U. Granulomatous mycosis fungoides with hypohidrosis mimicking lepromatous leprosy. Indian J Dermatol Venereol Leprol. 2010;76:686-90.
3. Kempf W, Ostheeren-Michaelis S, Paulli M, Lucioni M, Wechsler J, Audring H, AL. Granulomatous mycosis fungoides and granulomatous slack skin. Ar Arch Dermatol. 2008;144:1609-17.

Dr. Natalie Ling