DP22: A challenging case of granulomatosis mycosis fungoides masquerading as cutaneous sarcoidosis

Su Xin Lim,¹ Joelle Dobson,¹ Laszlo Igali,¹ Catherine Stefanato,² Mary Wain,² Marianna Philippidou,³ Duncan Mhairi,³ Sarah Walsh³ and Puran Gurung¹

¹Norfolks and Norwich University Hospital, Norwich, UK; ²Guy’s and St Thomas’ Hospital, London, UK; and ³King’s College Hospital, London, UK

We present a case of granulomatous mycosis fungoides (GMF), initially diagnosed as cutaneous sarcoidosis. A 44-year-old woman presented with a 2-year history of an eruption on her trunk and neck. She described that the initial patches had gradually thickened over 2–3 months and were intermittently pruritic. She reported night sweats, which she considered perimenopausal. Direct questioning did not reveal respiratory or ocular symptoms, or a recent travel history. Her past medical history included breast implants 13 years previously. Examination demonstrated erythematous hyperpigmented plaques on her back and the nape of the neck with no lymphadenopathy or organomegaly. The differential diagnosis included cutaneous sarcoidosis, interstitial granuloma annulare or a granulomatous reaction to leaked breast implant material. An incisional biopsy demonstrated a dermal infiltrate of non-necrotizing granulomata with multinucleated giant cells. Clinicopathological correlation led to a diagnosis of cutaneous sarcoidosis. Further investigations (serum angiotensin-converting enzyme, calcium profile, tissue mycobacterial cultures and computed tomography of the chest, abdomen and pelvis) were normal. The breast surgeons confirmed the implants were intact. The case was discussed at our regional meeting. A repeat biopsy showed similar findings and was reported to be consistent with sarcoidosis with the subcutaneous substance to some of the lesions raising the suspicion of Darier-Roussy sarcoidosis. The patient was commenced on a tapering regimen of prednisolone 40 mg once daily with hydroxychloroquine 200 mg twice daily. The nodules rapidly flattened. However, steroid weaning prompted recrudescence of the lesions. Methotrexate was introduced as a steroid-sparing agent, with an incomplete response. She was referred to a tertiary sarcoidosis service. Here, the clinical appearance was considered atypical for sarcoidosis and her serum soluble interleukin-2 receptor assay (IL-2RA) was normal. A further skin biopsy was performed, which revealed a scattered infiltrate of cytologically atypical lymphoid cells in the epidermis; she was referred to the regional cutaneous lymphoma service where further immunostaining (CD2⁺CD3⁺CD4⁺CD5⁺CD7^–CD8^–CD30⁺) and clonality studies (clonal on T-cell receptor gene analysis) confirmed the diagnosis of GMF. Positron emission tomography/computed tomography was normal, confirming stage 1A (T1B) disease. Our patient has received superficial low-dose radiotherapy to the lesions and remains on treatment with methotrexate. GMF is a rare but distinct clinical subtype of mycosis fungoides, representing approximately 2% of cutaneous lymphoma. Histologically, the prominent granulomata can obscure neoplastic lymphocytes and resemble sarcoidosis. The absence of epidermotropism in almost half of cases may further obscure the diagnosis. Our case illustrates the diagnostic challenge of granulomatous lymphoma, and the need for repeat skin biopsies where therapeutic response is not as anticipated or in atypical presentations.