Hypopigmented mycosis fungoides: An enigmatic underdiagnosed entity

Summary: Mycosis fungoides (MF) is most common cutaneous T-Cell lymphomas (CTCL) ,accounting for 4% extranodal non-Hodgkin Lymphomas. Hypopigmented mycosis fungoides (HMF) commonly affects children and adolescent age group with incidence of 0.17/100 biopsies (15/8500) in Indian population.It presents as hypopigmented patch and plaque over trunk, back, and limbs . Material and methods: All biopsies of MF were retrieved retrospectively over 10 years. A detailed clinical, morphological and immunohistochemical findings were analysed. Differential diagnosis included vitiligo, progressive macular hypomelanosis, pityriasis lichenoid chronicus, hypopigmented sarcoidosis, and CTCL Results: A total of 255 cases of MF were reported of which 12 were diagnosed as HMF. There were, 3 children, 6 young adults, and 3 older age group. Histopathology revealed epidermotropism and pautriers micro-abscess in 3 cases. On IHC, atypical cells were CD3 & CD5 positive and CD7 was downregulated in all 12(100%) cases. CD8 was positive in 7/12 cases whereas 2 cases were negative. The CD4 IHC had reduced expression in 4 cases. Conclusion: Confirmation of Hypopigmented MF needs a biopsy with IHC or T cell gene rearrangement. Contrary to literature HMF can be seen in adults and requires a strong index of clinical suspicion in hypopigmented patch/plaque irrespective of age for its diagnosis.