Vitiligo vs. hypopigmented mycosis fungoides (histopathological and immunohistochemical study, univariate analysis).

Vitiligo is a common skin disease characterized by the presence of well circumscribed, depigmented milky white macules devoid of identifiable melanocytes. On the other hand, hypopigmented mycosis fungoides (MF) is a rare variant of MF which presents clinically as persistent hypopigmented macules and patches. Both disorders show a predominance of CD8+ T cells in tissue samples and hence the differentiation between the two diseases on clinical, histopathological and even immunohistochemical grounds may offer great difficulty. The aim of this work is to identity certain histopathological clues which might help to differentiate between the two diseases. The study included 54 patients (26 vitiligo patients and 28 patients with Hypopigmented MF). Skin biopsies were taken and examined by hematoxylin and eosin and CD3, CD4 and CD8 markers were performed for ten vitiligo and nine MF patients. We have found that epidermotropism, hydropic degeneration of basal cells, partial loss of pigment, preservation of some melanocytes, presence of lymphocytes within the papillary dermis, increased density of the dermal infiltrate and wiry fibrosis of the papillary dermal collagen were detected with a significantly higher incidence in hypopigmented MF rather than vitiligo (P-values < 0.0001, < 0.00011, < 0.00011, = 0.001, = 0.008 and = 0.001 respectively). On the other hand, focal thickening of the basement membrane, complete loss of pigmentation, total absence of melanocytes, as well as absence or sparsness of lymphocytes in the dermal papillae were seen much more frequently in vitiligo. Statistical analysis of these differences was significant with P-values < 0.00011, < 0.00011, < 0.00011, = 0.008 respectively, regarding these pathological criteria. We conclude that differentiation of hypopigmented MF from vitiligo is possible by relying on the histopathological clues described in this study. This is particularly useful in areas of the world where cost benefit is crucial.