CD7 Expression in Differentiating Mycosis Fungoides from Benign Cutaneous Lymphocytic Infiltrates

Background: diagnosis of the early phase of mycosis fungoides(mf) is sometimes difficult. loss of cd7 expression isconsidered a distinguishing characteristic of mf. the aim ofthis study was to determine the range of cd7 expression inmf and compare the results with benign inflammatory dermatosisand equivocal cases of possible mf.methods: during a period of 30 months, we examined 15 patientswith mf, 12 patients suspicious for mf, and 15 patientswith benign inflammatory dermatosis. the slides stained byh&e were reviewed by two pathologists. immunostaining wasdone for cd43, cd3, cd5, cd7, and cd20 on paraffin embeddedtissues.results: all the patients in mf group showed absence of cd7expression in epidermotropic mycosis cells. compared with benigninflammatory dermatosis, patients with mf had significantlylower cd7 expression in the dermal infiltrate (p< 0.0001). inpatients with mf, the mean cd7 was significantly lower thancd43, cd3, and cd5 (p=0.001). the mean cd7 count of parapsoriasiswas significantly higher than mf (p= 0.01). the meancd7 count of parapsoriasis was significantly lower than benigninflammatory dermatosis (p=0.016). the lowest mean cd7counts were found in patch stage of mf. low cd7 expression <10 % lymphocytes had sensitivity and positive predictive valuesof 75% and 100% and specificity and negative predictive valuesof 100% and 83.3% for the diagnosis of patch stage ofmf.conclusion: minimal expression of cd7 is a specific findingfor patch stage of mf. benign inflammatory dermatosis canalso show low expression of this marker , but rarely matchesthat of patch stage of mf.