Introduction Oral mycosismgugoid (MF) is a rare manifestation of cutaneous T-cell lymphoma (CTCL), which is not considered due to its rarity. Early diagnosis requires a thorough examination of the oral cavity in all MFs and histopathological evaluation of any suspicious lesions. In this study, a patient with oral MF, its course, prognosis and treatment is discussed. Clinical Presentation A 41-year-old male was referred to the dermatology department of Razi Hospital, Tehran, Iran in April 2011. He complained of a long-term history of pruritus and xerosis, all over the body especially the trunk and lower extremities. He has been treated over the years with emollient-based topical steroid cream with partial response. Six months prior to this visit, the observed symptoms and signs had progressed to erythematous, finely scaly patches on the trunk, lower extremities, and forehead, accompanied by an ulcerated tumor on the right shoulder and erosive leukoplakia of the hard palate. Biopsies of the skin and mucosal lesions were the same and showed diffuse infiltration of mixed small to medium sized cells in the dermis with moderate degree of atypia and an interface pattern at the dermoepidermal junction (fig. 1). Immunohistochemical (IHC) studies showed positive staining for CD3 and CD4 and negatively for CD8, CD20, and CD30. The monoclonal T cell receptor rearrangement was detectable by PCR. The results of skin and mucosal biopsies, IHC, and PCR were in favor of MF. A thorough physical examination highlighted generalized patches affecting more than 10% of the total skin surface and the known tumor lesion on the shoulder and erosive leukoplakia of the palate (fig. 2). No swollen lymph nodes were found. CT scan of the chest and abdomen normal, bone marrow biopsy normal... in the center of the document... gh unsatisfactory (5). In our patient, the oral manifestation after several months instead of years, represented an aggressive MF, and the progression under chemotherapy, caused incomplete cycles of CHOP (3 cycles instead of 6) which was replaced by TSEB only for palliative therapy. The similarity between the mortality rate of oral and visceral involvement in MF (average survival less than 1 year), places oral MF as an advanced disease with poor prognosis (1). Due to its rarity, oral MF may be missed by examination. Early diagnosis of this manifestation is of great importance for the effectiveness of chemotherapy, compared to late identification. Our patient once again emphasized the importance of a complete physical examination with particular attention to the oral cavity in MF. To the best of our knowledge, this is the first reported case of oral involvement in MF, originating from Iran.