cording to histopathological characteristics. One is composite tumor, and the other is collision tumor. Composite tumor is a lesion showing the combined histopathological characteristics of two or more previously recognized tumor and/or cysts of different categories. Two constituent parts are mixed with each other, and histological transition is often observed. On the other hand, collision tumor is a lesion showing the independent histopathological characteristics of two or more previously recognized tumor and/or cysts of different categories. Two constituent parts are separated each other by connective tissue, and histological transition is not observed. Their origin is still unclear. In this study, a collision tumor was reported. 77-year old woman was referred to CNUH with a neck mass in right submandibular area. Incisional biopsy was carried out, and the patient was diagnosed as collision tumor of squamous cell carcinoma and neurofibroma. After reviewing studies reporting collision tumor from head and neck area, formation of a collision tumor was most frequent from a cervical area and average age is 59.6. A collision tumor commonly lead to misdiagnosis, and the prognosis is not always transparent. The variety symptom of collision tumor has to be kept in mind in the diagnosis and treatment of the lesions in head and neck area.

We present a case of intraparotid plexiform neurofibroma in a 7-year-old man. The lesion was determined as plexiform neuroma in histopathological findings, but final diagnosis was plexiform neurofibroma considering his familiy history of neurofibromatosis and café au lait spots on his body. Currently we are executing follow-up after removing the tumor with surgery. Plexiform neurofibroma can develope at any point along a nerve and spread out either just under the skin or deeper in the body. According to the literature, the most common site of plexiform neurofibroma is mouth and face in the head and neck region. Also, plexiform neurofibroma occurs at 8.8-year-old in neurofibromatosis typeⅠ patient with familial history. Because of interlacing with adjacent normal tissue and the invasive nature we have difficult resecting the mass completely. So when the tumor turns symptomatic or disfiguring leading to an aesthetic problem, surgery had better be undertaken.

Neurotized melanocytic nevus (NMN) is categorized into intradermal/intramucosal type of acquired melanocytic nevus. In contrast to typical intramucosal nevus which has relatively distinct histological features, the diagnosis of NMN requires more attention due to its mimicry of benign neural tumors such as neurofibroma. The majority of lesional cells, NMN cells, showed a spindle cell morphology and abundant, eosinophilic cytoplasm which were positive for S-100, vimentin, and collagen type IV. Positive reaction for MART-1 was detected in the NMN cells as well as in the epithelioid nevus cells beneath the epithelium. Neurofibroma exhibited diffuse positivity for S-100, vimentin, CD34 and collagen type IV, but never expressed MART-1. Toluidine blue stained the numerous mast cells scattered in the lesion of neurofibroma, compared to the relatively minor detection of mast cells in NMN. Therefore, MART-1 is a useful marker in differentiating NMN from neurofibroma.