Primary cutaneous anaplastic large cell lymphoma with leg involvement: A case report and review of 11 cases

conjunction with histopathologically rich cellularity and frequent mitotic figures, often mislead physicians to suspect malignant tumors. Therefore, recognition of this condition is critical to avoid unnecessary treatment. Infantile fibrosarcoma is a condition that affects newborns and infants. Histopathologically, infantile fibrosarcoma is composed of fascicles of relatively uniform spindle cells in a herringbone pattern. Yebenes et al. discuss the immunohistochemical differential diagnosis of cranial fasciitis. However, the immunohistochemical characteristics of cranial fasciitis are shown to be almost the same as those of infantile fibrosarcoma, suggesting difficulty of histopathological differentiation. ETV6–NTRK3 fusion is found in almost all cases of infantile fibrosarcoma, and is now considered to be the most reliable molecular genetic marker distinguishing other fibrotic lesions of childhood. Other conditions, which are sometimes difficult to distinguish from infantile fibrosarcoma, such as infantile myofibromatosis or rapidly involuting congenital hemangioma, have been shown to be differentiated by this genetic approach. ETV6–NTRK3 fusion can be established by RT–PCR and ⁄or FISH in paraffinembedded tissue sections. But liquid phase RT–PCR from paraffin-embedded sections may have pitfalls compared to the tests from frozen sections, and may result in false negativity. Our case also had irrelevant results by paraffin-based RT–PCR. FISH is a more precise way to detect the ETV6–NTRK3 fusion, and when one sees a case with cranial fasciitis, which is difficult to discern from infantile fibrosarcoma, these genetic approaches may solve the question with reliance. Shinichi IMAFUKU, Akira TAKAHASHI, Yuka HASHIZUMI, Kiyohito SASAMOTO, Ryota TOKUMARU, Hiroshi IWASAKI, Juichiro NAKAYAMA Departments of Dermatology and Pathology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan