Dermoscopic rainbow pattern sign and siascopic features of angiomatoid fibrous histiocytoma

Abstract

Introduction. A case report of a patient diagnosed with angiomatoid fibrous histiocytoma, with rainbow pattern sign on dermoscopy. Case Description. A 31-year-old HIV-negative patient was referred to a tertiary dermatology clinic due to a slow-growing lesion on the right forearm, which bled upon trauma, present for 2 years. Physical examination revealed a blue-grey nodule 11x8 mm in size. On dermoscopy, a central brown structureless area with white structures, peripheral bluegray homogenous area, regular radial streaming, rainbow pattern and crystalline structures were seen. Siascopic examination registered blood displacement with erythematous blush and dermal melanin. Wide local excision and histopathologic investigation were performed. Microscopically, a poorly demarcated tumor of the reticular dermis was seen, with nests of spindle and ovoid cells dispersed within the collagen fibers, Touton giant cells, sparse erythrocyte-filled cystic spaces and abundant hemosiderophages. Diagnosis of angiomatoid fibrous histiocytoma was established, with no recurrence at 6 months follow up. Summary. The rainbow pattern dermoscopic sign present in angiomatoid fibrous histiocytoma – a rare soft tissue neoplasm with histologic features of nodular distribution of ovoid and spindle cells with blood-filled cystic cavities. Few specific clinical and dermoscopic features have been previously described, making early diagnosis challenging. Conclusion. Angiomatoid fibrous histiocytoma (AFH) is a rare tumor of intermediate biological behavior, most commonly occurring in children and young adults. It is difficult to diagnose clinically, with no established dermoscopic criteria. To our knowledge, this is the first description of the rainbow pattern dermoscopic sign for AFH, a feature most strongly associated [...]