Transient homonymous hemianopia and positive visual phenomena in patients with nonketotic hyperglycemia.

is a male-female predilection of 2:1. It has been described as freely mobile, well circumscribed, and subcuticular. Although the clinical characteristics of fibrous hamartoma have been variably reported, it has unique microscopic features. All prior cases consistently report well-defined traversing bundles of dense fibrocollagenous tissue, immature loose-textured mesenchyme, and increased areas of interspersed mature adipose tissue. It has been postulated that the mesenchymal tissue has vasoproliferative capability, which may explain the presence of an angioma involving the adjacent conjunctiva in this patient. In our case, the overall histopathologic pattern, with the focal basaloid budding overlying a circumscribed nodule, suggests the diagnosis of dermatofibroma. However, the elements making up the tumor are much more characteristic of a fibrous hamartoma. Diffuse immunoreactivity for CD34 is suggestive of a solitary fibrous tumor. The negative reactivity to factor XIIIa and muscle-specific actin rules out dermatofibroma and confirms the diagnosis of fibrous hamartoma of infancy. The basaloid hyperplasia overlying the fibrous hamartoma can be explained on the basis of activation of keratinocytes. The presence of primitive mesenchymal cells in the underlying nodule may mediate the release of cytokines and growth factors that stimulate the keratinocytes. This leads to a cascade of events that may be responsible for the basaloid budding of the epidermis. A similar mechanism has been described in dermatofibroma. Other rare entities in the differential diagnosis include myofibroma, lipofibromatosis, and calcifying aponeurotic fibroma. Myofibromas are found in the head and neck region and have light-staining areas and dark, more hemangiopericytomalike staining areas histologically. The negative reactivity to musclespecific actin in our specimen rules out myofibroma. Lipofibromatosis consists of abundant adipose tissue traversed by bundles of fibroblasts, without immature mesenchyme. Calcifying aponeurotic fibroma is found interspersed with fat in infants and is composed of calcific areas surrounded by hyalinized collagen and fibroblasts. The natural history of fibrous hamartoma suggests initial growth that slows with older age. No malignant degeneration or spontaneous regression has been documented. Local surgical excision is successful in most cases, with recurrent growth occasionally noted after incomplete excision. Fibrous hamartoma is a rare, benign entity that occurs in infants and young children. It rarely involves the face. The lesion can be successfully excised, and its unique histopathologic characteristics are valuable in confirming the diagnosis.