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Path Quiz Case-3: Diagnosis-
Path Quiz Online:CASE
HISTORY AND IMAGE: |
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| April
2008
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This tumour was previously known as 'subdermal fibromatous tumour of infancy'. It was called 'fibrous hamartoma of infancy' by Enzinger in 1965. Age : Usually occurs in the first two years of life. The tumour may be present since birth or in some cases present in older children. Site : Shoulder, axilla, neck and upper arm. Cases have been reported in the perianal area, scrotum and the inguinal region. Clinical presentation: Presents as a painless solitary ,at times rapidly growing nodule. Multiple lesions have been reported. There is a male predominance of 3:1. The clinical course is benign, despite its infiltrative appearance and tendency to recur. The tumour shows no evidence of malignant transformation . Gross appearance: Firm circumscribed poorly defined fibro-fatty tissue usually present in the deep dermis and subcutis. Cut surface has a glistening gray-white appearance interspersed with fatty tissue. The involved area measures 2- 8 cm in maximun diameter.
Microscopic features :
Image
Link1 The tumour has a poorly defined margin. There are some reports of older lesions showing some encapsulation. The lesion is centred on the subcutis. The three main components are: 1.Interlacing trabeculae of dense fibrocollageneosu tissue. Finger like projections of fibrous tissue extend into the fatty tissue. 2.Small round to ovoid nests of undifferentiated spindle or stellate cells set in a myxoid stroma containing delicate vessels. The mucoid matrix is Alcian blue positive. Sparse lymphocytes may be present in the stroma. 3. Interspersed mature adipocytes. The fat tissue varies from case to case and is much greater than normally present in the subcutis. Extension into underlying tissue, like muscle or fascia, is a known feature, but visceral involvement has not been reported.
Immunohistochemistry :
Routine hematoxylin-eosin stained sections
are generally sufficient for a diagnosis, but immunochemistry may be
useful. The primitive mesenchymal cells are vimentin positive, the
fibroblastic component is desmin and smooth muscle actin positive and the
adipocytes are S100 protein positive.
Differential diagnosis:
2. Infantile digital fibromatosis: Occurs almost exclusively in the fingers and toes. These tumor cells are characterized by intracytoplasmic perinuclear eosinophilic inclusions. 3. Calcifying aponeurotic fibroma: This lesion shows characteristic histologic pattern called zonation - Calcific areas are surrounded by hyalinized collagenous foci, which in turn are palisaded by plump fibroblasts. This tumour may not exhibit foci of calcification in its earliest phase and often infiltrates fat in infants and young children. The absence of immature mesenchyme and trabecular arrangement of fibroblasts distinguishes this from fibrous hamartoma of infancy. Calcifying aponeurotic fibroma: a clinicopathologic study of 22 cases arising in uncommon sites.Hum Pathol. 1998 Dec;29(12):1504-10 4. Myofibromas: This lesion is commonly found in the head and neck region and trunk. Histologically, the lesion appears biphasic with alternating light- and dark-staining areas. The dark-staining areas are composed of bundles of myofibroblasts exhibiting a hemangiopericytoma-like pattern. 7. Nodular fasciitis: This lesion is rare in children, circumscribed with abundant proliferation of plump fibroblasts , frequent mitoses and extravasated erythrocytes. 8.Dermatofibrosarcoma protuberans (plaque form): Early to middle adult life. Characterized by uniform slender fibroblasts in a storiform pattern, areas of higher mitotic activity with nuclear atypia. Immunohistochemistry - CD34: positive
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