SUBDERMAL FIBROUS HAMARTOMA OF INFANCY - PATHOLOGY OF 40 CASES AND DIFFERENTIAL-DIAGNOSIS

Forty subdermal fibrous hamartomas of infancy occurred in 29 males and 11 females who were 7 months to 4 years of age at surgery. At least 4 were congenital. The lesions were situated in axilla, chest wall, and breast (17 cases); abdominal wall, inguinal region, and scrotum (8); buttock and lower limb (6); upper limb (4); neck and scalp (3); and lo w back (2). They were 0.7 to 10 cm, ill defined, and five underwent re excision, which was curative in all. All had the characteristic mixtur e of fibrous and adipose tissue and nests of immature mesenchyme in di fferent proportions, and nearly all showed lymphocytes and thick paten t capillaries in the mesenchyme. However, the fibrous component varied considerably in amount, pattern, and cellularity, so that lesions tha t were typical in some areas, in others resembled collagenizing vascul ar granulation tissue, deep fibrous histiocytoma, or fibromatosis. Tho se in which adipose tissue predominated were distinguished from fibrol ipoma by foci of immature mesenchyme and from lipoblastoma by their la ck of a capsule and of a lobular pattern.