Fibrous umbilical polyp: a distinct fasciitis-like proliferation of early childhood with a marked male predominance.

Benign fibrous lesions of the umbilicus have not been previously studied in a formal series. Clinical and pathologic findings were reviewed in all patients under age 19 with lesions resected from the umbilical region at Children's Hospital (Boston, MA, USA) during an 8-year period. Fourteen lesions were characterized by a well-circumscribed dome-shaped or pedunculated dermal proliferation of moderately cellular fibrous tissue without significant inflammation. Fibroblastic cells were plump to elongate with abundant pale pink cytoplasm. In a subset of lesions, some cells showed atypia or ganglion cell-like morphology. Collagen ranged from sparse to long narrow bundles. Vascularity was sparse and the lesions were nonencapsulated. Loss of rete ridges and basket-weave hyperkeratosis was common in the overlying epidermis. Immunostaining showed focal staining for muscle-specific actin and desmin in a subset of cases and no staining for cytokeratin, epithelial membrane antigen, CD34, or S-100. Age ranged from 3 to 18 months (mean 9 months, median 8 months). Thirteen (93%) patients were boys. Recurrence was not observed. In conclusion, the "fibrous umbilical polyp" is a distinctive lesion of early childhood with an uncertain pathogenesis. It shows a marked predilection for boys, is not rare, and appears to represent a clinicopathologic entity. Perhaps the umbilicus, a midline defect that is normally filled by dense scar tissue after birth, contains unique fibrogenic factors responsible for the development of this distinct lesion.