Intradermal nodular fasciitis: a rare lesion analyzed in a series of 24 cases

Nodular fasciitis, a benign myofibroblastic proliferation that usually occurs in the subcutaneous tissues of the upper extremities, trunk, as well as head and neck of young adults, is not widely recognized to arise primarily within the dermis. Here, we examined the clinicopathologic and immunohistochemical features of a series of 24 cases of intradermal nodular fasciitis retrieved from consult files. Clinical follow-up was obtained from medical records and referring physicians. Fourteen patients were females and 10 were males, with age ranging from 8 to 77 years (mean 27.5 y and median 22.5 y). Most patients presented with a rapidly growing painless solitary mass. Grossly, the lesions were solid, nodular, rubbery, or firm (mean size 1.96 cm and median 1.3 cm). Nine cases (37.5%) arose on limbs, 9 cases (37.5%) on the trunk, and 6 (25%) on the head and neck. All tumors were situated primarily in the dermis and were well circumscribed but unencapsulated. One case showed ill-defined margins. The epidermis was ulcerated in 11 cases. All tumors were composed of cytologically bland, uniform plump spindle cells with elongated, tapering nuclei, vesicular chromatin, small nucleoli, and palely eosinophilic cytoplasm, with no significant cytologic atypia or pleomorphism. These cells were arranged in short-intersecting bundles within a focally microcystic myxoid stroma, containing extravasated red blood cells and scattered lymphocytes. Mitoses ranged from 1 to 6 per 10 high-power fields (mean 2.5). All cases examined were diffusely positive for smooth muscle actin. Only one tumor "recurred" locally. No lesion metastasized. In summary, intradermal nodular fasciitis occurs most commonly on the limbs and trunk of young adults, shows morphologic features similar to nodular fasciitis at conventional sites and should not be confused with sarcoma.