Fibroblastic connective tissue nevus: Clinicopathological and immunohistochemical study of 14 cases

Abstract

The differential diagnosis of FCTN is broad and includes hypertrophic scar, dermatofibroma, dermatomyofibroma, pilar leiomyoma, plaque-stage DFSP, CD34-positive plaque-like dermal fibroma, fibroblastic-predominant plexiform fibrohistiocytic tumor, lipofibromatosis, superficial desmoid fibromatosis and fibrous hamartoma of infancy, of which it represents probably the monophasic variant.

Congenital fibroblastic connective tissue nevi: Unusual and misleading presentations in three infantile cases

“…In patient 1 there was an uncommon infiltration of the entire thickness of the subcutis with focal infiltration of the periosteum, which has never been reported. In patients 1 and 2, we report a superficial infiltration into the subcutis; this infiltration is also reported in 31 (67%) cases from the literature . In addition to CD34 positivity of the fibroblastic lineage, all other markers for spindle cells such as S100P, SMA, desmin, and myogenin were negative, except for a moderate focal SMA positivity in patient 3.…”

“…The overlying epidermis was normal histologically in all the cases we report, as opposed to the papillomatous epidermic pattern described in several cases . As in all cases reported (n = 46) in the literature, we did not find cellular atypias or mitoses; adnexal structures were entrapped but always spared . In patient 1 there was an uncommon infiltration of the entire thickness of the subcutis with focal infiltration of the periosteum, which has never been reported.…”

“…In addition to CD34 positivity of the fibroblastic lineage, all other markers for spindle cells such as S100P, SMA, desmin, and myogenin were negative, except for a moderate focal SMA positivity in patient 3. Focal SMA positivity has been reported in 17 of 37 examined cases …”

“…Age at presentation is variable; in the largest and original series describing the first 25 FCTN cases, the age range was 1 month to 58 years (median 10 years) . In the second largest series available in the literature (14 patients), age ranged from 1 to 56 years . Other smaller series and case reports have described patients at various ages: one case at 1 month old; one case at 5 months old; one case at 9 years old; three cases at 10, 24, and 32 years old; and one case at 15 years old .…”

“…In brief, histology of FCTN shows poorly circumscribed lesions situated in the reticular dermis and commonly extending into the superficial subcutis. FCTN are composed of irregularly distributed fascicles of bland spindled cells and are defined according to a list of fundamental features: no atypia, pleomorphism, or mitotic activity; skin appendages entrapped but unaffected; and no evidence of malignancy. In most cases, CD34 is positive, but in some cases, cells can express SMA or are CD34– and SMA– .…”