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

Abstract

The initial presentation and natural history of FCTN fit better with a neoplasm than with a hamartoma. Thus, we suggest replacing the term "nevus" with tumor and considering fibroblastic connective tissue tumor (FCTT) as the right denomination of this clinico-pathological entity. FCTTs are difficult to diagnose due to their clinical heterogeneity. Clinical and histological malignant and benign differential diagnoses are discussed.

Agminated fibroblastic connective tissue nevus in a 1‐year‐old boy

“…The clinical heterogeneity of FCTN can also make diagnosis difficult. Bouaoud et al reported congenital FCTN in three infants with unusual features that were suggestive of sarcoma, lipoma, and vascular malformation. In 2016, Downey et al first reported a unique case of FCTN with multiple agminated lesions on the right lower leg of a 5‐month‐old boy, which was diagnosed as agminated FCTN.…”

“…Fibroblastic connective tissue nevus is difficult to diagnose because the differential diagnosis includes a variety of skin tumors, especially dermal fibroblastic mesenchymal neoplasms . The differential diagnosis is detailed in the algorithm proposed by Bouaoud et al Although FCTN was suspected based on the characteristic histologic features, such as poorly demarcated fascicular growth pattern and CD34 immunopositivity, molecular diagnosis was required to rule out dermatofibrosarcoma protuberans (DFSP) .…”

Progressive atrophic indurated plaques in a 16‐year‐old boy

“…1,2 However, agminated variants 3,4 suggestive of sarcoma, lipoma and vascular malformation have also been reported. 5 Histologically, FCTN is characterized by a poorly defined proliferation of bland spindle cells with pale eosinophilic cytoplasm and tapering nuclei, arranged in randomly orientated short intersecting fascicles infiltrating the reticular dermis and the upper subcutis. FCTN is commonly associated with abnormally situated adipocytes within the reticular dermis.…”

Update on Superficial Spindle Cell Mesenchymal Tumors in Children

“…Given this slight morphological distinction and the difference in clinical presentation between adults and children, it is still not clear whether PDF and MLDDH are one and the same lesion or if MLDDH is a congenital/infantile variant of PDF. It is noteworthy that MLDDH tends to extend into the subcutis, making it very challenging to differentiate between MLDDH and FCTN, as recently emphasized in a few case reports [15,16]. Both lesions may show slight infiltration clinically, although FCTN may be more irregular in shape [16].…”

“…The investigators also argued that dendrocytes are known to proliferate during wound healing and that PDF/MLDDH might be reactive lesions related to trauma. Histologically, MLDDH and PDF are indistinguishable [15]. The lesion consists of a superficial dermal spindle and sometimes ovoid cell proliferation, mainly occupying the reticular dermis but occasionally infiltrating the subcutis.…”