Fibroblastic Connective Tissue Nevus: A Rare Cutaneous Lesion Analyzed in a Series of 25 Cases

[Pediatric cutaneous mesenchymal tumors: How to cope with small samples?]

This review article deals with the diagnosis of superficial mesenchymal tumours in children. This is not a comprehensive review, but it focuses on the issue of diagnosis on small samples, especially on fine needle biopsies, which are more and more frequent. A selection of difficult diagnostic situations are discussed, including the case of spindle-cell tumours with variable adipocytic component, some fibrohistiocytic tumours, myofibromas, and vascular tumours. The key messages are the technical requirements in relation to the small sample size, the essential nature of clinical data in paediatric pathology and primarily the age, which is crucial not only for establishing the differential diagnosis but also for choosing the relevant ancillary techniques, and last, the utility of cytogenetics, mainly FISH, and of wisely used molecular biology techniques.

Asymptomatic CD34+ plaque on the scalp of a child

Fibroblastic connective tissue nevus (FCTN) is a rare, benign dermal mesenchymal lesion of fibroblastic and myofibroblastic lineage. We report a case of a 2-year-old male who presented with an 18-month history of an erythematous, asymptomatic, unchanging dermal plaque on the right medial frontal scalp. A punch biopsy showed a disorderly, bland, dermal fibroblastic spindle cell proliferation extending to the superficial subcutis. It stained positive for CD34, and concern for dermatofibrosarcoma protuberans was raised. However, FISH was negative for PDGFB rearrangement, and the constellation of findings was most consistent with FCTN. This case underscores the importance of distinguishing CD34+ mesenchymal tumors for both dermatologists and dermatopathologists. As these represent a rather diverse group of lesions with different biological behaviors, a knowledge of the differential diagnosis of these entities is critical for proper patient management.

Giant congenital fibroblastic connective tissue nevus associated with vascular anomalies

We described an unusual combination of fibroblastic connective nevus (FCTN) already present at birth with underlying vascular anomalies. Overall, the lesion appeared as a large purplish-brown mass in the groin region up to the third of the right thigh, with partial spontaneous regression during the first three months of life. The FCTN observed exhibited several unusual characteristics: it was congenital, large in size, and located in the lower limbs. Finally, it represented the first case described in which an FCTN arose in association with vascular anomalies.

An Asymptomatic Brown Plaque on the Face: A Quiz

Abstract is missing (Quiz)

Infantile Fibrosarcoma and Other Spindle Cell Neoplasms of Infancy. A Review of Morphologically Overlapping yet Molecularly Distinctive Entities

BACKGROUND

Regardless of age at presentation, many soft tissue neoplasms have overlapping histopathologic and immunophenotypic features to serve as a diagnostic challenge.

CASE REPORT

We reported a case of a spindle cell neoplasm in an infant, which was initially considered a vascular anomaly clinically and an eventual biopsy revealed marked inflammation with a spindle cell component that was resolved as an infantile fibrosarcoma with an ETV6 break-apart.

CONCLUSION

The context of this case lead to a further consideration of various other spindle cell neoplasms arising predominantly in the soft tissues during the infancy period as defined by the first two years of age. Though sharing similar morphologic features, these tumors can be categorized into several molecular genetic groups, which have provided both diagnostic and pathogenetic insights as well as treatment options in some cases.

Fibroblastic Connective Tissue Nevus Mimicking Lipoma on Ultrasound: Case Report and Brief Review

Fibroblastic connective tissue nevus (FCTN) is a rare, benign, and recently described dermal mesenchymal lesion characterized by CD34-positive spindle cells. We present a case of FCTN on the upper back of a 9-month-old boy who was diagnosed with a benign lipoma by ultrasound.

Two cases of congenital dermatomyofibroma

We present two infants with histologically confirmed congenital dermatomyofibromas. Congenital cases are rare with only one prior case reporting presence since birth. Given the benign nature of the lesions and propensity of dermatomyofibromas to resolve without intervention in young male patients, no additional treatments were pursued.

Plexiform Myofibroblastoma: Clinicopathologic Analysis of 36 Cases of a Distinctive Benign Tumor of Soft Tissue Affecting Mainly Children and Young Adults

The spectrum of benign superficial fibroblastic/myofibroblastic tumors continues to expand and includes entities such as plexiform fibrohistiocytic tumor, dermatomyofibroma and fibroblastic connective tissue nevus. Here, we describe a seemingly distinctive group of lesions which we have labeled "plexiform myofibroblastoma" (PM). PM is a rare superficial mesenchymal tumor of fibroblastic/myofibroblastic lineage that predominantly occurs in children and young adults. Thirty-six cases from the consultation archives of one of the authors have been studied to characterize the clinicopathologic characteristics of PM. 19 patients (53%) were female and 17 were male, with age at presentation ranging from congenital (2 cases) to 50 years of age (median: 9.5 y). Three patients had multiple lesions. Males tended to develop tumors during childhood (median: 2 y; range: congenital-37 y), while in females the age distribution was relatively uniform from childhood through adulthood (median age: 25 y; range: 4 mo to 50 y). Most tumors occurred in truncal locations (25/40), including the back (11), anterolateral chest wall (4), axilla (4), abdominal wall (4), perineum (1) and suprapubic region (1). Other tumor sites were the neck (10/40), occiput (2), lower extremity (2) and breast (1). The average greatest dimension was 2.7±1.7 cm (range: 0.6 to 8 cm). Three male patients, 2 of whom were brothers, presented between 6 months and 1 year of age with multiple lesions variably involving the back, occiput and axillae; these lesions spontaneously regressed after being present for about 2 years, with no evidence of recurrence at a mean follow-up of 11.4±3.2 years. Histologically, PM was composed of plexiform fascicles of fibroblastic/myofibroblastic spindle cells that ramify through the subcutis and reticular dermis. The bland neoplastic cells had indistinct cell borders, palely eosinophilic cytoplasm and ovoid or tapered nuclei. There was no histiocytoid component in any case, and no cases contained osteoclast-like giant cells. Twelve of thirty-four (35%) reviewed cases showed at least focal keloidal hyalinization, 6/34 (18%) contained somewhat fasciitis-like areas and 6/34 (18%) contained focal myxoid stroma. Immunohistochemical studies were positive for SMA (27/32 cases), desmin (9/21) and CD34 (13/24) and negative for β-catenin (0/14) and S-100 (0/22). EMA was weakly positive in 2/15 cases. An FGFR2 M535L tyrosine kinase domain variant of unknown significance was detected in 1/7 sequenced cases, and no somatic alterations, copy number alterations or gene fusions were detected in the other 6. Clinical follow-up data were available for 16/36 patients (44%; median duration: 5.5 y). Although most excisions had positive margins (11/16), only 1 patient developed a local recurrence 4 years after initial excision. No tumors metastasized. PM is a benign tumor with characteristic histology, epidemiology and anatomic site distribution. Because PM rarely recurs, a watchful waiting approach would be reasonable for lesions excised with positive margins.

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

Fibroblastic connective tissue nevus (FCTN) is a benign cutaneous mesenchymal lesion characterized by proliferation of CD34-positive fibroblastic/myofibroblastic spindle-shaped cells. We report a case of agminated FCTN on the right lower abdomen of a 1-year-old boy.

Medallion-like dermal dendrocyte hamartoma: A rare congenital CD34-positive dermal lesion clinically and pathologically overlapping with fibroblastic connective tissue nevus

Both medallion-like dermal dendrocyte hamartoma and fibroblastic connective tissue nevus are rare benign dermal lesions composed of CD34-positive spindle cells. Although regarded as different diseases, it is sometimes difficult to distinguish between them due to their clinical and pathological similarities. We present a case of medallion-like dermal dendrocyte hamartoma that could also be diagnosed as fibroblastic connective tissue nevus and propose the possibility of overlap in these diseases.

Hamartomas of skin and soft tissue

Hamartomas are benign lesions composed of aberrant disorganized growth of mature tissues. Choristomas are similar, except that they are composed of tissues not normally found at the anatomic site in which the lesion is arising. A wide range of hamartomas and choristomas can arise in the skin and soft tissue. Some of these may cause diagnostic difficulty and potentially be mistaken for neoplasms. Some neoplasms may resemble hamaratomas. Here we review the current clinical and pathologic features of these lesions, both common and rare, and discuss how to distinguish them from other entities in the differential diagnosis.

Novel KHDRBS1-NTRK3 rearrangement in a congenital pediatric CD34-positive skin tumor: a case report

Cutaneous spindle-cell neoplasms in adults as well as children represent a frequent dilemma for pathologists. Along this neoplasm spectrum, the differential diagnosis with CD34-positive proliferations can be challenging, particularly concerning neoplasms of fibrohistiocytic and fibroblastic lineages. In children, cutaneous and superficial soft-tissue neoplasms with CD34-positive spindle cells are associated with benign to intermediate malignancy potential and include lipofibromatosis, plaque-like CD34-positive dermal fibroma, fibroblastic connective tissue nevus, and congenital dermatofibrosarcoma protuberans. Molecular biology has been valuable in showing dermatofibrosarcoma protuberans and infantile fibrosarcoma that are characterized by COL1A1-PDGFB and ETV6-NTRK3 rearrangements respectively. We report a case of congenital CD34-positive dermohypodermal spindle-cell neoplasm occurring in a female infant and harboring a novel KHDRBS1-NTRK3 fusion. This tumor could belong to a new subgroup of pediatric cutaneous spindle-cell neoplasms, be an atypical presentation of a plaque-like CD34-positive dermal fibroma, of a fibroblastic connective tissue nevus, or represent a dermatofibrosarcoma protuberans with an alternative gene rearrangement.

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

BACKGROUND

Fibroblastic connective tissue nevi (FCTN) are benign skin conditions characterized by bland spindle cells infiltrating the reticular dermis and the upper subcutis with preservation of adnexal structures. A subset of FCTN expresses CD34, which may cause difficulties in the differential diagnosis, in particular with dermatofibrosarcoma (DFSP). We aim to study clinical and histological main features of congenital FCTN to better understand their heterogeneity.

METHODS

We present 3 cases of congenital FCTN with misleading pseudo-tumoral presentations and compare them with published cases in literature. We provide a diagnostic algorithm for congenital neonatal connective tissue tumors.

RESULTS

Clinically, FCTN mostly present as well-limited and nontender plaques or nodules mainly located in the neck and face areas or in the trunk. Histologically, FCTN are composed of irregularly distributed fascicles of bland spindled cells and are defined by a list of fundamental features: (i) no atypia, pleomorphism, or mitotic activity; (ii) skin appendages entrapped but unaffected; (iii) no evidence for malignancy. In most cases CD34 is positive, but in some cases, cells can express SMA or are even CD34- and SMA-.

CONCLUSION

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.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

[Extensive connective tissue nevus in children]

BACKGROUND

Connective tissue nevus (CTN) is a rare condition of the extracellular matrix components that generally presents as papulae of normal skin colour. This condition may be syndromic or sporadic.

PATIENTS AND METHODS

We report herein two isolated cases of extensive and infiltrative CTN in children at risk for subsequent joint stiffening. The pathology samples displayed respectively mixed hamartoma and a collagenoma.

DISCUSSION

The onset of these lesions is often difficult to establish, since they are usually unnoticeable at first. When confronted with extensive CTN, the main differential diagnoses are eosinophilic fasciitis and morphea, and these must be ruled out by skin biopsy. CTN is associated with osteopoikilosis in Buschke-Ollendorf syndrome. Skeletal lesions are asymptomatic and are detected by means of iterative X-ray. Their management comprises symptomatic care.

Congenital Atrophic Plaque: Fibroblastic Connective Tissue Nevus

Fibroblastic connective tissue nevus (FCTN) is a rare, benign, dermal mesenchymal hamartoma that affects children. We report a 15-year-old boy with a congenital FCTN and describe the clinical, dermatoscopic, and histopathologic features.

Evolution of Fibroblastic Connective Tissue Nevus in an Infant

Fibroblastic connective tissue nevus (FCTN) is a rare and recently described neoplasm of fibroblastic/myofibroblastic lineage. We report a case of a 1-month-old healthy male infant who presented with a dermal plaque on the upper chest since birth. A punch biopsy demonstrated a dermal spindle-cell neoplasm with variable smooth muscle actin positivity and negative staining for CD34, consistent with myofibroma. Over the course of the next year, the remaining lesional tissue exhibited clinical softening and a surgical excisional specimen revealed histologic findings distinct from the original biopsy. These included a poorly circumscribed proliferation of bland spindle cells arranged in short fascicles centered in the dermis and extending into the subcutis with positivity for CD34, and absence of staining with smooth muscle actin features diagnostic of FCTN. Our case allowed the opportunity to see this unusual neoplasm at different stages, and we hypothesize that FCTN may undergo an early cellular phase and that time is required for these lesions to "mature" and demonstrate the more characteristic features of FCTN.

Agminated Fibroblastic Conective Tissue Nevus: A New Clinical Presentation

Connective tissue nevi are benign hamartomatous lesions in which one or several of the components of the dermis (collagen, elastin, glicosaminoglycans) show predominance or depletion. Recently, de Feraudy et al broadened the spectrum of connective tissue nevus, describing fibroblastic connective tissue nevus (FCTN), which is characterized by proliferation of CD34(+) cells of fibroblastic and myofibroblastic lineage. Only solitary papules and nodules have been described. We present the first case of FCTN with multiple agminated lesions on the leg of an infant and the difficulties encountered in the differential diagnosis with dermatofibrosarcoma protuberans.

Advances in the clinicopathological and molecular classification of cutaneous mesenchymal neoplasms

In recent years, there have been several important refinements in the classification of cutaneous mesenchymal neoplasms, including the description of new tumour types, along with the identification of novel and recurrent molecular genetic findings. In addition to providing new insights into tumour biology, many of these advances have had significant clinical consequences with regard to diagnostics, management, and prognostication. Newly described entities include pseudomyogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour, and fibroblastic connective tissue naevus, which are reviewed in the context of the principal differential diagnoses and significant clinical implications. Genetic characterization of several soft tissue tumour types that occur in the skin has resulted in the identification of diagnostically useful markers: ALK gene rearrangement with corresponding ALK protein expression by immunohistochemistry in epithelioid fibrous histiocytoma; the WWTR1-CAMTA1 fusion gene with CAMTA1 protein expression in epithelioid haemangioendothelioma; MYC amplification and overexpression in radiation-associated angiosarcoma; and EWSR1 gene rearrangement in cutaneous myoepithelial tumours. Finally, the classification of intradermal smooth muscle tumours and unclassified/pleomorphic dermal sarcoma has been refined, resulting in both improved classification and improved prognostication. Many of the tumour types listed above are encountered not only by specialist dermatopathologists, but also by practising general surgical pathologists, and this review should therefore provide a widely applicable update on the histological and molecular classification of cutaneous mesenchymal neoplasms, along with the appropriate use of ancillary diagnostic tests, in particular immunohistochemistry, in the evaluation of such lesions and their histological mimics.

Fibrous Hamartoma of Infancy: A Firm Plaque Presenting with Hypertrichosis and Hyperhidrosis

Fibrous hamartoma of infancy (FHI) is a rare, benign, soft tissue tumor. The lesion's clinical resemblance to more aggressive soft tissue tumors of childhood makes histologic diagnosis paramount. We report a unique presentation of a FHI associated with localized hypertrichosis and hyperhidrosis.