Dermatofibroma—A Critical Evaluation

Pediatric dermatofibromas: Truncal predominance in younger children

Pediatric dermatofibromas are considered rare in young children and have not been well characterized, often misdiagnosed clinically. We performed a retrospective case series of children younger than 18 years with histopathologically diagnosed dermatofibromas at our institutions and evaluated age at onset and diagnosis, sex, lesion location, and size, associated symptoms, change over time, and pre-biopsy diagnosis. Overall, dermatofibromas were most common on the back and chest (20/53; 38%), followed by the legs (15/53; 28%) and arms (12/53; 23%) with the most common pre-biopsy diagnosis of "cyst" (23/53; 43%), followed by dermatofibroma (16/53; 30%), and pilomatricoma (12/53; 23%). Our study reinforces previous findings of truncal predominance of pediatric dermatofibromas, different from adults.

Keloidal dermatofibroma: Clinicopathological comparison of 52 cases with a series of 2077 other dermatofibromas

Dermatofibroma is a common benign skin lesion with a contested etiology: some believe it is a neoplasm while others propose minor injuries initiate it. Many dermatofibroma variants have been described, including keloidal dermatofibroma, which is unusual by bearing keloidal collagen. Keloidal dermatofibroma was first described in 1998 and only 15 cases have been reported. Since keloids are driven by skin injuries, the existence of keloidal dermatofibroma has been suggested to support the injury hypothesis of dermatofibroma etiology. To better understand keloidal dermatofibroma characteristics and gain clues regarding dermatofibroma etiology, consecutive keloidal dermatofibroma cases (n = 52) and dermatofibroma without keloidal collagen (n = 2077) that were histopathologically diagnosed in 2016-2019 were identified from the records of a Japanese dermatopathology laboratory and compared in terms of demographic, clinical, and histopathological characteristics by univariate analyses. Compared to other dermatofibromas, keloidal dermatofibromas occurred more frequently on the forearm and hand (P < 0.0001 and 0.0019), especially the wrist dorsum, and in the superficial skin layer (P < 0.0001). Keloidal dermatofibromas also demonstrated more cellularity and hemorrhage (both P < 0.0001). Correlation analyses between keloidal collagen amount and keloidal dermatofibroma size (a proxy of time-since-onset) did not support the notion that keloidal collagen deposition and keloidal dermatofibroma formation are triggered simultaneously. Recent injury, as indicated by fresh hemorrhage, was equally common in putatively older and younger keloidal dermatofibromas. Thus, keloidal collagen in keloidal dermatofibromas could be due to injury to preexisting dermatofibromas, which suggests that the keloidal dermatofibroma entity does not prove the injury hypothesis. Commonalities between keloids and keloidal dermatofibromas suggest a link between genetics, provocative events that induce myofibroblast differentiation, and keloidal collagen production.

Clinicopathologic Features of Facial Dermatofibromas, a Cohort Study, and a Systematic Review of Literature

BACKGROUND

Dermatofibromas are common skin tumors that typically occur on the extremities and trunk and demonstrate benign behavior, frequent recurrences, and very rare metastasis. Facial dermatofibromas are rare and not well studied . We analyzed clinicopathologic features of facial dermatofibromas.

DESIGN

Considering the rarity of the condition, we conducted a cohort study and a systematic review. We queried medical records of a single tertiary care center for dermatofibromas from January 1, 2000, to July 1, 2021. A systematic review of multiple databases was conducted through October 27, 2021, to include studies reporting facial dermatofibromas. Random-effects meta-analysis was used to estimate pooled odds ratio and proportions with associated 95% confidence interval (CI).

RESULTS

The cohort study identified 2858 cases of dermatofibromas, of which, 23 cases from 18 patients were on the face (1%). The mean age was 52.7 ± 17.8 years. Fifty-six percent of the cases were women. The most common location was the forehead (6 cases). The mean follow-up was 54 months. Forty-four percent of the cases had subcutaneous involvement, and 39% were the cellular type. Margins were positive in 89% of the cases, recurrence rate was 22%, and no metastases were observed. The systematic review included 10 studies (119 patients). Meta-analyses showed that facial dermatofibromas were 2% of all dermatofibromas (95% CI: 1%-3%). The local recurrence rate was 14% (95% CI: 6%-26%). Facial dermatofibromas with subcutaneous involvement were more likely to recur [odds ratio 4.53 (95% CI: 1.12-18.24)]. Before histopathologic examination, clinical differential diagnosis included dermatofibromas in only 9% of the cases (95% CI: 2%-19%).

CONCLUSION

Facial dermatofibromas are rare and are difficult to fully excise. Cellular type and subcutaneous or muscular involvement are common in these cases and tend to have higher local recurrence rate than other nonfacial dermatofibromas. Wider excisions might be necessary for complete excision.

Cutaneous Fibrous Histiocytomas, Ossifying-Variant with Osteoclast-like Giant Cells and Granular Cell-Variant: A Series of Two Unusual Cases with Emphasis on the Differential Diagnosis

The ossifying variant and the granular cell variant are rare subtypes of cutaneous fibrous histiocytoma (CFH), characterized by islands of mature metaplastic bone tissue rimmed by multinucleated osteoclast-like giant cells and by large-sized cells with granular cytoplasm and mildly hyperchromatic nuclei with inconspicuous nucleoli, respectively. We herein present two cases of these unusual CFH variants in a 37-year-old woman and in a 38-year-old man, respectively. The main differential diagnoses, including both benign and malignant lesions, are also discussed.

Role of Wnt signaling in dermatofibroma induction phenomenon

BACKGROUND

Dermatofibroma (DF) is a common benign skin neoplasm. Induction above DF lesions, including follicular unit induction, is a frequently observed phenomenon. Wnt signaling is known to be critical in hair follicle morphogenesis. Our study assesses the role of Wnt signaling in DF induction by evaluating intracellular localization of β-catenin in various types of DF induction.

METHODS

Archived tissue collected between 1 October 1980 and 1 October 2013 was stained per protocol using hematoxylin and eosin and anti-β-catenin monoclonal antibody. Specimens were grouped into categories based on the presence or absence and type of induction. All specimens were scored for nuclear β-catenin localization.

RESULTS

Of 62 specimens, 42 (68%) showed induction while 20 (32%) showed none. Nuclear β-catenin staining was detected in 23 (55%) of the induction and in none of the no-induction specimens (P-value < 0.001). Types of induction included: 15 (24%) follicular induction, 31 (50%) acanthosis, and 4 (6%) sebaceous induction. For follicular induction, 13 (87%) showed positive nuclear β-catenin staining compared to 11 (35%) for acanthosis and 1 (25%) for sebaceous induction (P-value = 0.002).

CONCLUSION

Our findings support the hypothesis that DFs promote an ectopic activation of Wnt pathway signaling in follicular induction phenomenon.

Perineural Invasion as a Clue to Malignant Behavior in a Dermatofibroma

Dermatofibroma (DF) represents one of the most common mesenchymal proliferations of the skin. Their recurrence rate, even when incompletely excised, is very low, whereas the atypical, aneurysmal, and cellular variants have recurrence rates of up to 20% each. Extraordinary rare malignant lesions with metastases to lymph nodes and/or lung have been described. We report a 64-year-old woman with a long history (years) of a skin lesion on her right arm that became painful during the last months. Histologically, it consisted of a conventional cellular DF in which perineural invasion was present. Subsequently, the lesion showed a clinically aggressive course with recurrences, sarcomatous transformation, and pulmonary metastases. Given that no predictive morphological features have been identified to separate classical benign DF from rare metastasizing forms, perineural invasion in an otherwise conventional DF could be a histopathologic clue for an adverse prognosis and should provoke a closer clinical follow-up.

Distinguishing a Rare Variant of Lipidized Dermatofibroma from Nonlipidized Dermatofibromas in a Patient with Hypothyroidism and Alopecia Areata

Introduction. Lipidized dermatofibromas represent rare and often underrecognized variants of dermatofibromas. Histologically, dermatofibromas are composed of fibroblast-like spindle cells, foam cells, giant cells, siderophages, lymphocytes, capillaries, collagen fibers, and hyaline dermal collagen fibers. Lipidized dermatofibromas are characterized by numerous foam cells, Touton giant cells, and hyalinized wiry collagen in the stroma. Case report. We present a case of a 31-year-old woman with a history of hypothyroidism and alopecia areata, presenting with an enlarging 8 mm, firm erythematous nodule on her upper-mid back. Biopsy examination showed a cellular proliferation of spindle cells with peripheral collagen trapping and cholesterol clefts with associated foam cells and sclerosis, staining weakly positive for Factor XIIIa and negative for CD34. The diagnosis of a benign lipidized dermatofibroma was rendered. Conclusion. Lipidized dermatofibromas are rare histologic variants of dermatofibromas, biologically indolent, and should be distinguished from other cutaneous foamy histiocytic lesions, particularly xanthomas, which may alter patient management.

Compartmentalized Epidermal Activation of β-Catenin Differentially Affects Lineage Reprogramming and Underlies Tumor Heterogeneity

Wnt/β-catenin activation in adult epidermis can induce new hair follicle formation and tumor development. We used lineage tracing to uncover the relative contribution of different stem cell populations. LGR6(+) and LRIG1(+) stem cells contributed to ectopic hair follicles formed in the sebaceous gland upon β-catenin activation, whereas LGR5(+) cells did not. Lgr6, but not Lrig1 or Lgr5, was expressed in a subpopulation of interfollicular epidermal cells that were competent to form new hair follicles. Oncogenic β-catenin expression in LGR5(+) cells led to formation of pilomatricomas, while LRIG1(+) cells formed trichoadenomas and LGR6(+) cells formed dermatofibromas. Tumor formation was always accompanied by a local increase in dermal fibroblast density and transient extracellular matrix remodeling. However, each tumor had a distinct stromal signature in terms of immune cell infiltrate and expression of CD26 and CD44. We conclude that compartmentalization of epidermal stem cells underlies different responses to β-catenin and skin tumor heterogeneity.

Increased FDG activity in a dermatofibroma in esophageal cancer patient

PET using the radiotracer (18)F-FDG is used for staging patients with esophageal cancer. Nonmalignant conditions, mainly inflammation and some benign tumors, however, can cloud the clinical picture by taking up FDG and producing a false-positive result. We report the case of a 46 year-old man with squamous cell carcinoma of the thoracic esophagus who underwent combined PET/CT and had false-positive uptake in a chest wall dermatofibroma. Dermatofibroma is a benign skin lesion with a characteristic large presence of fibroblasts and macrophages. Macrophage uptake of FDG is likely responsible for the false-positive result on PET/CT.

Nonepithelial skin tumors with multinucleated giant cells

Recognition of the different types of multinucleated giant cells in neoplastic and pseudotumoral lesions of the skin may be helpful in the differential diagnosis of these tumors. In this review, we will analyze the different types of multinucleated giant cells that can be found in nonepithelial cutaneous tumors and, more importantly, the clinicopathological context in which they are found. Touton giant cells are typically present in juvenile xanthogranuloma, necrobiotic xanthogranuloma, and some subtypes of xanthomas. Giant cells with a ground glass appearance are typically present in the solitary reticulohistiocytoma and multicentric reticulohistiocytosis. Osteoclast-like cells are found in giant cell tumors (GCT) of soft parts, plexiform fibrohistiocytic tumor, and atypical fibroxanthoma. Floret-like cells are present in giant cell fibroblastoma, pleomorphic lipoma, multinucleate cell angiohistiocytoma, and giant cell collagenoma.

Atypical fibroxanthoma

Atypical fibroxanthoma (AFX) is a rare neoplastic disease of the skin. Since the term was coined in the early 1960s, the disease has been viewed in many ways. For a long time AFX was regarded as a superficial variant of malignant fibrous histiocytoma (MFH). When the concept of MFH was re-evaluated and the term "undifferentiated pleomorphic sarcoma" (UPS) introduced, the controversy about the nature of AFX increased. The following review aims at providing an understanding of the present status of diagnosis and therapy of AFX based on the historical context and current data.

Fibrohistiocytic tumors and related neoplasms in children and adolescents

Fibrohistiocytic tumors (FHTs) in children and adolescents range from the benign fibrous histiocytoma, or dermatofibroma, to a variety of intermediate and malignant neoplasms, such as dermatofibrosarcoma protruberans and high-grade undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). Those tumors as a group are comprised of fibroblasts, myofibroblasts, and histiocytes-dendritic cells with a variably prominent inflammatory infiltrate consisting of lymphocytes and eosinophils. Dendritic cells are also a major constituent of another group of neoplasms that include Langerhans cell histiocytosis, follicular and interdigitating cell sarcomas, and juvenile xanthogranuloma. These latter tumors are considered in this discussion for the sake of differential diagnosis and their possible histogenetic relationship to FHTs. Recent studies have suggested that the relationship between the fibroblast and histiocyte in the FHTs may reflect the intrinsic capacity to transdifferentiate from one to the other morphologic and functional state. The so-called "facultative fibroblast," as a cell with fibroblastic and histiocytic properties, was discussed in the context of the fibrous xanthoma 50 years ago. Possibly the entire histogenetic concept of FHTs should be reconsidered in light of current studies.

Collapsing angiokeloidal dermatofibroma

A heterogeneous group of benign fibrohistiocytic lesions has been assembled under the umbrella term, dermatofibroma. These lesions share a morphology of bland spindled cells encompassed by and intercalating through thick dermal collagen; unique variants have been described based on secondary histologic features, some of which include aneurysmal, myxoid, lipidized, signet ring, angiomatous, and keloidal. Here, we present a distinct dermatofibroma variant henceforth known as collapsing angiokeloidal dermatofibroma identified in 2 patients with slowly growing nodules of the buttock and the arm. Microscopically, the lesions have a characteristic dermatofibroma appearance but are accompanied by unusual diffuse small caliber vessels whose walls are collapsed by a thick, eosinophilic, keloid-like substance. The eosinophilic material resembles the adjacent dermal collagen; however, it does not stain for type-4 collagen or type-1 procollagen, amyloid, or glycogen. Although the exact composition of the keloidal material remains ambiguous, the architectural novelty of collapsing angiokeloidal dermatofibroma serves to further expand the morphologic spectrum of benign fibrous histiocytomas, although highlighting the difficulty in distinguishing between it and similar lesions.

Gender aspects in skin diseases

Gender differences in medicine have been recognized in anatomy, physiology, as well as in epidemiology and manifestations of various diseases. With respect to skin disorders, males are generally more commonly afflicted with infectious diseases while women are more susceptible to psychosomatic problems, pigmentary disorders, certain hair diseases, and particularly autoimmune as well as allergic diseases. Significantly, more female sex-associated dermatoses can be identified than the male sex-associated dermatoses. Dermatoses in the genital area differ between men and women. Gender differences also exist in the occurrence and prognosis of certain skin malignancies. The mechanisms underlying gender differences in skin diseases remain largely unknown. Differences in the skin structure and physiology, effect of sex hormones, ethnic background, sociocultural behaviour and environmental factors may interact to exert the influences. A better understanding of gender differences in human health and diseases will allow the development of novel concepts for prevention, diagnosis and therapy of skin diseases.

Rapidly evolving giant dermatofibroma

Dermatofibroma, also known as “fibrous histiocytoma”, is a benign dermal or subcutaneous poorly circumscribed proliferation of spindle-shaped fibroblasts and macrophages in the dermis. Although it is commonly present as a brownish nodule the legs of females, it may also arise on the upper extremities, trunk, and rarely on the head. The exact pathogenesis is unclear. However, it is widely believed that the originating insult to the dermis is a folliculitis, an arthropod bite, or an unspecified initial inflammatory condition. Giant dermatofibromas of greater than 5 cm in diameter are rare, with only 22 cases reported in the literature. We present a case of a rapidly evolving pedunculated mass in the groin of a male patient. Histological examination confirmed this to be a giant dermatofibroma. Though this specimen cannot is not confirmed as such, the cellular subtype is sometimes present as a larger lesion with anecdotal reports of local recurrence and distant metastases. The clinical and radiological features which were somewhat suspicious of malignancy are considered in the context of the definitive pathological diagnosis of a benign lesion.

Amyloid light chain deposition associated with dermatofibroma: serendipity or association?

Primary cutaneous amyloidosis, also known as nodular amyloidosis, is defined as deposition of amyloid light chain in the skin in the absence of a systemic cause of amyloidosis. Such amyloid is produced by a localized aggregate of clonal plasma cells. In contrast, secondary cutaneous amyloidosis is related to lesions such as squamous cell carcinoma, Bowen disease, basal cell carcinoma, and discoid lupus erythematosus, and has been shown in most cases to be derived from keratin epithelial elements. Herein, we present a unique case of nodular amyloidosis occurring in association with a cellular dermatofibroma.

Multiple clustered dermatofibroma with overlying sebaceous hyperplasia

Multiple clustered dermatofibroma is a very rare clinical variant of the dermatofibroma, and sebaceous differentiation overlying dermatofibromas is also unusual. We report the first case of a multiple clustered dermatofibroma with overlying sebaceous hyperplasia.

Phenotypic characterization of human keratinocytes in coculture reveals differential effects of fibroblasts from benign fibrous histiocytoma (dermatofibroma) as compared to cells from its malignant form and to normal fibroblasts

BACKGROUND

Benign and malignant fibrous histiocytoma present with a considerable difference concerning cellular organization in their vicinity.

OBJECTIVE

Normally appearing epithelium covers the malignant form in contrast to hyperplastic epidermis for benign tumors. It is an open question as to whether the tumor-associated fibroblasts are capable to affect phenotypic features of normal keratinocytes, prompting this comparative analysis.

METHODS

Fibroblasts were isolated from benign and malignant fibrous histiocytomas, respectively, and also from normal dermis. The resulting cell populations were thoroughly characterized immunocytochemically using a large panel of antibodies. The three fibroblast preparations were cocultured with normal interfollicular keratinocytes. Their phenotype was characterized for distinct properties including differentiation and proliferation.

RESULTS

Fibroblasts prepared from both tumor types were phenotypically practically identical with normal dermal fibroblasts. Their activities on keratinocytes were different. Cells prepared from benign fibrous histiocytoma were capable to effect strong expression of keratin 19 and production of a galectin-1-rich extracellular matrix. Fibroblasts isolated from malignant fibrous histiocytoma led to a phenotype very similar to that when keratinocytes were cocultured with normal dermal fibroblasts.

CONCLUSION

Fibroblasts prepared from benign fibrous histiocytoma were biologically active on keratinocytes in a particular manner. Our results on fibroblast activity are suggested to be relevant for morphologic differences observed in vivo between normal epidermis and epidermis adjacent to the studied tumor types.

Myofibroblastic Dermatofibroma: An Unusual Variant / Miofibroblastni Dermatofibrom: Neuobičajena Varijacija

Myofibroblastic dermatofibroma (MFD) is an unusual neoplasm characterized by a predominance of myofibroblastic differentiation. It is extremely rare and it is not well described. Expressions of smooth muscle actin, CD34, S-100, desmin, CD31, and Factor XIIIa were evaluated along with hematoxylin-eosin and trichrome staining of fixed tissue specimens from a fibrohistiocytic neoplasm. The neoplasm demonstrated a storiform pattern characteristic of fibrohistiocytic origin. It was strongly and diffusely positive for smooth muscle actin and vimentin, and negative for all other stains performed. A trichrome stain showed the entire tumor to be blue, demonstrating the collagenous and fibrous tissue to a marked degree. MFD is a distinct variant of dermatofibroma characterized by a predominance of myofibroblastic differentiation.

Multiple eruptive myxoid dermatofibromas: report of first case and review of literature

Multiple eruptive dermatofibromas are a rare presentation of dermatofibroma which are frequently associated with underlying diseases such as human immunodeficiency virus infection or lupus erythematosus. Eruptive dermatofibromas generally present a characteristic histology with a poorly circumscribed lesion showing hyperplasia of the epidermis, prominent bundles of collagen and a diffuse proliferation of fibrocytes. We report an unusual case of multiple eruptive dermatofibromas showing massive depositions of mucin within the dermis. A 20-year-old woman presented with nearly 100 red to yellowish papules and nodules distributed symmetrically all over the integument which developed over a period of 9 years. Comprehensive clinical and laboratory diagnostics showed no signs indicating any underlying disease. To our knowledge this is the first report of multiple eruptive myxoid dermatofibromas. We consider this case to be a unique presentation of multiple eruptive dermatofibroma showing massive deposition of mucin.