A Tale of Two Tumors: A Collision Tumor of Atypical Fibroxanthoma and Basal Cell Carcinoma.

ABSTRACT: A collision tumor is an infrequent phenomenon characterized by the presence of 2 histologically distinct tumor types (either benign or malignant) occurring within the same specific anatomical site. We describe a rare case of co-occurrence of basal cell carcinoma and atypical fibroxanthoma presenting as a single lesion on the scalp in a 76-year-old man. The lesion was clinically suspicious for basal cell carcinoma and biopsied. Histologic examination showed 2 distinct tumors, one with basaloid cells and the other one with pleomorphic spindle cells colliding and growing together. Immunohistochemical stains were crucial in establishing the diagnosis. This presentation is exceedingly rare and requires additional evaluation for diagnosis.

Recurrent and metastatic cellular cutaneous fibrous histiocytoma: A case report and literature review.

Cutaneous fibrous histiocytoma (FH) is considered a benign dermal tumor. The cellular variant is rare and poorly documented. Besides presenting a high risk of local recurrence, it has a low but serious metastatic potential. We present a case of metastatic cellular FH and also review the literature on this tumor, given its unusual metastatic development. A 47-year-old male patient presented with a lesion in the anterior surface of the right thigh, which has been present since adolescence but had grown during last year. Anatomopathological evaluation revealed a cellular FH, and the lesion was completely removed. Six months later, tumor recurrence with multiple compartment muscle involvement and pulmonary metastasis were detected. Both lesions were completely resected and after 3 years of follow-up, the patient is asymptomatic and free of the disease. We conclude that FH should be carefully sampled to detect variants with high local recurrence rates or with some metastatic risk such as the cellular one. We recommend wide surgical resection and a close follow-up including chest x-rays or thorax computed tomography (CT) in all cellular FH cases with local recurrence.

A study of collagen refractility in dermatofibroma and dermatofibrosarcoma protuberans using diffractive microscopy.

BACKGROUND: Diffractive microscopy creates contrast within samples that are otherwise uniform under bright light. This technique can highlight subtle differences in refractive indices within birefringent samples containing varying amounts of mature collagen. Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) possess differences in their mature collagen content and, therefore, may be distinguishable using diffractive microscopy. METHODS: Two hundred forty-two DF and 85 DFSP hematoxylin-eosin (H&E)-stained specimens were analyzed using diffractive microscopy. Data regarding the distribution pattern and strength of refractility was recorded. RESULTS: DFSP was more frequently found to be focally, weakly, or non-refractile (82.9%; n = 68) under diffractive microscopy, while DF more often showed diffusely bright refractility (52.9%; n = 128). DFSP samples with diffuse refractility in portions of the lesion (17.1%; n = 14) also exhibited a unique checkerboard pattern distinct from that which was seen in DF samples. CONCLUSIONS: The absence of diffuse refractility was more closely associated with DFSP, as was the presence of a unique checkerboard diffraction pattern. Despite high sensitivity (Sn = 82.9%), absent refractility was not a specific test (Sp = 52.9%), with 47.1% (n = 114) of DF samples sharing this feature. The distinction between DF and DFSP is often diagnosed using H&E alone. In difficult cases, examination of collagen under diffractive microscopy may be useful in distinguishing DFSP from DF and provide an alternative cost-effective tool to immunohistochemical staining.

Epidermal inclusion cyst embedded in benign fibrous histiocytic lesion with prominent epithelioid morphology.

Benign fibrous histiocytoma also known as dermatofibroma is one of the common mesenchymal neoplasms. It commonly develops in young adult with female predominance and predilection for the extremities, particularly lower extremities. Implantation of epidermis in the dermis or subcutaneous tissues may lead to the formation of epidermal inclusion cyst, which is the most common type of epithelial cyst. Development of epidermal inclusion cyst within a benign fibrous histiocytoma is a rare occurrence. This is a unique case of two unrelated lesions.

Connexin 43 in Dermatofibroma and Dermatofibrosarcoma Protuberans: Diagnostic, Pathogenic, and Therapeutic Implications.

ABSTRACT: Connexins play a crucial role in the formation of gap junctions that connect cells to each other, as well as cells to the surrounding environment. In recent years, connexin 43 has been extensively studied in various human tumors. In this study, we conducted an immunohistochemical analysis to evaluate the expression of connexin in 16 dermatofibromas (DFs) and 13 dermatofibrosarcoma protuberans (DFSP). Connexin was diffusely expressed in the cytoplasm of all DFs with moderate or strong intensity, whereas all DFSPs showed negative staining. In addition to its diagnostic implications, the loss of Cx43 may elucidate the invasive capacity of DFSP and offer a potential avenue for future therapeutic interventions.

Multiple sclerosing hemangiomas mimicking hepatocellular carcinoma: A case report.

Hepatocellular carcinoma is a prevalent malignant tumor affecting the liver, and surgical resection and liver transplantation are the primary treatment options for early-stage HCC patients. However, the presence of benign hepatic tumors with similar imaging characteristics to HCC poses challenges in diagnosing and treating the disease, often resulting in misdiagnosis and inappropriate treatment. This case report presents a 52-year-old female patient who exhibited space-occupying liver lesions on abdominal CT and MRI scans. Based on pathological sections from other hospitals, liver malignancy was highly suspected, and hepatocellular tumor was diagnosed preoperatively. But the tumor markers of the patient were all within the normal range. After evaluating the overall condition of the patient, we finally chose the diagnosis and treatment of dissection and partial hepatectomy. Surprisingly, the final diagnosis of postoperative pathology was sclerosing hemangioma. The patient recovered well and was discharged 2 weeks later. Hepatic sclerosing hemangioma is an extremely rare disease that can be easily mistaken for malignant liver tumors due to absence of typical imaging presentations. The diagnosis also needs to be differentiated from other benign tumors, such as liver adenoma and liver abscess, according to the medical history, symptoms, and auxiliary examinations. Therefore, special attention should be given to the diagnosis and treatment of sclerosing hemangioma.

Benign fibrohistiocytic jaw lesions: a 48-year clinicopathologic analysis and review of the literature.

OBJECTIVE: Intra-osseous fibrohistiocytic lesions have long been reported in the literature; evidence suggests they represent a heterogeneous group of reactive and neoplastic processes. This study evaluated a series of gnathic fibrohistiocytic lesions to identify and categorize their clinical, radiographic and morphologic spectrum. STUDY DESIGN: A retrospective case search over 48 years was conducted for maxillary and mandibular intra-bony fibrohistiocytic lesions. Diagnoses were confirmed and demographic, radiographic, clinical and follow-up data was analyzed. RESULTS: Fifty cases met the inclusion criteria. Most cases (80%) were found in the second through fourth decades (mean, 29 years). The most common location (86%) was the posterior mandible. Radiographic presentations varied, but a few patterns emerged, including a distinctive mottled, honeycomb type with punctate lucencies. All cases demonstrated fibrous components admixed with variable histiocytes. Eight cases (16%) were histiocyte-rich with dominant sheets of xanthoma cells. Immunohistochemical staining revealed strong CD68 and CD163 expression, along with variable smooth muscle actin staining. The vast majority (92%) of cases were treated conservatively. Available follow-up showed lesional stability in 17 cases (average, 85 months) with 2 recurrences (24 months each) and no evidence of malignant transformation. CONCLUSIONS: This study is the largest to date of fibrohistiocytic gnathic lesions, revealing distinctive radiographic and histologic findings and characteristic clinical and immunophenotypic features. Available evidence suggests that most of these are indolent, slow-growing lesions amenable to conservative therapy.

A Novel Fusion Partner, SP100, Drives Nuclear Dot Localization of ALK in Epithelioid Fibrous Histiocytoma.

ABSTRACT: Epithelioid fibrous histiocytoma (EFH) is a distinctive benign cutaneous neoplasm composed of uniform epithelioid cells, often with binucleated cells. EFH are characterized by the presence of anaplastic lymphoma kinase ( ALK ) gene rearrangements with a variety of binding partners. These rearrangements result in the overexpression of ALK , which can be detected using immunohistochemistry. Cytoplasmic ALK expression is by far the most common pattern encountered. Here, we describe a case of EFH with a distinctive intranuclear dot-like ALK expression pattern. Subsequent next-generation DNA sequencing revealed a novel SP100::ALK gene fusion. Speckled protein-100 (SP100) is a constituent of nuclear dots, also known as promyelocytic leukemia bodies, which are still poorly understood membraneless subnuclear structures. Thus, this novel ALK fusion partner seems to explain this distinctive pattern of ALK localization. We examined ALK expression patterns in 11 other cases of EFH, but all showed typical cytoplasmic localization. This study expands the morphologic and molecular spectrum of EFH, provides a dramatic illustration of the ability of fusion partners to control protein localization, and implies that tumorigenic ALK signaling may occur at a variety of subcellular locations.

Treatment Options for Multinucleate Cell Angiohistiocytoma: A Case Series and Review of the Literature.

BACKGROUND: Multinucleate cell angiohistiocytoma (MCAH) is an unusual fibrohistiocytic proliferation in the dermis with vascular hyperplasia. Numerous clinicopathological studies of MCAH have been published, but little has been written in relation to treatment. OBJECTIVES: The aim of the present study is to review the therapeutical approaches for MCAH in the literature and to report the results of the different therapies followed at our institution. METHODS: A literature review was conducted including all MCAH published cases that followed any therapy. Search terms included "multinucleate cell angiohistiocytoma" or "MCAH" and "treatment" or "therapy". Also, all cases of MCAH treated at our institution from 2010 to 2020 are reported. RESULTS: The literature search revealed 16 cases of MCAH treated with any of the therapeutic options. At our institution, 9 patients have been treated of MCAH between 2010 and 2020. Over 75% of them were female, and the median age was 56 years (range 47-73). More than 50% had lesions on the dorsum of the hands. Surgical excision was indicated in 2 patients, ablative CO2 laser was used in 1 patient and the 6 remaining ones followed vascular-targeted therapies (PDL and IPL). A satisfactory cosmetic result was achieved in all of them. CONCLUSIONS: We propose PDL therapy as a first-line treatment for MCAH since it achieves satisfactory esthetic results, while being well-tolerated. Selecting those amenable patients according to morphologic characteristics may be useful to avoid unsuccessful therapies. In MCAH with predominant fibrous stroma, surgery or CO2 laser may be the best option.

Pulmonary artery angiomatoid fibrous histiocytoma mimicking pulmonary embolism.

A young man presented to the emergency department with pleuritic chest pain and shortness of breath. Of note, he recently went on a long-distance flight of about 9 hours. Given his recent long-distance travel and clinical symptoms, a pulmonary embolism was suspected. However, pathological examination of the excised pulmonary artery intraluminal mass demonstrated an angiomatoid fibrous histiocytoma. This case describes the clinicopathological and immunohistochemical features and molecular profile of a rare type of pulmonary artery tumour, a pulmonary artery angiomatoid fibrous histiocytoma.

[Plexiform fibrohistiocytic tumor]. / Plexiformer fibrohistiozytärer Tumor.

Plexiform fibrohistiocytic tumors are rare, low-to-moderate malignant soft tissue tumors that occur primarily in children and adolescents and are located on the upper extremity. The diagnosis must be made histologically. We report on a young woman who presented a growing, painless lesion on the cubital fossa. Histopathology as well as the standard of treatment are discussed.

Giant Hemosiderotic Adenodermatofibroma: A Case Report and Review of the Literature.

ABSTRACT: Adenodermatofibromas are an extremely rare subtype of dermatofibroma (DF) characterized by a dermal proliferation of spindle-shaped fibroblasts and histocytes, dilated glandular structures with apocrine secretion, and prominent vascular proliferation, with or without hemosiderotic features. We describe a recent extraordinary case of a hemosiderotic adenodermatofibroma in a 25-year-old female. We review histologic findings and theories behind etiology, as well as review the spectrum of clinical presentations for this lesion. We also discuss imaging findings that may make identification of these entities challenging.

Diagnostic utility of ERG immunostaining in dermatofibroma.

AIMS: Dermatofibroma/fibrous histiocytoma (DF/FH) is a common cutaneous mesenchymal neoplasm exhibiting benign biological behaviour. However, the immunohistochemical utility of erythroblast transformation-specific-related gene (ERG) for diagnosing DF remains unknown. The authors reviewed the immunohistochemical status of ERG in different subtypes of DF and in its differential diagnoses. METHODS: Overall, 97 cases of ordinary DF/FH, 6 cases of aneurysmal FH, 10 cases of cellular FH, 5 cases of angiomatoid FH, 2 cases of epithelioid FH, 64 cases of dermatofibrosarcoma protuberans (DFSP) and 52 cases of fibrous scar were retrieved. As the other histological types of cutaneous neoplasms, 6 cases of myxofibrosarcoma, 4 cases of undifferentiated pleomorphic sarcoma, 11 cases of atypical fibroxanthoma, 19 cases of malignant melanoma, 20 cases of nevocellular nevus, 20 cases of neurofibroma, 19 cases of schwannoma, 8 cases of angioleiomyoma and 1 case of pilar leiomyoma were included. RESULTS: Immunohistochemical positivity for ERG was demonstrated in 87 of 97 cases (89.6%) of ordinary DF/FH, 7 of 10 cases (70%) of cellular FH, 3 of 6 cases (50%) of aneurysmal FH, 1 of 5 cases (20%) of angiomatoid FH and 1 of 52 cases (0.1%) of fibrous scar. All cases of DFSP, epithelioid FH and other types of cutaneous neoplasms included in the current investigation were negative for ERG. The intensity of ERG immunohistochemical staining in spindle-shaped cells appeared weaker than that in endothelial cells. CONCLUSIONS: DF/FH was frequently positive for ERG immunostaining. ERG immunostaining may thus be useful to distinguish DF/FH from DFSP.

Dermoscopy of haemosiderotic/aneurysmal dermatofibroma: A morphological study of 110 cases.

BACKGROUND: Haemosiderotic and aneurysmal dermatofibromas are uncommon and frequently misdiagnosed lesions, which can be considered as different histopathological stages of the same tumour. A dermoscopic diagnosis testing accuracy has not been performed for these tumours to date. OBJECTIVES: To determine the diagnostic significance of dermoscopic structures and patterns associated with haemosiderotic/ aneurysmal dermatofibromas in a large series. METHODS: Dermoscopic images of histopathologically proven cases of 110 haemosiderotic/ aneurysmal dermatofibromas and 501 other tumours were collected. The frequency, sensitivity, specificity, positive predictive value and negative predictive value of the dermoscopic structures and patterns associated with these lesions were calculated. RESULTS: Haemosiderotic/ aneurysmal dermatofibromas are mostly symmetric lesions (86.5%), and a prominent homogeneous area was present in 100% of them. The presence of vascular structures was very common (86.4%), and dotted vessels were predominant (58.2%). Shiny white structures were seen in 85.5% of lesions, while a peripheral delicate pigment network was present in 69.1%. The most significant pattern was the one composed of a prominent homogeneous area and peripheral delicate pigment network, which showed a specificity of 100% with a relatively good sensitivity (69.1%). All the patterns containing a peripheral delicate pigment network showed very good specificities, positive predictive values and negative predictive values. Those patterns without a peripheral delicate pigment network showed the highest sensitivities, but they showed a significant overlap with other tumours, mainly with melanoma. CONCLUSIONS: Dermoscopy is helpful in improving the diagnostic accuracy of haemosiderotic/ aneurysmal dermatofibromas. However, there is a considerable dermoscopic overlap between these tumours and melanoma, specifically when the peripheral delicate pigment network is absent.

Dermatofibroma-like dermal non-neural granular cell tumor.

Non-neural granular cell tumor (NNGCT) is a rare tumor with uncertain lineage. It presents as an asymptomatic polypoid or plaque-like lesion, especially on trunk. Because the granular cells are usually strongly reactive with S-100 stain, conventional granular cell tumors (GCTs) are regarded as those of neural or Schwann cell origin. Unlike GCTs, NNGCT is not reactive for S-100 protein and is thought to derive elsewhere, presumably from mesenchymal stem cells. A 20-year-old woman presented with a solitary, dermatofibroma-like, brownish nodule on her right arm. The lesion developed 3 months before presentation without subjective symptoms. Histopathologic examination revealed a grenz zone overlying a poorly circumscribed tumor extending through the reticular dermis. The tumor cells were large and polygonal, and they had numerous eosinophilic small granules in the cytoplasm. Immunohistochemical stains were positive for CD68, vimentin, factor XIIIa, CD10, and cyclin D1. Stains for S-100 protein, neuron-specific enolase, and CD34 were negative. Based on these findings, the lesion was diagnosed as dermal NNGCT.

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.

Multiple dermatofibromas, associated clinical and histological characteristics: A systematic review.

Multiple dermatofibromas (DFs) are rare benign fibrohistiocytic lesions characterized by asymptomatic hyperpigmented nodules. Several diseases, like systemic lupus erythematosus (SLE) and human immunodeficiency virus (HIV) infection, are found to be associated with multiple DFs. Here, we designed a systematic review by an electronic search of PubMed and Embase databases to select case reports of multiple DFs (29 May 2021). From 2,145 initially found articles, 96 studies (106 cases) were included. We classified multiple DFs (>1 DF lesion) into four subtypes and separately investigated clinical characteristics of each one: multiple eruptive DFs (MEDFs) (n = 45), multiple (n = 41), multiple clustered DFs (MCDFs) (n = 18), and giant combined (n = 2). The patients' mean age was 38.3 ± 14.7 years. The majority were female (61.3 %). The lesions were commonly on the trunk and extremities (36.8 %). MEDFs (n = 36) had the most rapid disease onset (2.0 ± 6.6 years). Immunosuppression induced by either HIV (10.3 %) and hematologic malignancy (9.4 %) or immunosuppressive drugs (23.4 %) along with SLE (19.8 %) were the most observed associations. However, 66.7 % of the MCDF patients were otherwise healthy individuals. As for disease management, surgery and follow-up were the preferred options. Most of the cases showed neither resolution nor development of new lesions in follow-up.

Pigmented Multinucleate Cell Angiohistiocytoma: First Case.

ABSTRACT: Multinucleate cell angiohistiocytoma (MCAH) is a benign vascular and fibrohistiocytic (probably reactive) proliferation with peculiar multinucleate cells which most authors interpret as degenerated macrophages. Several clinical variants of MCAH have been described, some of them with brownish-appearing lesions clinically. However, no histologically identified pigment has been described in the cytoplasm of the multinucleate cells so far. We present a pigmented MCAH with cytoplasmic brownish pigment, which was positive with a Masson-Fontana stain and negative with an iron stain, consistent with melanin, in a 33-year-old woman with multiple papules and plaques on the right elbow, right jawline, and left flank.

Epithelioid fibrous histiocytoma: three diagnostically challenging cases with novel ALK gene fusions, unusual storiform growth pattern, and a prominent spindled morphology.

Epithelioid fibrous histiocytoma (EFH) is a distinctive cutaneous neoplasm with a relatively variable morphological appearance. Recently, it has been shown that this tumor is molecularly characterized by ALK gene fusions. We report three EFHs with unusual histological presentation represented by a prominent/predominant spindle cell proliferation arranged in a variably storiform/whirling architectural pattern with or without stromal sclerosis. One of the cases closely resembled cellular fibrous histiocytoma. All three cases were immunohistochemically ALK-positive and were analyzed for ALK gene rearrangements using a next-generation sequencing-based assay (FusionPlex Sarcoma Kit, ArcherDx). Three novel fusions, namely AP3D1::ALK, COL1A::ALK, and LRRFIP2::ALK, were detected and further confirmed by FISH in all 3 cases and RT-PCR in 1 case. All patients were elderly (62-63 years) and presented with a solitary polypoid lesion on the extremities. The awareness of these morphological variants is important since it entertains a wide and slightly different differential diagnosis than conventional EFH. We also presented evidence that a clear separation of EFH from BFH in all cases may not be as straightforward as previously thought. The consistent ALK immunoexpression and the continually expanding scale of ALK gene rearrangements provide a useful tool to distinguish EFH from its histologic mimics.

Benign fibrous histiocytoma of the medial rectus muscle.

We report the case of a healthy 17-year-old girl who underwent surgery for excision of a painless, rapidly enlarging subconjunctival mass. The mass was found to be tightly adherent to the medial rectus muscle of the left eye, requiring extensive dissection. Histopathology revealed a mass of bland and foamy spindle cells in a storiform pattern that was positive for CD68, PGM1, and factor XIIIA and negative for S-100. The clinical and histopathologic findings are consistent with benign fibrous histiocytoma.