Cutaneous soft tissue tumors: how do we make sense of fibrous and "fibrohistiocytic" tumors with confusing names and similar appearances?

In the 2018 World Health Organization Classification of Skin Tumors, a wide range of predominantly benign mesenchymal neoplasms are included in the fibroblastic, myofibroblastic, and "fibrohistiocytic" categories. By far the most common of these tumors is dermatofibroma (fibrous histiocytoma). There are many histologic variants of dermatofibroma, some of which (cellular, aneurysmal, and atypical) are associated with a higher risk of local recurrence; these variants may be mistaken for more aggressive tumor types, including sarcomas. Furthermore, distinguishing among the fibrous and "fibrohistiocytic" tumors can be a diagnostic challenge, given their sometimes-similar histologic appearances and confusing nomenclature. Immunohistochemistry and molecular genetic assays play a relatively limited role in the diagnosis of these tumor types, with notable exceptions (i.e., epithelioid fibrous histiocytoma and dermatofibrosarcoma protuberans). Proper recognition of dermatofibrosarcoma protuberans is critical, since this tumor type is associated with locally aggressive behavior; transformation to the fibrosarcomatous variant brings metastatic potential. In recent years, understanding of the molecular pathogenetic basis for cutaneous mesenchymal neoplasms has increased dramatically, with the discovery of gene rearrangements in some of these tumor types. In this review, the histologic features of the most common fibrous and "fibrohistiocytic" cutaneous mesenchymal neoplasms will be discussed, as well as recently identified molecular genetic alterations.

Hemangioma esclerosante mandibular em Paralichthys orbignyanus: relato de caso / Sclerosing hemangioma mandibular in Paralichthys orbignyanus: case report

Neste trabalho, descreveu-se o primeiro caso de hemangioma esclerosante registrado em um exemplar adulto do linguado Paralichthys orbignyanus. Produzido a partir de reprodução artificial, o peixe em questão tinha aproximadamente 10 anos de idade e fazia parte de um plantel de reprodutores. Ao ser retirado do tanque, notou-se a presença de lesão mandibular com escoriações e focos hemorrágicos. Amostras do tumor foram coletadas da mandíbula para análise histopatológica. Microscopicamente foi observada uma proliferação de numerosos vasos sanguíneos rodeados por um estroma conectivo denso. A etiologia dessa neoplasia é desconhecida, mas o fato de o exemplar ter permanecido por muitos anos em cativeiro pode ter contribuído para o surgimento desse tipo de lesão, devido aos choques mecânicos contra a parede do tanque que acontecem esporadicamente.(AU)

In this study, we described the first case of sclerosing haemangioma in an adult Brazilian flounder Paralichthys orbignyanus. Produced by artificial reproduction, the fish was approximately 10 years old and was maintained at a breeding stock. When removed from the tank, mandibular lesion with excoriations and hemorrhagic foci were noted. Tumor samples were collected from the mandible for histopathological analysis. Proliferation of numerous blood vessels surrounded by dense connective stroma was observed microscopically. The etiology of this neoplasia is unknown, but the fact that the specimen remained in captivity for many years, may have contributed to the appearance of this type of lesion, due to sporadic mechanical shocks to the tank wall.(AU)

Clinical and histological patterns of dermatofibroma without gross skin surface change: A comparative study with conventional dermatofibroma.

BACKGROUND: Dermatofibroma sometimes clinically presents as a nodular lesion without gross skin surface change. Clinicopathologic features of this variant of dermatofibroma have not been evaluated. AIMS: To assess clinicopathologic features of dermatofibroma presenting as a subcutaneous nodule. METHODS: This study reviewed the clinical and histological features of 42 cases of subcutaneous dermatofibromas and compared them with 95 cases of conventional dermatofibroma. RESULTS: Dermatofibroma without gross skin surface change was associated with a shorter pre-diagnosis duration than conventional dermatofibroma. Increase in size during the pre-diagnosis period was significantly more frequent in the conventional type. In addition, these dermatofibromas were more likely than the conventional type to occur in the head and neck region. Although tumor depth was deeper than in the conventional type, less than half of the dermatofibromas without gross skin surface change were found histologically to be "subcutaneous" or "deep-penetrating dermatofibroma". Subcutaneous extension was more frequent in these dermatofibromas while focal stromal hyalinization and hemosiderin deposits were more common in the conventional type. LIMITATIONS: This study is a retrospective, single center design. CONCLUSION: The present study suggests that dermatofibroma without gross skin surface change is a variant type with distinct clinical and histological features that distinguish them from conventional dermatofibroma.

[Fibrohistiocytic tumors of the skin: a heterogeneous group of superficially located mesenchymal neoplasms]. / Fibrohistiozytäre Tumoren der Haut: Eine heterogene Gruppe oberflächlich lokalisierter mesenchymaler Neoplasien.

So-called fibrohistiocytic tumors of the skin comprise a heterogeneous spectrum of superficially located neoplasms that often show fibroblastic and/or myofibroblastic differentiation. In this review clinicopathologically important variants of dermatofibroma and dermatofibrosarcoma protuberans and their differential diagnoses are discussed in detail. In addition, the clinicopathological features of atypical fibroxanthoma, angiomatoid fibrous histiocytoma, plexiform fibrohistiocytic tumors and pleomorphic dermal sarcoma are presented. Entities that have to be considered in the differential diagnosis are also mentioned.

[Endocrine mucin-producing sweat gland carcinoma. three case reports with a brief review of the literature]. / Endokrines muzinproduzierendes Schweißdrüsenkarzinom. Drei Fallberichte mit kurzer Literaturübersicht.

Endocrine mucin-producing sweat gland carcinoma (EMPS) is a rare low-grade sweat gland carcinoma with an infiltrating growth pattern. It occurs mostly in women and shows a predilection for the periorbital region. Histopathologically, the tumor shows analogous features to endocrine ductal carcinoma/solid papillary carcinoma of the breast and shares some clinical and morphological similarities with primary mucinous carcinoma of the skin. The tumor is characterized by large monomorphous epithelial cells with little nuclear pleomorphism and only a few mitotic figures. The solid cystic tumor shows mucin-filled small cystic spaces, cribriform areas and expresses the neuroendocrine markers synaptophysin, chromogranin and neuron-specific enolase with varying staining intensities. The tumor cells are also positive for estrogen and progesterone receptors. We present three cases of this rare tumor with typical clinical, histopathological and immunohistochemical findings, give a short summary of the literature and discuss the most relevant differential diagnoses.

Recently characterized soft tissue tumors that bring biologic insight.

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

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.

Experiencia de linfomas cutáneos entre enero de 1995 y abril de 2008 en el Instituto Nacional de Cancerología / Experience with cutaneous lymphomas between January 1995 and April 2008 at the National Cancer Institute

Objetivos: Describir los diferentes linfomas cutáneos conforme a la clasificación WHO- EORTC, observados en el Instituto Nacional de Cancerología (INC) entre el 1° de enero de 1995 y abril de 2008. Métodos: Estudio retrospectivo, descriptivo, donde se incluyó a los pacientes con diagnóstico de linfoma cutáneo en el INC desde enero de 1995 hasta abril de 2008. La ubicación de las historias clínicas se realizó utilizando la base de datos del Departamento de Patología. El análisis estadístico se realizó mediante el programa Epi info 2008. Resultados: Se revisaron 252 historias y se incluyó a 160 pacientes en el estudio: 139 linfomas T (87%) y 21 linfomas B (13%). El linfoma más común fue la micosis fungoide (63% de los casos). Dentro de las variantes descritas de micosis fungoide (MF) llamó la atención la frecuencia de MF hipopigmentadas (13%). El grupo de enfermedades linfoproliferativas CD30+ fue el segundo en frecuencia dentro de los linfomas T. En el grupo de linfomas B los linfomas indolentes de excelente pronóstico se presentaron en un 5% de los casos. Conclusiones: Los linfomas cutáneos primarios son tumores raros. Predominan los linfomas de células T sobre los B. La mayoría de los casos son linfomas de bajo grado, y deben tratarse con terapias dirigidas a la piel. Dentro de cada categoría existen linfomas que van a progresar y comprometer órganos internos.

Objectives: To describe different cutaneous lymphomas in accordance with WHO-EORTC classification under observation at the National Cancer Institute (NCI) between January 1, 1995 and April, 2008. Methods: A descriptive, retrospective study was carried out which included patients diagnosed with cutaneous lymphoma at the NCI from January 1995 until April 2008. Clinical cases were taken from Pathology Department data base. Statistical analysis was performed with Epi 2008 info program. Results: A total of 252 case histories were reviewed, and 160 patients were included in the study: 139 T-cell lymphomas (87%) and 21 B-cell lymphomas (13%). The most common (63% of cases) was mycosis fungoides (MF). Among the variations of MF described, the frequency of hypopigmented MF (13%) stood out. The lymphoproliferative CD30+ disease group was the second most frequent among T-cell lymphomas. In the B-cell lymphoma group, the indolent lymphomas with excellent prognosis made up 5% of cases. Conclusions: Primary cutaneous lymphomas are rare tumors. T-cell lymphomas predominate over B-cell. Most cases are low grade lymphomas and should be treated with skin therapies. Within each category, lymphomas exist that will progress and compromise internal organs.

An unclassifiable cellular myofibroblastic proliferation with an unusual clinical presentation.

We present a case of a 50-year-old man with unusual extensive linear lesions on the right leg that had been present from the age of 2 years. As a child he had been treated with oral steroids under a working diagnosis of linear scleroderma. He went on to undergo multiple operations and skin-grafting procedures under the care of the plastic surgeons and presented to the dermatology department in 2004 because of itchy, scaly and painful lesions extending from the original area. Multiple biopsies had been taken, all showing similar histopathological features of a poorly differentiated dermal lesion composed of fibrohistiocytic cells arranged in a whorled pattern, similar to that seen in dermatofibroma. There was positive staining with vimentin and SMA, and negative staining with caldesmon, D33, CD34, S100 and factor 13a, indicating that the cell of origin was a myofibroblast. Clinically this extensive lesion does not fit the characteristics of a dermatofibroma. It also does not fit readily into any previously described fibrous tissue tumour condition, and, to our knowledge, is a unique case. The patient remains under close clinical observation given that there is no way of predicting the long-term prognosis, but to date no suspicious features have been seen.

Dermatofibroma gigante: descripción de un caso y revisión de la literatura / Giant dermatofibroma: case report and review of the literature

El dermatofibroma es una lesión muy frecuente que suele aparecer como un nódulo en dermis de lento crecimiento que afecta de forma predominante a las mujeres en los miembros inferiores. Se han descrito diferentes variedades clínicas. El dermatofibroma gigante se ha definido como una variante poco común de dermatofibroma de más de 5 cm que presenta las características histológicas típicas y un comportamiento biológico benigno. Presentamos el caso de un varón de 52 años que presentó un dermatofibroma gigante de 6 cm de diámetro en el hombro derecho y hacemos una revisión de los pocos casos de esta variedad descritos en la literatura

Dermatofibroma is a very frequent lesion that usually appears as a slowly growing nodule in the dermis, and preferentially involves the lower extremities of women. Several clinical variants have been described. Giant dermatofibroma has been defined as a rare variant of dermatofibroma measuring more than 5 cm that presents typical histological features and a benign biological behavior. We report the case of a 52-year-old man that presented a giant dermatofibroma with a diameter of 6 cm in the right shoulder and we review the few cases of this variant that have been described in the literature

Pseudoangiomatosis eruptiva / Eruptive pseudoangiomatosis

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World Health Organization classification of bone and soft tissue tumors: modifications and implications for radiologists.

The working group of the World Health Organization (WHO) for classification of tumors of soft tissue and bone met in 2002. The consensus of this conference led to modifications in the nomenclature primarily for soft tissue neoplasm, leaving osseous tumors largely unaltered. The most significant changes in nomenclature involved the group of fibrous and lipomatous malignancies. This article reviews the modifications of this nomenclature and the justification for these changes. The WHO suggested replacement of the term MALIGNANT FIBROUS HISTIOCYTOMA (MFH) with undifferentiated high-grade pleomorphic sarcoma and combining myxoid and round cell liposarcoma under the umbrella of myxoid liposarcoma. The imaging appearances of the fibrous and lipomatous malignancies is reviewed and emphasized in this article. It is important for radiologists involved in evaluation of these lesions to have an understanding of the current nomenclature. This allows improved uniformity in our discussions with pathologists and orthopedic oncologists in our team approach in the diagnosis and treatment of these patients.

[Fibrohistiocytic skin tumors]. / Fibrohistiozytäre Tumoren der Haut.

The fibrohistiocytic tumors of the skin are a heterogeneous group of dermal/subcutaneous mesenchymal neoplasms which show fibroblastic, myofibroblastic and histiocytic (macrophage-like) differentiation, often one beside the other in the same tumor. "Fibrohistiocytic" means in this context the morphologic similarity of the cells with fibroblasts and histiocytes. The WHO classification of 2005 includes the following entities as fibrohistiocytic tumors of the skin: BENIGN: 1. Fibrous histiocytoma (FH)/(synonymous: Dermatofibroma. Variants of FH: 1a. cellular fibrous histiocytoma, 1b. atypical (pseudosarcomatous) fibrous histiocytoma, 1c. aneurysmatic fibrous histiocytoma, 1d. epithelioid fibrous histiocytoma; 2. dermatomyofibroma; 3. (juvenile) xanthogranuloma. INTERMEDIATE: 4. plexiform fibrohistiocytic tumor; 5. dermatofibrosarcoma protuberans; 6. atypical Fibroxanthoma. MALIGNANT: 7. malignant fibrous histiocytoma. All these entities are reviewed in this paper with particular attention devoted to differential diagnostic considerations.

High proliferative activity excludes dermatofibroma: report of the utility of MIB-1 in the differential diagnosis of selected fibrohistiocytic tumors.

CONTEXT: Dermatofibroma is a benign fibrohistiocytic tumor composed of a mixture of fibroblastic and histiocytic cells. The diagnosis of this tumor is generally uncomplicated; however, rare variants may be difficult to distinguish from malignant fibrohistiocytic tumors. Deep penetrating dermatofibroma may be difficult to distinguish from dermatofibrosarcoma protuberans, and pseudosarcomatous dermatofibroma and dermatofibroma with monster giant cells share morphologic similarities with malignant fibrous histiocytoma and atypical fibroxanthoma. OBJECTIVE: To find an immunohistochemical marker or markers that differentiate between fibrohistiocytic lesions of skin. DESIGN: We evaluated the immunophenotypic characteristics of 83 fibrohistiocytic tumors (36 typical dermatofibromas, 16 cases of dermatofibrosarcoma protuberans, 16 malignant fibrous histiocytomas, and 15 atypical fibroxanthomas) using antibodies against MIB-1 (Ki-67), factor XIIIa, CD34 (HPCA-1), HHF35 (muscle-specific actin), 1A4 (smooth muscle actin), cytokeratin (AE1/AE3, CAM 5.2, and 34betaE12), S100 protein, and desmin. RESULTS: A high proliferative index detected by MIB-1 staining excluded the possibility of dermatofibroma and was diagnostically useful in separating this entity from dermatofibrosarcoma protuberans, malignant fibrous histiocytoma, and atypical fibroxanthoma. A low proliferative index, however, could not differentiate dermatofibroma from dermatofibrosarcoma protuberans. Factor XIIIa reactivity was not helpful for the diagnosis of dermatofibroma, whereas CD34 reactivity was statistically significant in the diagnosis of dermatofibrosarcoma protuberans. The sensitivity of these 2 markers is low and therefore of questionable practical diagnostic value. CONCLUSION: Evaluation of the proliferative index may further assist in distinguishing dermatofibroma from dermatofibrosarcoma protuberans, atypical fibroxanthoma, and malignant fibrous histiocytoma.