Gene fusions in superficial mesenchymal neoplasms: Emerging entities and useful diagnostic adjuncts

Cutaneous mesenchymal neoplasms are diagnostically challenging because of their overlapping morphology, and, often, the limited tissue in skin biopsy specimens. Molecular and cytogenetic techniques have identified characteristic gene fusions in many of these tumor types, findings that have expanded our understanding of disease pathogenesis and motivated development of useful ancillary diagnostic tools. Here, we provide an update of new findings in tumor types that can occur in the skin and superficial subcutis, including dermatofibrosarcoma protuberans, benign fibrous histiocytoma, epithelioid fibrous histiocytoma, angiomatoid fibrous histiocytoma, glomus tumor, myopericytoma/myofibroma, non-neural granular cell tumor, CIC-rearranged sarcoma, hybrid schwannoma/perineurioma, and clear cell sarcoma. We also discuss recently described and emerging tumor types that can occur in superficial locations and that harbor gene fusions, including nested glomoid neoplasm with GLI1 alterations, clear cell tumor with melanocytic differentiation and ACTIN::MITF translocation, melanocytic tumor with CRTC1::TRIM11 fusion, EWSR1::SMAD3-rearranged fibroblastic tumor, PLAG1-rearranged fibroblastic tumor, and superficial ALK-rearranged myxoid spindle cell neoplasm. When possible, we discuss how fusion events mediate the pathogenesis of these tumor types, and we also discuss the related diagnostic and therapeutic implications of these events.

Angiomatoid Fibrous Histiocytoma, A Great Mimicker -A Short Series of 3 Cases with EWSR1 Fusion

Angiomatoid Fibrous histiocytoma (AFH) is a rare soft tissue neoplasm that is often misdiagnosed initially. It is commonly encountered in the superficial extremities of children and young adults. It is composed of a nodular proliferation of bland looking spindled to ovoid cells, some with variant histology and characterized by EWSR1 fusion. We, herein, present three such cases, who presented with swelling in the right leg (case 1), right forearm (case 2), and right thigh (case 3). Case 2 presented in the fourth decade with a large swelling compared to the other two cases that presented in 3rd decade with a small swelling. Histologic examination of case 2 showed extensive myxoid changes making it diagnostically challenging. All three cases showed EWSR1 fusion with a break-apart probe. Follow-up was uneventful in all three cases. AFH, although it is a benign neoplasm, is a great mimicker of various low-grade spindle cell sarcomas. Awareness of this entity with its various histomorphological variants is necessary to accurately diagnose this lesion.

Meningioma and Other Meningeal Tumors

Meningiomas develop from meningothelial cells and approximately account for more than 30 percent of central nervous system (CNS) tumors. They can occur anywhere in the dura, most often intracranially and at dural reflection sites. Half of the cases are usually at parasagittal/falcine and convexity locations; other common sites are sphenoid ridge, suprasellar, posterior fossa, and olfactory groove. The female-to-male ratio is approximately 2 or 3-1, and the median age at diagnosis is 65 years. Meningiomas are generally extremely slow-growing tumors; many are asymptomatic or paucisymptomatic at diagnosis and are discovered incidentally. Clinical manifestations, when present, are influenced by the tumor site and by the time course over which it develops. Meningiomas are divided into three grades. Grade I represents the vast majority of cases; they are considered typical or benign, although their CNS location can still lead to severe morbidity or mortality, resulting in a reported ten-year net survival of over 80%. Atypical (WHO grade II) meningiomas are considered "intermediate grade" malignancies and represent 5-7% of cases. They show a tendency for recurrence and malignant degeneration with a relevant increase in tumor cell migration and surrounding tissue infiltration; ten-year net survival is reported over 60%. The anaplastic subtype (WHO III) represents only 1-3% of cases, and it is characterized by a poor prognosis (ten-year net survival of 15%). The treatment of choice for these tumors stands on complete microsurgical resection in case the subsequent morbidities are assumed minimal. On the other hand, and in case the tumor is located in critical regions such as the skull base, or the patient may have accompanied comorbidities, or it is aimed to avoid intensive treatment, some other approaches, including stereotactic radiosurgery and radiotherapy, were recommended as safe and effective choices to be considered as a primary treatment option or complementary to surgery. Adjuvant radiosurgery/radiotherapy should be considered in the case of atypical and anaplastic histology, especially when a residual tumor is identifiable in postoperative imaging. A "watchful waiting" strategy appears reasonable for extremely old individuals and those with substantial comorbidities or low-performance status, while there is a reduced threshold for therapeutic intervention for relatively healthy younger individuals due to the expectation that tumor progression will inevitably necessitate proactive treatment. To treat and manage meningioma efficiently, the assessments of both neurosurgeons and radiation oncologists are essential. The possibility of other rarer tumors, including hemangiopericytomas, solitary fibrous tumors, lymphomas, metastases, melanocytic tumors, and fibrous histiocytoma, must be considered when a meningeal lesion is diagnosed, especially because the ideal diagnostic and therapeutic approaches might differ significantly in every tumor type.

A Rare Entity of Undifferentiated Pleomorphic Sarcoma of the Mandible - A Case Report

The Rationale:

Undifferentiated pleomorphic sarcoma originally known as malignant fibrous histiocytoma was declassified by the World Health Organization in 2002 as a formal diagnostic entity and renamed as an undifferentiated pleomorphic sarcoma. It accounts for <1% of malignant tumours of the long bone.

Patient Concerns:

A 33-year-old male patient reported with swelling and pain in the lower left posterior jaw region for 3 months with a history of fall on the floor 3 months back.

Diagnosis:

On examination, diffuse solitary swelling was present on the left lower third of the face and was diagnosed radiographically and histopathologically as undifferentiated pleomorphic sarcoma of the mandible.

Treatment and Outcomes:

Selective neck dissection, followed by reconstruction with fibula osteomyocutaneous flap and then referred for adjuvant radiotherapy.

Take-away Lessons:

Vimentin staining plays a substantial role in the diagnosis of undifferentiated pleomorphic sarcoma. A long-term follow-up after treatment is required to increase the chances of disease-free survival for the patients.

Fibrous Histiocytoma of Anterior Ethmoidal Sinus: Case Report and Review of the Literature

Benign fibrous histiocytoma of the para nasal sinus is a rare tumor of this region which originates from mesenchymal cells. A 9-year-old girl presented with gradually enlarging mass above the medial canthus over 3 months. Orbital computerized tomography scan showed a round well-differentiated homogeneous mass in the anterior ethmoidal sinus. Histology and immunohistochemistry analysis after excision revealed proliferation of spindle-shaped fibroblasts in storiform pattern and histiocytes without mitosis and anaplasia. After 9 months from surgical excision, recurrence occurred which resulted in total excision again. This is the first reported case of benign fibrous histiocytoma involving the ethmoid sinus in Iranian people. Rare sinus tumor should be considered in the differential diagnosis of sinus tumors.

Conjunctival and Corneal Fibrous Histiocytoma: Brief review

Background: Fibrous histiocytoma (FH), a mesenchymal tumour, usually have an orbital presentation. Rarely, FH in both benign and malignant forms have been reported at limbus and conjunctiva. Present narrative review was conducted to determine demographic profile, clinical presentation and management options for this rare tumour.Methods: PubMed database was searched to identify articles presenting with fibrous histiocytoma of conjunctiva, cornea and limbus. Data was tabulated for age of presentation, sex, eye involved, area of involvement, if tumor was benign or malignant, management and recurrences.Results: Total of 35 articles were selected, which included 42 cases, of which 27 were benign and 15 malignant. 25 cases showed presence of limbal FH, 12 conjunctival, 4 caruncular and 1 corneal FH. Mean age of presentation was 30.9 years with male preponderance (females-10, males-17) in benign FH while malignant FH presented with mean age of 44.5 years and sex distribution of 7 females and 8 males. 4 cases of benign FH showed recurrence, which required re-excision and immunotherapy, while recurrence in malignant FH was 60%, where 4 needed exenteration, 3 enucleation and 1 expired due to metastasis.Conclusion: FH is one of the rare ocular tumours of eye presenting usually at the limbus and conjunctiva and rarely cornea. Histopathological examination along with immunostaining has a definite role in the diagnosis. Surgical excision with tumour free margins is the corner stone of treatment. Recurrences in benign varieties need re-excision or immunotherapy, while malignant cases need aggressive surgical options like exenteration or enucleation.

Fibrous histiocytoma/dermatofibroma in children: the same as adults?

Fibrous histiocytoma (FH) or dermatofibroma is a common cutaneous lesion mostly seen in adults and rare in the first two years of life. Two hundred sixty-seven patients younger than 18 years with a diagnosis of FH or dermatomyofibroma, a lesion with morphologic overlap with FH, were identified from the files of a single institution, with only 13 (4.8%) occurring in patients younger than 5 years. Ten patients had either underlying neurologic, autoimmune, or metabolic disorders or a family history of autoimmune conditions. Histologic review of hematoxylin and eosin staining and immunostaining on 75 FHs and dermatomyofibroma in 70 patients showed the following results: 33 classic FHs, 8 classic FHs characterized by a peculiar retiform morphology with thin fascicles of elongated cells forming a network reminiscent of the eruptive variant of FH, 19 deep/cellular variants, 5 aneurysmal variants, 3 lipidized variants (including two lesions in a patient affected by mucopolysaccharidosis IV), 3 dermatomyofibromas, and 4 isolated cases of hemosiderotic, granular cell atypical, and epithelioid FH. Immunostaining for factor XIIIa highlighted a dense network of dendritic cells in FH, which was significantly reduced in the FH with retiform morphology. Smooth muscle actin staining was positive in a high percentage of FHs (85.3%). The current series demonstrates that FH in children may show unique clinical and morphologic features. The retiform pattern with decreased dendritic cells found in congenital lesions and in two older patients with lesions in two locations might have a different pathogenesis, probably related to an altered immune response in very young patients.

[Clinicopathologic and molecular characteristics of myxoid angiomatoid fibrous histiocytoma]

Objective: To investigate the molecular genetic and clinicopathologic characteristics, immunophenotypes, diagnostic and differential diagnostic features of myxoid angiomatoid fibrous histiocytoma (MAFH). Methods: Three cases of MAFH were collected from the archives of Zhejiang Provincial People's Hospital between January 2015 to August 2018. The clinical and radiologic features, histomorphology, immunohistochemistry, molecular genetics and prognosis were analyzed. Results: Patients consisted of 2 women and 1 man aged 37 years, 46 years, and 57 years, respectively. The clinical manifestations of 3 patients were presented as a painless, slowly-enlarged mass with a duration ranging of 2 weeks, 2 months and 50 years. These tumors were located at the deep somatic soft tissue of extremities or limbs (right hip, left forearm, left wrist, respectively) and 2 were preoperatively considered as ganglion cyst or giant cell tumor of tendon sheath by imaging examinations. The diameter of circumscribed mass lesion was ranged from 3.0 to 7.5 cm, which exhibited a gray white to tan and gelatinous cut surface. Extensive hemorrhage and cystic changes were observed in 2 cases. Under low magnification, all tumors showed a dense fibrous pseudo-capsule with a peritumoral lymphoplasmacytic cuff and a multi-nodular growth pattern. Blood-filled cystic spaces were observed in 2 tumors. The myxoid stroma occupied 60.0%, 80.0% and 90.0% area of the entire tumor, respectively. Within the myxoid areas, tumor cells were oval to stellate and arranged in cord-like, microcystic and reticular growth patterns. Transitions of myxoid tumor components to more solid areas with typical histology of angiomatoid fibrous histiocytoma (AFH) were observed at least focally in all the three cases. The tumor cells exhibited minimal atypia and scarce mitoses (1 to 2/50 HPF) without necrosis, and prominently focal intracytoplasmic vacuoles were identified in one case. The results of immunohistochemistry staining showed that, 2/3 cases focally expressed desmin, 2/3 focally expressed epithelial membrane antigen (EMA), and 1/3 focally expressed CD99. The positive index of Ki67 was approximately 1% to 5%. Fluorescence in situ hybridization analysis showed that EWSR1 gene rearrangement occurred in all of the three cases. During the period of follow-up, one case showed local recurrence at 15 months, one case showed postoperative recurrence at 24 months, and the recurrent tumor slowly grew for 120 months until the second resection, without recurrence at the following 2 months. The left case showed a disease-free survival at 32 months. Conclusions: MAFH is a rare subtype of AFH with a low-grade behavior and may lead to diagnostic confusions. Carefully searching for the typical AFH histomorphology and combining with EWSR1 gene rearrangement test can help to distinguish MAFH from other mimickers.

A rare case of benign fibrous histiocytoma of the cornea

Fibrous histiocytoma (FH) commonly occurs in the superficial layers of the skin. Orbit and limbus are documented ophthalmic sites of involvement but isolated corneal FH has never been reported in literature. We present the first case of FH exclusively involving the cornea where a 10-year-old male child presented with a 3-month history of a painless growth on the superior cornea of the right eye with deterioration of vision. Tumor excision with therapeutic penetrating keratoplasty was done and the histopathological examination confirmed the diagnosis. There was no recurrence and the corneal graft was clear at 1 year.

Corneoscleral locally aggressive fibrous histiocytoma in Xeroderma Pigmentosum patient: A case report

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder that has been found in all continents and racial groups in relation to faulty repair of DNA with sun exposure. Several cutaneous and ocular tumors have been described in relation to XP including fibrous histiocytoma (FH). The diagnosis of conjunctival FH is challenging owing to the rarity of this tumor and the diversity of its classification into benign, locally aggressive and malignant. We are describing a recurrent FH exhibiting a locally aggressive behavior in a child with history of XP. Detailed histopathological features are presented with literature review.

Epithelioid cell histiocytoma with SQSTM1-ALK fusion: a case report

Background

Epithelioid cell histiocytoma (ECH), which is also known as epithelioid benign fibrous histiocytoma, has been classified as a rare variant of fibrous histiocytoma (FH). However, the recent detection of ALK protein expression and/or ALK gene rearrangement in ECH suggests that it might be biologically different from conventional FH.

Case presentation

A 27-year-old male presented with nodule on his left foot, which had been present for 5 years. A macroscopic examination revealed an exophytic, hyperkeratotic nodule on the dorsum of the left foot. Tumorectomy was performed, and a microscopic examination showed a subepidermal lesion composed of sheets of tumor cells with oval to round nuclei and ill-defined eosinophilic cytoplasm. The tumor cells were diffusely positive for factor XIIIa and ALK, but were negative for AE1/AE3 keratin, alpha-smooth muscle actin, CD30, CD34, CD68, PU.1, melan A, MITF, and S-100 protein. ALK immunostaining showed a diffuse cytoplasmic staining pattern. ALK fluorescence in situ hybridization demonstrated break-apart signals, which was suggestive of ALK rearrangement. A 5′-rapid amplification of cDNA ends assay detected SQSTM1-ALK fusion, in which exon 5 of the SQSTM1 gene was fused to exon 20 of the ALK gene. The patient was free from recurrence and distant metastasis at the 1-year of follow-up.

Conclusion

We were able to demonstrate the SQSTM1-ALK fusion gene in ECH. Practically, detecting immunopositivity for ALK and appropriate cell-lineage markers are the key to diagnosing ECH.

CD34 + tumours of the orbit including solitary fibrous tumours: a six-case series

Background

To report six cases of CD34+ fibroblastic mesenchymal tumours, which are uncommon neoplasms in the orbit.

Case presentation

Six patients presenting with proptosis and palpable mass who were later diagnosed with fibrous solitary tumours, fibrous histocytoma or haemangiopericytoma in the orbit were included. All patients received radiologic examinations and surgical excision for histopathology and immunohistochemistry examinations. Five patients had no recurrence after a minimum follow-up of 12 months. One patient (case 6) experienced recurrence twice, and had debulking surgeries each time. At present, the patient still has remnant tumour in the orbit, but no growth has been detected during the past two years. The tumour size will be closely monitored.

Conclusions

Even though fibroblastic tumours are rarely found in the orbit, they can present as a palpable mass with proptosis. Complete surgical excision is important for long-term prognosis, and immunohistochemical study is helpful for confirming pathologic diagnosis.

A Squamous Cell Carcinoma and a Malignant Fibrous Histiocytoma Developing in a Patient with a Mature Cystic Teratoma

We present a very rare case of malignant transformation of a benign mature cystic teratoma. The pathology report revealed malignant transformation of both the epithelial and sarcomatous elements of a benign dermoid cyst. To the best of our knowledge, this appears to be the third case of a malignant fibrous histiocytoma and a squamous cell carcinoma developing from a mature cystic teratoma. Malignant transformation of a dermoid cyst is usually diagnosed postmenopausally, but our patient was premenopausal. The etiology and prognosis of malignant transformation of this benign condition remain unknown.

Intracranial benign fibrous histiocytoma mimicking parasagittal meningioma: report of two cases and review of literature

Primary benign fibrous histiocytoma involving the central nervous system is an exceedingly rare tumor with most cases originating from the dura or parenchymal tissue. Diagnosis of primary benign fibrous histiocytoma is difficult due to its confusing histopathological characteristics. Two cases of primary intracranial benign fibrous histiocytoma mimicking parasagittal meningioma are presented in this report. Both tumors were gross totally resected and the patients showed no evidence of recurrence at follow-up of 12 months. The clinical features and prognosis of this rare tumor that were reported previously in the literature were also reviewed. Histopathological examination coupled with immunohistochemical staining is proved to be the convincing diagnostic method for the primary benign fibrous histiocytoma. Surgical resection is the recommendation for the therapy of the tumor.

Benign fibrous histiocytoma presenting as anal canal polyp: first case report

Nonepithelial and nonmelanocytic anal neoplasms are uncommon. The majority are mesenchymal tumors, most of which are malignant sarcomas, particularly leiomyosarcomas and gastrointestinal stromal tumors. Benign mesenchymal anal neoplasms are even rarer. The most common reported cases were anal leiomyomas, granular cell tumors, fibroadenomas, and xanthogranulomas. Benign fibrous histiocytomas (BFHs) or dermatofibromas are common mesenchymal cutaneous tumors that occur in different sites and at any age. Review of the literature did not show previous reports of BFH arising in the anal canal region. We report the first case of a solitary BFH, an unexpected occurrence of a common tumor type presenting as a polyp in an unusual site such as the anus. This rare occurrence can present diagnostic challenges for the surgeons and pathologists. Clinically, it can be confused with the usual anal tags, fibroepithelial polyps, or hemorrhoids. Benign fibrous histiocytoma is a neoplasm with a potential of local recurrence and, therefore, carries certain clinical implications for the patients' management and follow-up when compared with the common nonneoplastic causes of anal polyps such as the anal tags of anal fissures, hemorrhoids, or fibroepithelial papilla. Histologically, it should be differentiated from other histiocytic lesions. This can be resolved by the application of certain histologic features with the appropriate immunohistochemical markers taken within the correct clinical context.

Subcutaneous dermatofibroma

Dermatofibroma (DF) is usually confined to the dermis and the overlying epidermis is usually hyperplastic. Although DF with deep subcutaneous extension is commonly encountered, purely subcutaneous DF is uncommon. In this review, we describe a case of a 41-year-old male patient who presented with a painless, subcutaneous, hard papule on the left thigh. After the skin had been incised the lesion was totally removed, and histopathology revealed a subcutaneous dermatofibroma.

A rare case of fibrous histiocytic tumor of the tongue

Fibrous histiocytoma is a benign soft tissue tumor composed of a mixture of fibroblastic and histiocytic cells arising as a fibrous mass everywhere in the human body. Based on location it is divided into cutaneous type and those involving the deeper tissues. Involvement of the oral cavity is rare. It is important to distinguish this tumor from the more aggressive forms of fibrohistiocytic neoplasm including dermatofibrosarcoma protuberans and malignant fibrous histiocytoma (FH) (7).The clinical and histiological diagnosis, treatment, and prognosis of FH have been discussed.

Giant hemosiderotic dermatofibroma: a case report and review of the literature

Dermatofibroma is a common benign fibrohistiocytic lesion that usually appears as a slow-growing, firm dermal nodule with a predilection for the legs of middle-aged women. They are usually smaller than 2 cm in diameter. Many histological variants have been described. Generally, the clinical and histological diagnosis is straightforward, but differentiating it from other cutaneous tumors can be difficult in atypical cases and rare variants. Giant dermatofibroma is a rare clinical variant of dermatofibroma and less than 25 cases have been reported. It is characterized essentially by its unusually large size, which often mimics malignant tumors clinically. We first present the case of a giant hemosiderotic dermatofibroma in a 54-year-old patient, who presented with a large ulcerated mass of the left foot which was excised, and then review the literature briefly.