Recent Advances in the Diagnosis, Pathogenesis, and Management of Myxoinflammatory Fibroblastic Sarcoma

Myxoinflammatory fibroblastic sarcoma (MIFS) is an infiltrative, locally aggressive fibroblastic neoplasm of intermediate malignancy that typically arises in the distal extremities of middle-aged adults. It can histologically be confused with a number of benign and malignant conditions. Recently, high-grade examples of MIFS have been described. Immunohistochemistry plays a very limited role in the diagnosis of MIFS. Several genetic alterations have been identified in MIFS, including a t(1;10)(p22;q24) translocation with TGFBR3 and/or OGA rearrangements, BRAF rearrangement, and VGLL3 amplification. Although it appears that VGLL3 amplification is the most consistent alteration, the molecular pathogenesis of MIFS remains poorly understood. A wide resection is considered the standard treatment for MIFS. Radiotherapy may be a viable option in cases with inadequate surgical margins or cases where surgery is likely to cause significant functional impairment. The systemic treatment options for advanced or metastatic disease are very limited. This review provides an updated overview of the clinicoradiological features, pathogenesis, histopathology, and treatment of MIFS.

[Myxoinflammatory fibroblastic sarcoma of the lower limb]

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare, low-grade, painless tumor of mesenchymal origin. In the current, 5th edition of the World Health Organisation (WHO) 'Classification of tumors: Soft tissue and bone tumors', there is no exact diagnostic genetic alteration defined in MIFS. Hereby we present the case of a 71-year-old female patient, with a medical history of benign essential hypertension, who visited the hospital because of a lesion above her right shin. She perceived the lesion 1.5 years prior to the medical attendance, and she only attended the medical facility because of the development of pain, erosion and papule formation on the skin surface. Microscopically, the lesion had cellular and pleomorphic appearance with nodular structure, and showed honeycomb-like infiltration of the subcutaneous fat tissue. Tumor cell infiltration was visible among the collagen fibers of the dermis. Tumor cells frequently displayed multinuclear morphology with prominent, viral inclusion-like nucleoli and exuberant fibrillary, often vacuolated and ground-glass cytoplasm. With immunohistochemical examination, tumor cells showed multifocal positivity with CD34, CD31, podoplanin (D2-40), cyclin D1, and epithelial membrane antigen (EMA). Furthermore, the tumor cells proved to be diffusely positive with smooth muscle actin (SMA). After meeting all the essential criteria of the current WHO classification, the case was concluded as MIFS, showing high-grade features. According to our experience, an immunohistochemistry panel of podoplanin, ciklin-D1, CD10, EMA, CD34, and CD31 can facilitate the correct conclusion. Our case of MIFS highlights the unusual, focally high-grade features of this complicated, challenging disease. Diffuse SMA positivity is a known, but uncommon feature of these tumors. Orv Hetil. 2023; 164(41): 1637-1641.

Malignant undifferentiated epithelioid neoplasms with MAML2 rearrangements: A clinicopathologic study of seven cases demonstrating a heterogenous entity

Among mesenchymal tumors, MAML2 gene rearrangements have been described in a subset of composite hemangioendothelioma and myxoinflammatory fibroblastic sarcoma (MIFS). However, we have recently encountered MAML2-related fusions in a group of seven undifferentiated malignant epithelioid neoplasms that do not fit well to any established pathologic entities. The patients included five males and two female, aged 41-71 years old (median 65 years). The tumors involved the deep soft tissue of extremities (hip, knee, arm, hand), abdominal wall, and the retroperitoneum. Microscopically, the tumors consisted of solid sheets of atypical epithelioid to histiocytoid cells with abundant cytoplasm. Prominent mitotic activity and necrosis were present in 4 cases. In 3 cases, the cells displayed hyperchromatic nuclei or conspicuous macronucleoli, and were admixed with background histiocytoid cells and a lymphoplasmacytic infiltrate. By immunohistochemistry (IHC), the neoplastic cells had a nonspecific phenotype. On targeted RNA sequencing, MAML2 was the 3' partner and fused to YAP1 (4 cases), ARHGAP42 (2 cases), and ENDOD1 (1 case). Two cases with YAP1::MAML2 harbored concurrent RAF kinase fusions (RBMS3::RAF1 and AGK::BRAF, respectively). In 2 cases with targeted DNA sequencing, mutations in TP53, RB1 and PTEN were detected in 1 case, and PDGFRB mutations, CCNE1 amplifications and CDKN2A/2B deletion were detected in another case, which showed strong and diffuse PDGFRB expression by IHC. Of the 4 cases with detailed clinical history (median follow-up period 8 months), three developed distant metastatic disease (one of which died of disease); one case remained free of disease 3 years following surgical excision. In conclusion, we describe a heterogeneous series of MAML2-rearranged undifferentiated malignant epithelioid neoplasms, a subset of which may overlap with a recently described MIFS variant with YAP1::MAML2 fusions, further expanding the clinicopathologic spectrum of mesenchymal neoplasms with recurrent MAML2 gene rearrangements.

Myxoinflammatory Fibroblastic Sarcoma of Eyeball in an Infant: A Rare Presentation

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare soft tissue neoplasm most commonly occurring in the distal extremities of adult patients. It is a low-grade neoplasm with high rate of local recurrence but low rate of metastasis. We describe a case of MIFS of eyeball in an infant. An enucleation surgery was performed, and on the basis of histopathological and immunohistochemical evaluation, a diagnosis of MIFS was rendered. Till date more than 400 cases of MIFS have been reported with only a single case report of MIFS in an adult in iris. To the best of our knowledge, ours is the first case of MIFS in the eye in a child. Considering its rarity in children and especially in an infant (this seems to be the youngest patient in the literature), close follow-up is essential as the biology of these lesions cannot be predicted.

Superficial CD34-positive fibroblastic tumor in the forearm of a middle-aged patient: A newly described, rare soft-tissue tumor

Superficial CD34-positive fibroblastic tumor is a recently described soft-tissue tumor entity. A 48 year-old-male presented with a gradually increasing soft-tissue mass in his right forearm of 2 years' duration, along with multiple subcutaneous soft-tissue nodular lesions, and reminiscent of lipomas over his body. He underwent a wide excision of his forearm mass. Microscopic sections showed a circumscribed tumor in the dermis and subcutaneous fat, composed of spindle cells, inflammatory cells, including lymphocytes, plasma cells, and eosinophils, along with interspersed markedly pleomorphic giant cells containing moderate-to-abundant "glassy" cytoplasm, vesicular nuclei, exhibiting prominent nucleoli, and intranuclear pseudoinclusions. There were no significant mitotic figures, areas of hemorrhage, necrosis, or pigment histiocytes. By immunohistochemistry, the tumor cells were diffusely positive for CD34 while negative for cytokeratin (CK), pan CK (AE1/AE3), S100 protein, CD30, and CD31. MIB1/Ki-67 was low and highlighted 4%-5% tumor nuclei. Diagnosis of superficial CD34-positive fibroblastic tumor was offered. Sections from the various resection margins were free of tumor. Postresection, the patient is alive with no evidence of disease for the past 8 months. This constitutes as one of the first case reports of this rare tumor entity from our country. Its diagnostic and treatment implications are discussed herewith.

Large cervicothoracic myxoinflammatory fibroblastic sarcoma with brachial plexus invasion: A case report and literature review

Myxoinflammatory fibroblastic sarcoma is a rare sarcoma that develops in patients of all ages, which usually presents as a slow-growing painless mass in the distal extremities. To date, myxoinflammatory fibroblastic sarcoma with invasion of the brachial plexus has rarely been reported in the literature. In this study, a case of large cervicothoracic sarcoma, which invaded the brachial plexus, is presented. The patient reported no sensory disturbance or dyskinesia. The tumor was completely resected without injury of the brachial plexus. The postoperative histological diagnosis was myxoinflammatory fibroblastic sarcoma. Follow-up examination performed 24 months after surgery revealed no tumor recurrence and no sensory disturbance or dyskinesia was reported. This study presents a rare case of large myxoinflammatory fibroblastic sarcoma with brachial plexus invasion that was successfully managed by surgery.

Myxoid soft-tissue neoplasms: comprehensive update of the taxonomy and MRI features. AJR Am J Roentgenol. 2015;204:374-385. [PMID: 25615761 DOI: 10.2214/ajr.14.12888]

OBJECTIVE. The purpose of this article is to review the classification, clinical presentation, and histopathologic and MRI features of myxoid soft-tissue neoplasms. CONCLUSION. MRI is the modality of choice for characterization of myxoid soft-tissue tumors. A combination of imaging features (including certain characteristic signs), clinical features, and patient demographics can help the radiologist in coming to a specific diagnosis or in narrowing down the differential diagnoses.

Myxoinflammatory fibroblastic sarcoma of the scalp: aggressive behavior at a rare, nonextremity site

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare low-grade malignant soft tissue neoplasm, which usually presents on the distal extremities of adults and sometimes children. It has a characteristic appearance, of a lobulated or multinodular neoplasm of moderately atypical epithelioid or spindled cells, vacuolated cells, and enlarged or bizarre cells with macronuclei, with prominent mixed inflammatory infiltrate, and variably myxoid stroma. However, the proportions of each component vary, making diagnosis difficult, particularly when tumors arise at unusual nonextremity sites. We describe a case of MIFS occurring as a primary neoplasm on the scalp of an 80-year-old male, which recurred locally after 2 years and developed extensive bilateral cervical lymph node metastases. MIFS is exceptionally rare in the head and neck, and it has been described only once on the scalp. This case showed classical histologic features, and additionally a high mitotic index and atypical mitoses, which may be suggestive of a poorer prognosis. This case highlights the need to consider MIFS in the differential diagnoses of pleomorphic tumors of the head and neck, and it adds to the small number of MIFS showing highly aggressive behavior.

Myxoinflammatory fibroblastic sarcoma: a clinicopathologic analysis of 104 cases, with emphasis on predictors of outcome

In this study, we examine the clinicopathologic features of 104 cases of myxoinflammatory fibroblastic sarcoma (MIFS), a low-grade, inflammatory fibromyxoid tumor with a predilection to distal extremity soft tissue, and attempt to identify factors predictive of aggressive behavior. The study cohort consisted of 49 male and 55 female patients ranging in age from 17 to 83 (mean, 42; median, 39) years. The tumor arose primarily on the dorsal aspect of the distal extremities as a solitary and usually painless mass. Tumors ranged in size from 0.5 to 15 (mean, 3.2; median; 2.4) cm. Microscopically, tumors consisted of variably cellular and inflamed fibromyxoid tissue growing as a lobulated mass or as multiple nodules within subcutaneous tissue or along tendinofascial planes. Tumor cells ranged from plump spindled to more epithelioid cells with enlarged, vesicular nuclei. Characteristic of the process was a strikingly bizarre cell with an inclusion body-like nucleolus (85% of cases) and/or a smudgy hyperchromatic nucleus (51%) present in all but 7 cases. The mitotic rate per 50 high-power field ranged from 0 to 13 (mean, 2,9; median, 2) mitoses. Twenty-two tumors demonstrated 1 or more of the following atypical features: (1) foci with complex sarcoma-like vasculature; (2) hypercellular areas; and (3) increased mitotic activity or atypical mitotic figures. Immunohistochemically, tumor cells demonstrated immunoreactivity for vimentin (100%), D2-40 (86%), CD34 (50%), keratin(s) (33%), CD68 (27%), actin(s) (26%), desmin (9%), S-100 protein (7%), and epithelial membrane antigen (6%). Thirty of 59 patients (51%) with follow-up data suffered (at least) 1 local recurrence, and 1 patient developed metastatic disease after multiple local recurrences. Completeness of initial surgical excision was the only clinicopathologic parameter that statistically correlated with a lower incidence of recurrence (P=0.004). Histologically atypical MIFS recurred more often than conventional tumors (67% vs. 47%), but the difference was not statistically significant (P=0.35). Our study shows that histologic features often associated with more aggressive sarcomas do not substantially impact the morbidity of MIFS, and complete surgical excision provides the best chance for disease-free survival.

Myxoinflammatory fibroblastic sarcoma of the thigh: A morphologic diversity

Myxoinflammatory fibroblastic sarcoma (MIFS)/acralmyxoinflammatory fibroblastic sarcoma (AMFS) is a rare, painless, low-grade neoplasm which commonly occurs in the extremities. It has a distinctive morphology and can be a diagnostic challenge, simulating inflammatory conditions as well as neoplastic conditions. They are low-grade sarcomas with a protracted clinical course, a high rate of local recurrence and a low rate of metastasis. We report a case of proximal MIFS in a 50-year-old woman who presented with a mass in the thigh.