Myoid Tumor Research Articles

Pediatric-type Myoid Neoplasms of Somatic Soft Tissue: A Clinicopathological and Molecular Genetic Study of 78 Tumors, Highlighting Indolent Clinical Behavior and Frequent SRF Gene Rearrangements.

Soft tissue tumors with smooth muscle differentiation are rare in pediatric patients. Despite often showing morphologic features sufficient for classification as "leiomyosarcoma" in adults (e.g., high cellularity, mitotic activity), clinical follow-up has shown only indolent behavior. The pathological features of recently reported SRF-rearranged "cellular myofibromas/myopericytomas", typically occurring in children, overlap with those of true smooth muscle tumors. We studied a large series of pediatric tumors with morphologic and immunohistochemical evidence of smooth muscle differentiation, with the goals of better understanding their natural history and molecular genetic features. Seventy-eight tumors were identified occurring in 45 males and 33 females, with a median age of 10 years. Clinical follow-up (50 patients; median 45.5 months) disclosed local recurrence in 7 patients (15%). No metastases or deaths due to disease occurred. Group 1 (73/78) tumors consisted of cellular fascicles of mildly to at most moderately atypical, bland, ovoid to spindled cells with distinctly eosinophilic cytoplasm, appreciable mitotic activity (median 5/50 HPF) and no necrosis. Group 2 tumors (5/78) showed greater cellularity, significant nuclear pleomorphism, and brisk mitotic activity (median 59/50 HPF). Subsets of group 1 tumors harbored SRF rearrangements (16/47) and all group 2 tumors showed TP53 biallelic inactivation (5/5). SRF fusion partners included CITED1, NCOA2, C3orf62, RELA, ARGFXP1, ARNTI2, ICA1L, and unknown (n=1). We conclude that the prognosis for pediatric tumors with smooth muscle differentiation that fall into group 1 is excellent. SRF rearrangements are present in a significant minority of tumors, typically showing features of smooth muscle, rather than myopericytic differentiation. A smaller subset with more worrisome morphologic features harbor biallelic inactivation of TP53. To emphasize their unique features, we propose the term "pediatric-type myoid neoplasms of somatic soft tissue," rather than simply "leiomyoma" or "leiomyosarcoma" for group 1 tumors and the designation of leiomyosarcoma in children should be limited to group 2 tumors.

A Rare Tumor of Intravascular Myopericytoma in the Right Renal Vein.

Myopericytoma, a perivascular myoid neoplasm, is commonly found in the dermis or subcutaneous tissues; however, its occurrence in visceral organs is unusual. Here, we present an extremely rare tumor of intravascular myopericytoma of the right renal vein. A 44-year-old man was incidentally diagnosed with a mass in the right kidney during a routine checkup. A nephrectomy was performed because the urologist suspected renal cancer. A gross examination of the resected specimen revealed a well-circumscribed brown mass in the renal hilum. Histologically, the tumor showed a concentric multilayered proliferation of spindle cells surrounding blood vessels. Immunohistochemical staining showed that the spindle-shaped tumor cells were negative for desmin but positive for α-smooth muscle actin and h-caldesmon, indicating their myoid nature. We confirmed that the tumor was located in the right renal vein because it was encased within a thick wall that was desmin-positive and contained elastic fibers, as shown by Elastica van Gieson staining. The patient was diagnosed with an intravascular myopericytoma of the right renal vein. There are several differential diagnoses for renal mesenchymal tumors, including angiomyolipoma. This emphasizes the importance of considering these uncommon tumors when examining nephrectomy specimens.

Pseudomyogenic Hemangioendothelioma Arising in the Maxillary Sinus, an Uncommon and Misdiagnosed Tumor: A Case Report.

Pseudomyogenic hemangioendothelioma (PMHE) is a rare vascular neoplasm with an intermediate to low-grade malignant potential. Only 5% of PMHEs occur in the head and neck. This tumor exhibits different histological patterns and mimics other vascular tumors, myoid tumors, or carcinomas. The distinction between these tumors can be a very challenging situation for pathologists. In this article, we report the first case, to our knowledge, of PMHE arising in the maxillary sinus, to highlight this uncommon entity and discuss differential diagnoses.

Cellular myofibromas with SRF fusions: clinicopathological and molecular study of 3 cases of a rare entity and a potential mimic of sarcoma

Cellular myofibromas/myopericytomas harboring recurring SRF fusions are recently characterized as rare and diagnostically challenging entities, which can mimic myogenic sarcomas. These tumors belong to the pericytic/perivascular myoid tumor family, which comprises a group of genetically heterogenous and sometimes morphologically overlapping entities. In this series, we describe 3 cases of SRF-rearranged cellular myofibromas/perivascular myoid tumors with a smooth muscle-like phenotype in children. The children ranged from 7 to 16 years of age, and all presented with a painless mass in the extremities, 2 of which were deep-seated. Histologically, the tumors demonstrated a smooth muscle-like morphology and immunophenotype with mild atypia and low-level mitotic activity. Prominent dense collagen deposition and coarse calcification was observed in 2 tumors. RNA sequencing revealed SRF fusions in all cases, with each tumor showing a different 3' partner gene, RELA, NFKBIE, and NCOA3. Of these, NCOA3 has not been reported previously, and this expands the molecular spectrum by identifying a novel fusion partner for SRF. Given that histological features can be worrisome for a myogenic sarcoma, wider awareness of this emerging tumor is valuable to avoid potential misclassification.

Morphological variations of two cases of maxillary myofibromas

The aim of this case report is to depict the varied spectrum of clinical presentation of two cases of solitary myofibromas, one of which was intra-osseous whilst the other presented as a soft tissue lesion. This highlights the spectrum of the clinical presentation of the same pathology. In the most recent World Health Organisation (WHO) 2022 classification of soft tissue tumours, myofibroma is included under the category of myopericytomas. Myopericytoma is a distinctive perivascular myoid neoplasm that forms a morphological spectrum with myofibroma. Molecular evidence has revealed PDGFRB (platelet-derived growth factor receptor beta) mutations in myopericytoma and myofibroma as well as SRF-RELA gene fusions in both lesions confirming a common pathogenesis for both.1 Myofibromas are benign soft tissue neoplasms derived from myofibroblastic cells.2 The term myofibroma refers to a solitary lesion. Myofibromatosis refers to cases in which multiple lesions are present which may affect either one or multiple anatomical locations. Myofibromatosis is almost exclusively seen in young children under the age of 2-years. Myofibromas exhibit a wide age range of clinical presentation and may be present at birth or arise within the first two years of age, but may also present in adults with a significant male predominance. Solitary myofibromas have a predilection to occur in the oral cavity, skin or subcutis of the head, neck and trunk.

SRF Fusions Other Than With RELA Expand the Molecular Definition of SRF-fused Perivascular Tumors.

Pericytic tumors encompass several entities sharing morphologic and immunohistochemical features. A subset of perivascular myoid tumors associated with the SRF-RELA fusion gene was previously described. Herein, we report a series of 13 tumors belonging to this group, in which we have identified new fusion genes by RNA-sequencing, thus expanding the molecular spectrum of this entity. All patients except 1 were children and infants. The tumors, frequently located in the head (n=8), had a mean size of 38 mm (range 10 to 150 mm) and were mostly (n=9) well-circumscribed. Exploration of the follow-up data (ranging from 3 to 68 mo) confirmed the benign behavior of these tumors. These neoplasms presented a spectrum of morphologies, ranging from perivascular patterns to myoid appearance. Tumor cells presented mitotic figures but without marked atypia. Some of these tumors could mimic sarcoma. The immunohistochemical profiles confirmed a pericytic differentiation with the expression of the smooth muscle actin and the h-caldesmon, as well as the frequent positivity for pan-cytokeratin. The molecular analysis identified the expected SRF-RELA fusion gene, in addition to other genetic alterations, all involving SRF fused to CITED1, CITED2, NFKBIE, or NCOA2. The detection of SRF-NCOA2 fusions in spindle cell rhabdomyosarcoma of the infant has previously been described, representing a risk of misdiagnosis, although the cases reported herein did not express MyoD1. Finally, clustering analyses confirmed that this group of SRF-fused perivascular myoid tumors forms a distinct entity, different from other perivascular tumors, spindle cell rhabdomyosarcomas of the infant, and smooth muscle tumors.

Novel SRF-ICA1L Fusions in Cellular Myoid Neoplasms With Potential For Malignant Behavior.

Pericytic tumors comprise a histologic continuum of neoplasms with perivascular myoid differentiation, which includes glomus tumors, myopericytoma, myofibroma, and angioleiomyoma. Despite their morphologic overlap, recent data suggest a dichotomy in their genetic signatures, including recurrent NOTCH gene fusions in glomus tumors and PDGFRB mutations in myofibromas and myopericytomas. Moreover, SRF-RELA fusions have been described in a subset of cellular variants of myofibroma and myopericytoma showing myogenic differentiation. Triggered by an index case of an unclassified cellular myoid tumor showing a novel SRF-ICA1L fusion we have investigated our files for cases showing similar histology and screened them using a combined approach of targeted RNA sequencing and fluorescence in situ hybridization. A fusion between SRF exon 4 and ICA1L exon 10 or 11 was identified in a total of 4 spindle cell tumors with similar clinicopathologic features. Clinically, the tumors were deep-seated and originated in the trunk or proximal lower extremity of adult patients (age range: 23 to 55 y). Histologically, the tumors were composed of cellular fascicles of monomorphic eosinophilic spindle cells showing increased mitotic activity, harboring densely hyalinized stroma, often with focal areas of necrosis. All 4 tumors had similar immunoprofiles with positivity for smooth muscle actin, calponin, and smooth muscle myosin heavy chain. Tumors were negative for desmin and caldesmon, markers often seen in SRF-RELA-positive tumors with similar morphology. Follow-up information was available in 3 patients. Two patients had no evidence of disease, 2 and 5 years after surgical resection. One patient, a 35-year-old male patient with a 19 cm deep-seated tumor with brisk mitotic activity (>20 mitoses in 10 HPF), developed lung metastases 7 years after initial diagnosis. In summary, we report a series of 4 cellular myoid tumors with novel SRF-ICA1L gene fusions, characterized by bland spindle cell fascicular growth, expression of specific smooth muscle markers, elevated mitotic activity, marked stromal hyalinization, focal coagulative necrosis, and potential for malignant behavior. Given the morphologic overlap with related cellular myopericytic tumors with SRF-RELA fusions, it is likely that SRF-ICA1L fusions define a similar subset of neoplasms composed of immature smooth muscle cells.

Clinical and pathologic analysis of myopericytoma in the oral and maxillofacial region

The aim of this study was to analyze myopericytoma in the oral and maxillofacial region in terms of clinical appearance, diagnosis, treatment, and outcomes. Data on 5 new patients with myopericytoma in the oral and maxillofacial region treated at our department were collected and analyzed. There were 2 males and 3 females (age range 10-62 years; mean age 43.8 years). All of the 5 patients presented with masses showing benign biologic behavior. Imaging examinations with use of computed tomography or magnetic resonance imaging showed heterogeneous regions with internal contrast-enhancement or cystic change in 3 cases. All of the patients underwent surgery. Histologic examination showed a broad morphologic spectrum characterized by concentric and perivascular growth of ovoid, plump spindled, and/or round myoid tumor cells. Immunohistochemical examination showed positive staining for vimentin and smooth muscle actin, and negative for CD34 and desmin. During the follow-up period (8-56 months), there was no tumor recurrence. Myopericytoma in the oral and maxillofacial region always exhibits benign biologic behavior and a heterogeneous region with internal contrast-enhancement or cystic change on imaging examinations. Surgery is the first choice of treatment and results in good clinical outcomes.

A Distinct Malignant Epithelioid Neoplasm With GLI1 Gene Rearrangements, Frequent S100 Protein Expression, and Metastatic Potential: Expanding the Spectrum of Pathologic Entities With ACTB/MALAT1/PTCH1-GLI1 Fusions.

ACTB-GLI1 fusions have been reported as the pathognomonic genetic abnormality defining an unusual subset of actin-positive, perivascular myoid tumors, known as "pericytoma with the t(7;12) translocation." In addition, GLI1 oncogenic activation through a related MALAT1-GLI1 gene fusion has been recently reported in 2 unrelated gastric tumors, namely plexiform fibromyxoma and gastroblastoma. Triggered by unexpected targeted RNA-sequencing results detecting GLI1-related fusions in a group of malignant neoplasms with round to epithelioid morphology, and frequently strong S100 protein immunoreactivity, we investigated their clinicopathologic features in relation to other known pathologic entities sharing similar genetics. On the basis of a combined approach of targeted RNA sequencing and fluorescence in situ hybridization screening, we identified 6 cases with GLI1 gene fusions, including 4 fused to ACTB, 1 with MALAT1 and 1 with PTCH1 gene. Patients had a mean age of 36 years at diagnosis (range, 16 to 79 y) and slight female predilection all except 1 tumor originated in the soft tissue. Microscopically, the tumors had a monomorphic epithelioid phenotype arranged in a distinctive nested or cord-like architecture, separated by thin septae and delicate capillary network. All except 2 cases were strongly positive for S100 protein, whereas being negative for SOX10, SMA, and EMA. Only 1 tumor showed focal cytokeratin positivity in rare cells. Although the tumors showed some resemblance to pericytic/glomus tumors or myoepithelial tumors, the immunoprofile was not supportive of either lineage. Moreover, in contrast to the benign course of so-called pericytoma with t(7;12), 3 patients in this series developed metastatic disease to either lymph nodes or lung. In fact the only patient with lung metastases showed a novel PTCH1-GLI1 gene fusion. It remains to be determined whether these tumors represent a clinically and immunohistologically distinct subset of pericytoma, or an altogether novel soft tissue sarcoma. Our findings open new opportunities for targeted therapy, as tumors with GLI1 oncogenic activation, and subsequent PTCH1 overexpression, might be sensitive to sonic hedgehog pathway inhibitors.

Epstein-Barr Virus-Associated Myoid Tumors in Human Immunodeficiency Virus-Infected Patients

Although Epstein Barr Virus (EBV)-associated myoid tumors (EBV-MTs) are a well-recognized entity, commonly associated with immunocompromise and immunosuppression, including Human Immunodeficiency Virus (HIV) infection and acquired immunodeficiency syndrome (AIDS), they are reported uncommonly. An expanding spectrum of EBV-MTs has emerged in the last decade, associated with an increasing range of organ involvement. EBV-MTs are associated with diagnostic pitfalls, incomplete etiopathogenetic understanding and treatment challenges. This review revisits EBV-MTs in the HIV and AIDS setting. The characteristics of EBV, their etiopathogenetic role in neoplasia, in general and in HIV-associated EBV-MTs in particular, are discussed. Historical, demographic and diagnostic clinicopathological features of EBV-MTs are detailed, classification and diagnostic challenges are emphasized, treatment options and dilemmas are presented briefly and outcome-associated factors are described. While attention is drawn to current demographic, classification, etiopathogenetic and management uncertainties and hiatuses, potential future approaches to address these shortcomings are also alluded to.

Unusual soft tissue tumors

In this session, the detailed clinicopathological and genetic findings, and the differential diagnosis of the following five unusual soft tissue tumors will be demonstrated. 1) Inflammatory myofibroblastic tumor occurs in abdominal soft tissue, GI tract, and lung of children and young adult. The prediction of biological behavior is difficult. Cytogenetic study demonstrates ALK rearrangement in more than half cases. 2) Pseudomyogenic hemangioendothelioma is rarely metastasizing endothelial neoplasm. It was initially named as epithelioid sarcoma-like hemangioendothelioma and mimicking myoid tumor or epithelioid sarcoma. FLI1 and ERG are useful markers for this tumor. 3) Myoepithelioma predominantly involve lower or upper limb of young to middle aged adult. This intermediate tumor have broad spectrum of biological behavior, according to cytological atypia. 45% of the tumor shows EWSR1 rearrangement. 4) Malignant rhabdoid tumor is very aggressive tumor and it arises in the deep axial location, such as neck and paravertebral region of infants and children. Tumor cells show the loss of SMARCB1/INI1 protein expression and its gene alterations. 5) PEComa predominantly affects retroperitoneum, uterus and GI tract of female. Definitive criteria of malignant PEComa has not been established yet. The tumor with malignant histology shows aggressive biological behavior.

Myopericytoma of the Facial Cheek

Dear Editor: A 44-year-old woman presented with a painful, solitary nodule on her right cheek. She noticed the flesh-colored nodule several years prior, and the nodule expanded slowly in size. There was no history of trauma. The patient's past medical history and family history were unremarkable. Upon physical examination, a 0.5×0.7 cm-sized, skin-colored, firm nodule on the right cheek was seen (Fig. 1). The biopsy specimen revealed a concentric perivascular proliferation of blank, spindle-shaped myoid-appearing cells (Fig. 2A, B). Immunohistochemical stain showed diffuse immunoreactivity on smooth muscle actin and was negative for desmin (Fig. 2C, D). The CD34 stain highlighted only the endothelium of the vessel, but the perivascular concentric myoid tumor cells were not immunoreactive (Fig. 2E). From the clinicopathological findings, the diagnosis of myopericytoma (MPC) was made. Fig. 1 A 0.5×0.7 cm sized, skin-colored, subcutaneous nodule of the right cheek. Fig. 2 (A) Uncapsulated neoplasm situated in the subcutis (H&E, scanning view). (B) Proliferation of bland round to ovoid cells arranged in a concentric perivascular pattern and many thin-walled branching staghorn vessels (H&E, ×200). ... MPC is a rare, recently delineated tumor that originates from the perivascular myoid cells1. It was described by Granter et al.2 in 1998 and newly entered into a subgroup of perivascular tumors in the World Health Organization classification of soft tissue tumors3. MPCs are well-circumscribed and composed of a mixture of solid cellular areas intermixed with variable numbers of vascular channels. The latter are often elongated and display prominent branching, resulting in a stag-horn appearance. The cells in the solid areas are round, or short and spindle shaped with eosinophilic cytoplasm and vesicular nuclei. The presence of concentric layers of tumor cells around vascular channels resulting in a typical onion ring appearance is a hall mark of this tumor2. However, MPC tumors exhibits a broad spectrum of growth patterns: solid classic, hemangiopericytoma-like, angioleiomyoma-like, hypocellular fibroma-like, solitary fibrous tumor-like, glomus tumor-like, cellular immature, intravascular and malignant subtypes. The present case was classified as angioleiomyoma-like pattern. By immunohistochemistry, the neoplastic cells characteristically express muscle-specific actin, smooth muscle actin and h-caldesmon, and are negative for CD34 and desmin4. The differential diagnosis includes myofibroma/myofibromatosis, angioleiomyoma, or glomus tumors. Myofibroma/myofibromatosis shows a distinct biphasic pattern consisting of fascicles of spindle cells and immature appearing zones2. Although perivascular concentric growth pattern has been observed in a subset of angioleiomyoma, this is not the predominant histopathologic feature, and angioleiomyomas show positive reaction for desmin in the smooth muscle bundles. In contrast, MPC is usually negative or only focally positive for desmin5. Glomus tumors can be distinguished by tumor cells showing more abundant eosinophilic cytoplasm and distinct cell borders. In addition, glomus tumors lack the concentric orientations of tumor cells around vessels characteristic of MPC4. MPCs typically arise in subcutaneous tissue as single or multiple nodules on the extremities of adults, with only rare cases of multicentricity. MPC presents as a benign, slow-growing nodule, and may occasionally be painful. Tumors rarely exceed 2 cm in size. A rare malignant transformation has been reported as well5. Most MPCs do not recur following excision4. Our patient decided to leave her lesion untreated. Involvement of the face in MPC cases is previously undescribed in the Korean dermatologic literature. Presentation of this case of MPC on the cheek will aid others in recognizing this very rare entity.

Multiple Myopericytoma of the Face and Parotid Gland

Myopericytoma is a benign tumor that is composed of myoid-appearing oval to spindle-shaped cells with a concentric perivascular pattern of growth. The tumor is morphologically heterogeneous and can exhibit a broad histologic spectrum. We describe a case of multiple myopericytoma occurring in the head and neck skin region with involvement of the parotid gland where it is known to occur very rarely. A 40-year-old woman noticed multiple enlarging, painless, round-shaped masses on her left cheek. The patient had experienced a similar lesion of the same area 8 years earlier which was completely excised and the pathological diagnosis was spindle cell type myoepithelioma. On a computed tomographic image, one mass involved the superficial parotid gland and was well encapsulated. Excision of the facial masses and superficial parotidectomy with facial nerve preservation were performed. A diagnosis of myopericytoma was established in light of the immunohistochemical pattern with the histopathological findings. Over the 4-year follow-up period, there was no evidence of recurrence. As many perivascular myoid neoplasms share common morphologic features with myopericytoma, we should consider the differential diagnosis, and confirm the histological findings with appropriate immunohistochemical staining. After identifying myopericytoma, it should be treated with wide surgical excision to prevent local recurrence.

Myopericytoma of the lip: Report of case

Myopericytoma is a recently delineated entity showing a hemangiopericytoma-like vascular pattern. This rare mesenchymal neoplasm arises within the subcutaneous tissue of the extremities. Only 3 cases of myopericytoma involving the soft tissues of the mouth have been reported, and this case is the first, to the best of our knowledge, that involves the lips. A 28-year-old black man had a slowly growing, painless, firm, ulcerated lower lip mass. Histopathologic examination and immunohistochemical analysis were performed, and the differential diagnosis included carcinoma and other well-circumscribed, vascular, slow-growing lesions of the mouth-like myofibroma, glomus tumor, and solitary fibrous tumor. The results of the histology combined with the immunohistochemical analysis led to a diagnosis of myopericytoma. This case may aid others in recognizing this very rare entity. As the myopericytoma shares morphologic features with other perivascular myoid neoplasms, it should be included in the differential diagnosis of well-circumscribed, vascular, slow-growing lesions of the mouth.

Primary perivascular epithelioid cell tumor of the liver not related to hepatic ligaments: hepatic PEComa as an emerging entity.

Primary perivascular epithelioid cell tumor (PEComa) of the liver is a very rare example of an emerging family of hepatic PEC tumors. Only few cases have been described so far. We report the case of a large but benign hepatic PEComa in a 53-year-old man without signs of tuberous sclerosis. In contrast to recently described PEC-derived liver tumors in children and young adults, this neoplasm was not related to the hepatic ligaments but had developed deeply within the liver substance. The neoplastic cells displayed the complete phenotype typical for PEComas, i.e. reactivity for several melanoma markers and for smooth muscle actin. The unique relationship of myoid tumor cells to the adventitia of blood vessels prompted us, in comparison with published findings obtained with angiomyolipomas, to comment on the possible origin of the still enigmatic perivascular epithelioid cells.

Myopericytoma: report of two cases associated with trauma

Myopericytoma is a rare, recently described tumor demonstrating a hemangiopericytoma-like vascular pattern. We present two cases of myopericytoma associated with trauma: a 64-year-old man who developed several nodules on his nose four months after sustaining multiple abrasions to his forehead and nose, and a 72-year-old woman with a solitary growth in the alveolar ridge of unknown duration. Biopsy specimens of the lesions in both cases demonstrated a striking concentric perivascular proliferation of bland spindle-shaped pericytic cells characteristic of myopericytoma. Despite sharing morphologic features with angioleiomyoma, myofibroma and glomus tumor, myopericytoma is thought to represent a distinct perivascular myoid neoplasm of skin and soft tissues. The tumor is characterized by a radial and perivascular arrangement of ovoid, spindled to round neoplastic cells that are immunoreactive to alpha-smooth muscle actin, often for h-caldesmon as well as smooth muscle myosin-heavy chain, and usually negative for desmin antibodies. Most cases of myopericytoma are benign, however, local recurrence and malignancy have recently been reported, Myopericytoma can be multifocal involving a single or multiple anatomic regions, and tends to occur in dermal and superficial soft tissues of adults primarily on the extremities. Our cases are unusual examples of myopericytoma manifesting as multiple nodules on the nose, and a solitary growth on the buccal mucosa after trauma.

Perivascular myoid tumors of the oral region: a clinicopathologic re‐evaluation of 35 cases

Myopericytoma (MPC) is a generic denomination to describe tumors showing differentiation toward perivascular myoid cells /myopericytes. It has been suggested that MPC forms a morphologic continuum with glomus tumor (GT), solitary myofibroma (SMF), and angioleiomyoma (ALM). This proposed relationship has not yet been assessed in the oral region. We reviewed our 28-year experience with 35 oral tumors, originally diagnosed as ALM (n = 28), SMF (n = 4), GT (n = 2), and MPC (n = 1) to analyze their overlapping microscopic features, with the assistance of immunohistochemistry. Myopericytoma showed a wide range of growth patterns; concentric perivascular whorls, hemangiopericytomatous areas, glomangiopericytoma (GPC)-type vessels and leiomyomatous foci. Intravascular growth was also seen. Among 28 cases studied, three ALM were reclassified as MPC (n = 2) and SMF (n = 1), based on the present diagnostic criteria. Additional MPC-type components, at varying degrees, were similarly found in four ALM and three SMF, at least focally. One GT featured intravascular whorls of spindle cells. These four interrelated groups of tumors had in common GPC-type vasculature and intraluminal cellular proliferation was nearly ubiquitously present. Diffuse immunoreactivity for alpha-smooth muscle actin and less staining intensity of muscle-specific actin were observed in all tumors. Only ALM displayed desmin positivity of variable extent. Neither case tested expressed CD34. Our data matches with the recent results in extraoral sites that MPC, GT, SMF, and ALM exhibit histologic and immunohistochemical overlap with each other. A common perivascular myoid differentiation between these tumor types is further reinforced by the present oral series.

Myopericytoma of Skin and Soft Tissues

Perivascular neoplasms comprise traditionally glomus tumor and hemangiopericytoma (HPC). Whereas glomus tumor represents a well-defined entity, the existence of HPC as a separate entity has been questioned because a number of neoplasms of different lines of differentiation are characterized by a HPC-like vascular growth pattern. Myopericytoma represents a recently delineated entity showing a HPC-like vascular pattern. A large series of myopericytoma of skin and soft tissues has been analyzed to further characterize the clinicopathologic spectrum of this entity. Fifty-four cases of myopericytoma of skin and soft tissues were retrieved and the histology reviewed. Immunohistochemical stainings using alpha-smooth muscle actin (ASMA), desmin, and h-caldesmon antibodies were performed, and clinical data and follow-up information were obtained from referring pathologists. Thirty-four patients were male and 18 were female (gender was unknown in 2 cases). Patient age ranged from 13 to 87 years (median, 52 years). The lower extremities were most commonly affected (26 cases) followed by the upper extremities (16 cases), the head and neck region (4 cases), and the trunk (2 cases); exact location was unknown in 5 cases. In 20 cases, the neoplasms were confined to the dermis, in 6 cases an extension into the subcutis was seen, and 24 as well as 4 cases arose in subcutaneous and deep soft tissue, respectively. Two cases were multicentric; and in 1 of these patients, multiple anatomic regions were involved. Histologically, in all cases, numerous thin-walled vessels and a concentric, perivascular arrangement of ovoid, plump spindled to round myoid tumor cells was seen. However, a broad morphologic spectrum ranging from hypocellular, fibroma-like (3 cases), myofibroma-like (2 cases), angioleiomyoma-like (12 cases), and HPC-like neoplasms (13 cases) to classic myopericytomas (14 cases) and immature, cellular lesions (2 cases) was noted. In addition, 2 neoplasms with focal glomoid features, 5 intravascular, and 1 malignant myopericytomas were found. Prominent cytologic atypia and increased proliferative activity (>3 mitoses/10 high power fields) was seen in 4 and 2 cases, respectively. Immunohistochemically, all cases tested stained positively for ASMA. In addition, 29 of 32 cases tested stained positively for h-caldesmon, whereas desmin was only focally positive in 3 of 33 cases. Follow-up information was available in 46 cases (range, 7-168 months; median, 48 months). Despite marginal or incomplete excision in 23 of 46 cases, only 2 neoplasms (1 malignant and 1 intravascular myopericytoma) recurred locally (within 1 and 4 years, respectively). Despite overlapping morphologic features to angioleiomyoma and myofibroma, myopericytoma represents a distinct perivascular, myoid neoplasm of skin and soft tissues, characterized by a broad morphologic spectrum of concentrically, perivascularly growing myoid tumor cells that stain positively for ASMA and often for h-caldesmon, whereas desmin is usually negative. Most cases of myopericytoma behave in a benign fashion, but local recurrences and rarely metastases may occur in atypical and malignant neoplasms.

Myoid differentiation and prognosis in adult pleomorphic sarcomas of the extremity: an analysis of 92 cases.

The results of a recent study demonstrated an association between myoid differentiation and an adverse prognosis in adult patients with pleomorphic sarcoma, as determined by 5-year metastasis-free survival rates. To confirm the importance of muscle differentiation on prognosis in a well controlled clinical context, 92 samples from patients with pleomorphic sarcoma of the extremity from a single institution were immunostained with 4 monoclonal antibodies believed to be correlated with myoid differentiation: alpha-smooth muscle actin, muscle-specific actin, desmin, and myoglobin. Forty-two cases were positive for at least 1 muscle marker and 50 cases were uniformly negative. Between the two groups, there was no significant difference in tumor size, tumor extent, or patient age found; however, histologic grade was significantly higher (P = 0.038) in the myoid tumors. The 5-year survival differed significantly between patients with myoid tumors (35%) and those without myoid tumors (65%) (P = 0.0054). Myoid differentiation remained an adverse prognostic indicator after adjusting for clinically significant factors (i.e., histologic grade, tumor size, tumor extent, and patient age) (P = 0.01) (hazard ratio, 2.39; 95% confidence interval, 1.24-4.63). Furthermore, there was an inverse relation found between the number of myoid markers present and survival (P = 0.004). Myoid differentiation was found to be an independent indicator of adverse prognosis in adult patients with pleomorphic spindle cell sarcoma of the extremity.

Pseudosarcomatous myofibroblastic tumor and myosarcoma of the urogenital tract.

Abstract Objective.—Pseudosarcomatous myofibroblastic tumors (PMTs) of the urogenital tract are rare but distinctive lesions. Despite their benign behavior, they are frequently misinterpreted as leiomyosarcomas and rhabdomyosarcomas in preoperative biopsies and even in resected specimens because of their atypical spindle-cell features. Precise diagnosis of PMTs is important to avoid unnecessary radical therapy. We analyzed urogenital myoid tumors to clarify which of their characteristics are useful for the differential diagnosis. Methods.—We evaluated 7 urogenital myoid tumors consisting of 3 PMTs, 2 leiomyosarcomas, and 2 rhabdomyosarcomas. We studied the expression of various immunohistochemical muscle-cell markers including desmin, muscle-specific actin, α-smooth muscle actin, high-molecular-weight caldesmon, and myogenin. Results.—Desmin, muscle-specific actin, and α-smooth muscle actin were noted variably in all tumor types, whereas high-molecular-weight caldesmon was expressed only in leiomyosarcoma...