CD34‐positive infantile myofibromatosis: Case report and review of hemangiopericytoma‐like pattern tumors

We describe a case of CD34‐positive infantile myofibromatosis with hemangiopericytoma‐like pattern. A 2‐day‐old Japanese boy presented with multiple hemispherical nodules on the extremities and back. There was a biphasic histological growth in the dermis, accompanied by a hemangiopericytoma‐like pattern with antler‐like branching vessels. Tumor cells were oval to spindle‐shaped myoid cells with bland appearance. Immunohistochemically, vimentin, calponin and CD34 were positive, while α‐smooth muscle actin, h‐caldesmon, HHF35 and desmin were negative. Although CD34 was positive, the present case could be diagnosed as infantile myofibromatosis. Myopericytoma, myofibroma/myofibromatosis, glomus tumor, glomangiopericytoma and angioleiomyoma share a continuous spectrum of benign hemangiopericytoma‐like pattern tumors. Myofibroma/myofibromatosis is nearly included in myopericytoma among pericytic (perivascular) tumors, and could be positive for CD34. Several immunohistochemical panels of smooth muscle markers are needed for the diagnosis of pericytic (perivascular) tumors.     

Myopericytoma proliferating in an unusual anastomosing multinodular fashion

We herein describe a case of myopericytoma that proliferated in an unusual fashion. Myopericytoma is described as a group of rare, benign, dermal or subcutaneous tumors that are characterized histologically by a striking, concentric, perivascular proliferation of spindle cells and showing apparent differentiation towards perivascular myoid cells. Myopericytoma forms a morphological continuum with myofibroma/myofibromatosis, glomus tumor and angioleiomyoma. The patient was a 64‐year‐old woman who demonstrated a recurrent ulcer on an atrophic plaque on her left shin. A histopathological examination of the plaque demonstrated that tumor cells proliferated in an anastomosing multinodular fashion along the vessels in the dermis and subcutaneous tissue. In those nodules, there were numerous, small, concentric proliferations of myoid‐appearing spindle cells around small vascular lumina. The present case is an unusual example of myopericytoma, manifesting in a characteristic anastomosing, multinodular, infiltrating fashion.     

Adult cutaneous myofibroma

A 63-year-old male presented with an asymptomatic, slow-growing swelling on the right lower limb for the past one and half years. The histopathology revealed a lobular neoplasm with a biphasic pattern of spindle shaped cells and hemangiopericytoma like areas at the periphery of the lobule. The diagnosis of adult cutaneous myofibroma was made. This case highlights the importance of histopathology in reaching a definitive diagnosis.     

Intravascular myopericytoma

BACKGROUND: Myopericytoma is a benign tumor composed of cells that show apparent differentiation towards putative perivascular myoid cells called myopericytes. It arises most commonly in the dermis or subcutaneous tissue of the extremities in adults. METHODS: We describe a myopericytoma that was unusual in its intravascular location. RESULTS: A 54-year-old man presented with a 10-year history of a painful slowly growing 1.5-cm nodule in the subcutaneous tissue of the thigh. Histologic examination of the excised lesion showed that is was entirely contained within the lumen of a vein. It was composed of a proliferation of myoid-appearing spindle cells, which were arranged in a striking concentric pattern around numerous blood vessels, in a manner that accentuated the vessel walls. This pattern is characteristic of myopericytoma. In some areas, fascicles of spindle cells, embedded in a myxoid stroma, bulged into the lumina of lesional vessels, reminiscent of myofibroma/myofibromatosis. Lesional spindle cells were diffusely positive for smooth muscle actin, focally positive for CD34 and were negative for desmin, cytokeratin, S100 protein, HMB-45 and CD31. CONCLUSION: This case illustrates that myopericytoma can be entirely intravascular in its location.     

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.     

Myoid differentiation in dermatofibrosarcoma protuberans and its fibrosarcomatous variant: clinicopathologic analysis of 5 cases

We report a series of five cases of dermatofibrosarcoma protuberans, four of which were fibrosarcomatous and all of which showed histologic and immunohistochemical evidence of focal myoid/myofibroblastic differentiation (accounting for up to 5% of each tumor). These lesions were identified amongst 208 cases of dermatofibrosarcoma protuberans including 24 examples of the fibrosarcomatous variant. Three of the five patients were male and two were females; all were adults (37–72 years). One case arose on the scalp and two cases each on the abdominal wall and upper trunk. All tumors were less than 5cm in diameter and preoperative duration ranged from 2 months to 10 years. In three cases with follow-up there was no recurrence. Histologically, all tumors were typical fibrosarcomatous or ordinary dermatofibrosarcoma protuberans but for the presence of scattered to confluent nodules and bundles of eosinophilic spindle cells associated with well-defined cytoplasmic margins and vesicular nuclei associated with focal stromal hyalinization. While the typical dermatofibrosarcoma protuberans areas were CD34 positive, the myoid areas were negative for this antibody and positive for smooth muscle actin and pan-muscle actin. All tumors were desmin negative. Recognition of myofibroblastic differentiation in fibrosarcomatous dermatofibrosarcoma protuberans is important not only because it gives support to the theory of a fibroblastic/myofibroblastic line of differentiation for this type of tumor, but also because it might be a source of confusion with other myofibroblastic lesions (e.g. myofibromatosis, adult myofibroma), especially when small biopsies are evaluated.     

Cutaneous adult myofibroma: a vascular neoplasm

Infantile myofibromatosis is a distinctive type of fibromatosis that usually develops during the immediate perinatal period. There are variants with solitary and multiple tumors. Lesions confined to the skin, soft tissue, and bone carry a good prognosis, showing spontaneous regression. The prognosis, however, is much less favorable when visceral lesions are present and the outcome may be fatal. Only recently it became obvious that there is an adult counterpart of infantile myofibromatosis, characterized by solitary lesions that have a predilection for involve the dermis and show no tendency to regression, although they have an entirely benign biological behavior. These lesions have been named cutaneous myofibroma or solitary myofibroma of adults. We have studied the clinical, histopathological and immunohistochemical characteristics of 53 examples of cutaneous adult myofibroma. In addition, 2 cases were examined ultrastructurally. The patients were mostly adults with ages ranging from 6-83 years. The lesions presented as solitary, usually painless nodules of variable duration on the skin, usually located on the extremities. Histopathologically, four patterns were identified: nodular or cellular type, multinodular or biphasic type, leiomyoma-like or fascicular type, and vascular type. A correlation between the histopathologic pattern and the lesional age was observed: vascular type of cutaneous adult myofibroma in early lesions, nodular and multinodular lesions in fully developed lesions, and leiomyoma-like or fascicular type in late lesions. Immunohistochemically, the spindle cells were desmin negative, but expressed immunoreactivity for vimentin, pan-smooth muscle actin, and alpha-smooth muscle actin. Ultrastructurally, neoplastic cells showed characteristics of undifferenciated mesenchymal cells with features of fibroblasts, myofibroblasts and pericytes. Primitive vascular formations were seen in the form of irregular clefts between adjoining cells. We conclude that cutaneous adult myofibroma is a little-known benign vascular neoplasm probably derived from myopericytes.     

Myoid differentiation and EMA expression in fibrosarcomatous dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a relatively unusual, locally aggressive cutaneous tumor of intermediate malignancy. Fibrosarcomatous DFSP (FS-DFSP), a rare variant of DFSP, has a higher tendency for recurrence and metastasis. Recently, a small number of cases of another variant of FSDFSB characterized by areas of myoid differentiation have been reported. We present here a 35 yearold female patient with myoid differentiation in FS-DFSP. The tumor on the left scapular region had slowly grown over six years. Examination revealed a domeshaped, firm, nontender, violaceous dermal nodule. Histologically, it was composed of a monotonous spindle cell population arranged predominantly in a storiform pattern and to a lesser extent in a fascicular fibrosarcomatous pattern with a parallel arrangement of the cells. Immunohistochemically, the tumor cells showed diffuse expression for vimentin and CD34. In the center of the tumor areas with frequent mitosis, hypercellular and negative reactive for CD34 were seen. In addition, approximately 10% of the cells were positive for epithelial membrane antigen. Myoid differentiation was found around the blood vessels. The myoid areas were positive for smooth muscle actin and negative for desmin. It is possible that the presence of hyperplastic myofibroblasts is a reactive phenomenon to the proliferation of tumor cells. We believe that this finding around blood vessels may be present in DFSP or FS-DFSP. However, when myoid areas, myoid fascicles and myoid nodules are seen in the stroma, it may be a new morphological variant of DFSP and/or FS-DFSP.     

An ultrastructural and immunohistochemical study of pigmented dermatofibrosarcoma protuberans (Bednar tumor).

A case of Bednar tumor on the right shoulder of a 47-year-old Japanese woman is reported. Histological examination showed plump, spindle cells arranged in a storiform pattern in central areas of the tumor and a diffuse infiltration of the dermal stroma, which was frequently extended into the subcutis at the periphery of the tumor. The tumor contained a fairly identified population of dendritic pigmented cells. Ultrastructurally, most cells had folded nuclei, were spindle-shaped and had long, slender cytoplasmic projections. Dendritic pigmented cells, which were dispersed among neoplastic cells, contained premelanosomes and mature melanosomes. Immunohistochemically, tumor cells exhibited positive reactions for vimentin and CD 34 and failed to show a positive reaction for neuron specific enolase, HMB-45 or S-100 protein. Factor X IIIa was only expressed on tumor cells around melanin-containing cells, which reacted positively with antibodies to S-100 protein and vimentin. These results indicate that the phenotype of tumor cells around melanin-containing cells differs from other tumor cells and that this difference may be caused by the relationship of tumor cells and melanin-containing cells.     

Hemangiopericytoma-like dermatofibroma with mast cells

We report an unusual case of hemangiopericytoma-like dermatofibroma in the right shoulder of an 82-year-old patient with a well-defined nodular growth located in the dermis. Microscopic study revealed a band of haphazardly arranged cells with a vascular component of gaping, simple, endothelial-lined vascular structures with intervening postcapillary venules and capillary-sized slit-like "staghorn" vascular channels filled with erythrocytes; abundant mast cells were also observed. The neoplasm cells were positive for CD68 and Factor XIIIA and negative for CD34. Few data have been published on the presence of abundant mast cells (tryptase and CD117 positive) in these neoplasm. The differential diagnosis of this entity should consider other spindle cell neoplasm, including hemangiopericytoma/solitary fibrous tumor, dermatofibrosarcoma protuberans, myopericytoma, angioleiomyoma, amelanotic melanoma, pecoma, and benign and malignant peripheral nerve tumors. We present an infrequent case of dermatofibroma with a vascular pattern resembling hemangiopericytoma and the presence of abundant mast cells, which may be responsible for this vascular component.     

Eruptive dermal clear cell desmo‐plastic mesenchymal tumors with perivascular myoid differentiation in a young boy. A clinical,histopathologic, immunohistochemical and electron microscopy study of 17 lesions

Clear cell tumors of the skin are observed in a wide variety of benign and malignant conditions with different histogenesis, sharing the presence of cells with abundant clear cytoplasm. Herein, we report the clinicopathologic features of a healthy young patient affected by asymptomatic, eruptive and disseminated, benign clear cell dermal tumors since early infancy. Neither family history nor genetic testing and counseling provided further useful information. The lesions were mostly confined to the face and lower left extremity with pink teleangiectatic papules and small nodules. Over a 4‐year period, a total of 16 different cutaneous lesions were biopsied and histopathologic and immunohistochemical studies carried out; an additional lesion was also removed for electron microscopy examination. Histopathology evidenced multiple perivascular growths of spindle to oval and round cells intermingled with clear/granular cells throughout the dermis, with prominent desmoplasia and numerous capillary‐like vessels with focal hemangiopericytoma‐like features. Immunohistochemical neoplastic cells were uniformly positive for h‐caldesmon and focally smooth muscle α‐actin and CD13 indicating myoid differentiation whereas the consistent diffuse cytoplasmic staining for lysosome antigen, such as CD68PG‐M1 and NKI/C3 along with the ultrastructural findings supported the view of a lysosome‐mediated apoptotic process. The differential diagnosis with other clear cell cutaneous neoplasms is discussed.     

Perivascular myoma of myopericytoma and myofibromatosis-type arising in a chronic scar

We describe a case of a cutaneous perivascular myoma with features overlapping between the myofibromatosis and the myopericytoma type. The patient is a 58-year-old woman with a painless plaque-like and multinodular lesion in the pretibial dermis and subcutaneous tissue. She had repeated trauma to this site, first in her early youth that left an area of hyperpigmentation, and then again at age 40. The biopsy showed a biphasic pattern with a myofibromatosis-type component composed of spindle cell myoid nodules and more cellular round cell areas. The myopericytoma-like areas appeared to be infiltrating along vessels. These areas contained aggregates of immature-appearing cells arranged concentrically around vascular lumina in a manner reminiscent of pericytes. Immunohistochemical stains showed focal positivity for smooth muscle actin. Immunohistochemical and ultrastructural studies have showed these pericyte-like cells to be of a myoid origin. The reason for the neoplastic proliferation of perivascular myoid cells is presently unknown. The association of trauma and neoplastic transformation of the skin is rare. We report the first case of a cutaneous perivascular myoma arising in a chronic scar.     

Scanning electron microscopic features of Kaposi's sarcoma

In order to clarify the three-dimensional structure of Kaposi's sarcoma (KS) five cases of KS of the skin were observed with a scanning electron microscope (SEM). KS lesions were investigated both in vascular and spindle cell areas and were compared with similar areas observed by light microscopy. KS appears as a spongelike neoplasm consisting of irregular vascular channels lacking endothelial cells and well-developed basement membranes. Vascular spaces and vascular slits are packed with numerous red blood cells (RBCs). SEM features of KS share some similarities with those of hemangiopericytoma, a vascular tumor composed of mature endothelial cells surrounded by pericytes. These findings are consistent with the hypothesis according to which the proliferating cells of KS are viewed as immature endothelial cells with partial differentiation into pericytes.     

Kaposi sarcoma following postmastectomy lymphedema

Classical Kaposi sarcoma (KS) usually appears on lower extremities accompanied or preceded by local lymphedema. However, the development in areas of chronic lymphedema of the arms following mastectomy, mimicking a Stewart–Treves syndrome, has rarely been described. We report an 81‐year‐old woman who developed multiple, erythematous to purple tumors, located on areas of post mastectomy lymphedema. Histopathological examination evidenced several dermal nodules formed by spindle‐shaped cells that delimitated slit‐like vascular spaces with some red cell extravasation. Immunohistochemically, the human herpesvirus type 8 (HHV‐8) latent nuclear antigen‐1 was detected in the nuclei of most tumoral cells confirming the diagnosis of KS. Lymphedema could promote the development of certain tumors by altering immunocompetence. Although angiosarcoma (AS) is the most frequent neoplasia arising in the setting of chronic lymphedema, other tumors such as benign lymphangiomatous papules (BLAP) or KS can also develop in lymphedematous limbs. It is important to establish the difference between AS and KS because their prognosis and treatment are very different. Identification by immunohistochemistry of HHV‐8 is useful for the distinction between KS and AS or BLAP.     

h-Caldesmon as a specific marker of smooth muscle cell differentiation in some soft tissue tumors of the skin

BACKGROUND: An existing problem in contemporary pathology is the classification and distinction of spindle cell soft tissue tumors of the skin. Markers such as alpha-smooth muscle actin (alpha-SMA) and desmin, considered specific for smooth muscle cell (SMC), have been shown to be expressed in a variety of fibroblastic and myofibroblastic processes. High-molecular-weight caldesmon (h-caldesmon), one of two isoforms, is reported to be expressed exclusively by SMC and has recently been shown to be a specific marker of SMC tumors. METHODS: Tumors were obtained from 11 patients taken from the surgical pathology archives of the University of South Florida and cases were coded as smooth muscle hamartoma, myofibroma, and dermatomyofibroma. RESULTS: The case of smooth muscle hamartoma had greater than 90% of tumor cells labeling with anti-h-caldesmon antibodies. Three of three cases of myofibroma had focal areas of positivity representing less than 10% of total tumor cells. Seven of seven dermatomyofibromas showed no apparent labeling with anti-h-caldesmon antibody. Dense reactivity was noted in vascular wall smooth muscle, indicating internal controls. CONCLUSIONS: We can conclude that h-caldesmon is a specific marker of fully differentiated smooth muscle and that it can serve to differentiate spindled SMC soft tissue tumors of the skin from tumors of myofibroblastic and/or fibroblastic origin.     

Atypisches Fibroxanthom – eine nicht‐„histiozytäre” Neoplasie.

Summary: On account of the controversial histogenesis of atypical fibroxanthoma (AFX) we examined 9 typical cases of this tumor histologically and by immunohistochemistry. Histology revealed eroded, ill‐defined dermal lesions with a pleomorph‐storiform growth pattern, predominantly composed of pleomorphic cells with numerous, in part atypical mitoses and variably accompanied by monomorphous cells among them also spindle cell areas. Three of our specimens contained osteoclast‐like giant cells. Immunohistologically, lesions consistently expressed vimentin, focally in histological monomorphous spindle areas alpha smooth muscle actin and reacted focally with KP1 and stronger with Ki‐M1p also in histologically bland areas without atypia and mitoses, but were generally negative for keratin, desmin and S‐100 protein. The average Ki‐M1p positivity accounted for 10 – 20 % of cells, in single cases focally up to 60 %. In order to investigate the nature of this cell population, sections were co‐labeled with the proliferation marker MIB1. MIB1 positivity accounted for up to 40 % of cells, yet only very occasional ones exhibited double staining with Ki‐M1p. Osteoclast‐like giant cells reacted with macrophage markers KP1 and Ki‐M1p, but not with MIB1. Thus, a macrophage differentiation of AFX appears to be excluded and the in part strong reactivity pattern for Ki‐M1p should best be regarded as an inflammatory background reaction against a neoplastic tissue destruction.     

Adult acral cutaneous myofibromas in a patient with generalized morphea

Myofibroma is the term for a group of solitary or generalized soft tissue tumors that may be located in the skin or within skeletal muscle, bone, and viscera. These tumors occur most commonly in children. However, examples of myofibroma have been reported in adults, in whom they usually present as solitary lesions of the head and neck, trunk, and extremities. "Cutaneous nodules" have been reported in both localized and systemic scleroderma, but to our knowledge, there are no specific reports of myofibromas developing in this patient population. We report a case of acral myofibromas in a patient with generalized cutaneous morphea. This occurrence is of interest in view of the possible role of myofibroblasts in the pathogenesis of scleroderma.