Granular Cell Tumor of the Eye (Myoblastoma): Ultrastructural and Immunohistochemical Studies

The clinical and pathological characteristics of a myoblastoma of the orbital are described. The tumor presented as a painless hard mass in the left orbit of a 56-year-old caucasian male, causing diplopia and hypertrophy of the left eye in the primary visual position. Light microscopy studies revealed a typical granular cell tumor with PAS-positive intracytoplasmic granules. Immunoperoxidase studies showed positivity for S-100 protein and desmin. Electron microscopy studies showed numerous intracellular myelin degenerative bodies. The patient developed an epidermoid cyst at the site of initial surgery, but has no signs of local or distant disease two years after initial treatment.

[Clinicopathologic study of sinonasal inflammatory myofibroblastic tumor]

OBJECTIVE

To study the clinicopathologic features, immunophenotype and ultrastructural features of sinonasal inflammatory myofibroblastic tumors (IMT).

METHODS

The clinical and histologic features of 5 cases of sinonasal IMT were reviewed. Immunohistochemical study for vimentin, MSA, SMA, calponin, h-caldesmon, desmin, ALK, fibronectin, CK, S-100 and Ki-67 was carried out. Ultrastructural examination was also performed in two of the cases.

RESULTS

The patients age ranged from 28 to 62 years (mean = 43 years). The male-to-female ratio was 2:3. The clinical presentation included nasal obstruction, nasal discharge, nasal bleeding, facial pain, facial swelling, toothache and tear overflow. All of the 5 patients suffered from disease relapses; and 4 of them had recurrences for more than 5 times. One patient had lymph node metastasis and 3 patients died of the disease. Histologically, the tumor cells were arranged in interlacing fascicles and sometimes haphazard in fashion. They were spindly in shape, cytoplasm eosinophilic with mild nuclear atypia and a low mitotic activity. The intervening stroma was myxoid in appearance accompanied by lymphocyte and plasma cell infiltration, abundant blood vessels and focal collagenized areas. In 3 of the recurrent cases, the tumor cells displayed increased nuclear atypia and mitotic activity (average about 5 to 6 per 10 high-power fields), accompanied by patchy necrosis, less inflammatory cell infiltration and focal sarcomatous changes. Immunohistochemical study showed that the tumor cells were diffusely positive for vimentin. SMA, MSA, calponin and fibronectin were variably expressed. Desmin was weakly positive in 1 case. The staining for h-caldesmon, ALK, S-100 and CK was negative. The Ki-67 proliferation index increased with tumor recurrences. Electron microscopy revealed abundant rough endoplasmic reticulum and dense body formation in the cytoplasm. There were an increased amount of collagen fibers in the stroma.

CONCLUSIONS

IMT rarely occurs in nasal cavity and paranasal sinuses. The tumor is prone to local invasion and recurrences, with subsequent progression to frank malignancy and distant metastasis, resulting in high mortality and poor prognosis. Complete surgical resection remains the main modality of treatment.

The Spectrum of Pediatric Fibroblastic and Myofibroblastic Tumors

Fibroblastic and myofibroblastic tumors in neonates, infants, and children provide a diagnostic dilemma in surgical pathology due to their relative rarity and similarity in appearances. These tumors may be congenital or occur early during the first years of life or later during the first and second decades of life. The morphologic, immunocytochemical, ultrastructural, cytogenetic, and molecular features of the more "common" pediatric fibroblastic and myofibroblastic tumors are reviewed. In addition, the importance of a multimodal approach to tumor diagnosis is emphasized, with correlation with treatment and outcome differences among these unique fibroblastic and myofibroblastic tumors. The importance of providing an accurate diagnosis with pediatric fibroblastic and myofibroblastic tumors cannot be overstated, because treatment, prognosis, follow-up, and outcome are based on the initial assessment of these fascinating, but oftentimes, perplexing tumors.

Angiomyofibroblastoma-like tumor (cellular angiofibroma) in the male inguinal region

Angiomyofibroblastoma-like tumor is a rare mesenchymal tumor involving the male genital tract. We report a case of an angiomyofibroblastoma-like tumor that arose in the subcutaneous tissue of the left inguinal region in a 50-year-old man. Ultrasonography of the region demonstrated a well-circumscribed subcutaneous mass. Intralesional fat was revealed on magnetic resonance images. Although these imaging features are nonspecific, radiological findings enable considering the diagnosis of angiomyofibroblastoma-like tumor.

The myofibroblast: a study of normal, reactive and neoplastic tissues, with an emphasis on ultrastructure. part 2 - tumours and tumour-like lesions

This paper describes the ultrastructure of the commoner myofibroblastic tumours and tumour-like lesions. The objective is to complement mainstream pathology texts, which have concentrated on the clinical and light microscopy features of these lesions and which have arguably but understandably somewhat neglected electron microscopy as an ancillary diagnostic tool and a technique for investigating tumour cell biology. Ultrastructural features are described of nodular fasciitis, the myofibromatoses (including Dupuytren's disease), inflammatory myofibroblastic tumour, post-operative spindle cell nodule, fibroma of tendon sheath, fibrous pseudotumour, benign fibrous histiocytoma, atypical fibroxanthoma, dermatofibrosarcoma protuberans, myofibrosarcoma (myofibroblastic sarcoma), malignant fibrous histiocytoma (pleomorphic myofibrosarcoma), epithelioid sarcoma and spindle-cell carcinoma. Fibrosarcoma and leiomyosarcoma are illustrated for comparison. The fibronexus is emphasised as an important marker for the most confident diagnosis of myofibrosarcoma. Some pathologists accept a light microscope definition, which includes alpha-smooth-muscle actin positivity, h-caldesmon negativity and, in some cases, desmin positivity. Caution in the interpretation of desmin staining in a possible myofibroblastic lesion is urged, since, in combination with an ultrastructurally identified lamina, it more probably suggests true smooth-muscle differentiation. Myofibroblastoma and angiomyofibroblastoma are examples of tumours argued on the basis of ultrastructural findings (sometimes in combination with desmin staining) to be primitively differentiated smooth-muscle cell rather than myofibroblastic proliferations.

Low-grade sarcomas with CD34-positive fibroblasts and low-grade myofibroblastic sarcomas

A subset of low-grade fibrosarcomas is composed of CD34-positive spindle cells. These include dermatofibrosarcoma, its morphologic variants, and its associated fibrosarcoma, solitary fibrous tumor, hemangiopericytoma and their malignant counterparts, and some cases of myxoinflammatory fibroblastic sarcoma. Dermatofibrosarcoma and related lesions are characterized by a t(17;22)(q22;q13) rearrangement resulting in fusion of the genes COL1A (17q21-22) and PDGFB1 (22q13). Solitary fibrous tumor displays varying cellularity and fibrosis and a peripheral hemangiopericytomatous pattern; most tumors formerly called hemangiopericytoma are now subsumed into the category of solitary fibrous tumor, although a few strictly defined examples are recognized; however, these are probably not composed of pericytes. Myofibroblastic malignancies are best identified by electron microscopy, with which varying degrees of differentiation, including the presence of fibronexus junctions, can be identified. Low-grade sarcomas showing myofibroblastic differentiation include myofibrosarcomas and inflammatory myofibroblastic tumors. Myofibrosarcomas are spindle cell neoplasms that occur in children or adults in the head and neck, trunk, and extremities as infiltrative neoplasms and that display a fascicular or fasciitis-like pattern with focal nuclear atypia and variable expression of myoid antigens. These sarcomas are prone to recurrence and a small number metastasize. Inflammatory myofibroblastic tumor (synonymous with inflammatory fibrosarcoma) is a neoplasm arising predominantly in childhood, and frequently in intraabdominal locations. It has spindle cells in fascicular, fasciitis-like and sclerosing patterns, with heavy chronic inflammation including abundant plasma cells. Many IMT have clonal chromosomal abnormalities involving 2p22-24, and fusion of the ALK gene with tropomyosin 3 (TPM3-ALK) or tropomyosin 4 (TPM4-ALK) is found in a subset.

Electron microscopy in the study of myofibroblastic lesions

Electron microscopy in the diagnosis and academic study of myofibroblastic lesions is discussed. Myofibroblasts from granulation tissue and tumor stroma are regarded as the nearest equivalent to a "normal" myofibroblast population with which to define myofibroblastic differentiation in tumoral and pseudotumoral lesions. Histological features include a plump-spindle-cell morphology, with an ill-defined cytoplasm paler and less fibrillar than in smooth-muscle cells, and matrix collagen. Myofibroblasts stain for alpha-smooth-muscle actin, fibronectin, and vimentin. Desmin is found in some lesional myofibroblasts. The main ultrastructural features are prominent rough endoplasmic reticulum, modestly developed myofilaments with focal densities ("stress fibers"), and fibronexus junctions. The latter are foci on the cell surface where intracellular myofilaments and extracellular fibronectin filaments converge. Myofibroblastic lesions vary in the extent to which they mirror this overall phenotype. Hypertrophic scar, Dupuytren's disease, nodular fasciitis, the fibromatoses, and inflammatory myofibroblastic tumors have the most developed myofibroblastic features. Keloid, postoperative spindle-cell nodule, and fibroma of tendon sheath are less well differentiated. Myofibroblastoma is among many lesions described as myofibroblastic which, however, appear to show a kind of smooth-muscle differentiation. Some spindle-cell malignancies express myofibroblastic features.

Fine needle aspiration of breast myofibroblastoma. A case report

BACKGROUND

The use of fine needle aspiration cytology (FNAC) for the diagnosis of breast diseases in men has received little attention. We report the cytologic and histologic findings of myofibroblastoma of the breast in a 52-year-old man.

CASE

Smears disclosed irregular and cohesive sheets of cells, with ill-defined cytoplasm and oval nuclei containing single nucleoli. The nuclear membrane was frequently grooved, and occasional intranuclear cytoplasmic inclusions (pseudoinclusions) were also found. The background was clean and contained scarce collagenous stroma and fragments of myxoid material. To the best of our knowledge, there have been only seven previous reports of breast myofibroblastoma in which the cytologic features are well documented, and none of them mention the presence of pseudoinclusions.

CONCLUSION

FNAC could suggest the diagnosis of this distinctly uncommon tumor if evaluated together with the clinical and radiologic findings.

Intranodal myofibroblastoma: study of a case suggesting smooth-muscle differentiation

A case of intranodal myofibroblastoma with amianthoid fibres was studied by histology, immunohistochemistry and electron microscopy, in a Canadian Caucasian male presenting with an inguinal mass which appeared following a sports injury. Tumour cells were spindled and formed haphazard interlacing fascicles with intervening areas of haemorrhage. They were positive for vimentin, alpha-smooth-muscle actin and HHF35. By electron microscopy, they displayed moderate numbers of rough endoplasmic reticulum cisternae, fine actin-sized filaments in cell processes, and discrete stretches of unambiguous lamina ('external' lamina), sometimes in association with short attachment plaques. The fibronectin fibrils and fibronexus junctions characteristic of myofibroblasts were not seen. The absence of fibronexus junctions and the presence of surface features typical of smooth-muscle cells (attachment plaques with overlying lamina) suggest that this tumour is not myofibroblastic but is exhibiting a degree of smooth-muscle differentiation. The findings confirm earlier observations suggesting that some intranodal myofibroblastomas are not myofibroblastic, but show a form of smooth-muscle differentiation.

Myofibroblastic tumours: neoplasias with divergent behaviour. Ultrastructural and flow cytometric analysis

Myofibroblasts are spindle cells having ultrastructural features in common with smooth muscle cells and fibroblasts. In the last few years, tumours have been described in which myofibroblasts represent not only a reactive mechanism but also a true neoplastic component. They constitute new nosologic entities which might be termed "myofibroblastic tumours". Tumours with benign and, rarely, malignant behaviour are reported to belong to this group of lesions. Recently, a third tumour type with borderline biological course, named "inflammatory myofibroblastic tumour" (IMT), has been identified, a condition that has been regarded as a benign and reactive disorder for a long time. Only in recent reports has been demonstrated that, in spite of an apparently benign morphological pattern, some cases of IMT have a malignant course. In this connection, DNA analysis by flow cytometry is a valuable diagnostic tool, because it allows identification of the ploidy status, a procedure that is often useful for predicting the nature and the biological behaviour of the lesion. In this study, 11 cases of myofibroblastic tumours were examined retrospectively by evaluating clinicopathological features and DNA ploidy status by flow cytometry. The diagnosis of myofibroblastic tumour was confirmed by performing histology, immunohistochemistry, and electron microscopy in all patients. In detail, these 11 cases were composed of 1 benign myofibroblastoma, 1 myofibrosarcoma and 9 IMTs. Among these myofibroblastic tumours, all those with local recurrence or distant metastases (one myofibrosarcoma and three IMT) showed an aneuploid cell population demonstrable by flow cytometric analysis, whereas the other cases with benign course (one benign myofibroblastoma and six IMT) exhibited an euploid DNA content. These data suggest the following: a) Besides the rare myofibroblastomas and myofibrosarcomas, IMTs represent a larger group of lesions with potentially different biological and clinical course. b) DNA flow cytometric analysis is a reliable tool that support histopathological examination in characterizing those cases of IMT that, though being malignant, mimic benign lesions. Consequently, it establishes the basis for a different therapeutic approach according to the euploid or aneuploid DNA content.

Myofibroblastoma of the neck in a heifer

A 1.5-year-old Holstein heifer had a subcutaneous tumor mass (20 cm diameter) on the ventral portion of the neck, and the tumor was diagnosed as a locally invasive myofibroblastoma. It consisted of moderately cellular fibrous tissue, and the interlobular septum of the thymus was invaded by tumor cells. The neoplastic cells were positive for alpha smooth muscle actin and vimentin, but not for desmin. Electron microscopy disclosed the presence of moderately developed rough endoplasmic reticulum and microfilaments with focal densities.

Myofibroblastoma of the ovary: report of a case

We report an unusual case of an ovarian tumor arising in a 22-year-old female that showed histologic, immunohistochemical, and ultrastructural features of myofibroblastic differentiation. The mass was found incidentally and upon excision was 9.0 cm in its greatest dimension and almost entirely replaced the left ovary. The patient is alive without evidence of disease 21 months after excision. Histologically, the tumor was encapsulated and composed of cytologically bland spindled cells arranged into a variety of patterns, similar to those found in both solitary fibrous tumor and hemangiopericytoma. Immunohistochemically, the cells stained strongly for smooth muscle actin and muscle-specific actin, with only focal and weak staining for CD34. Stains for S-100 protein, desmin, and AE1/AE3 were negative. Ultrastructurally, the neoplastic cells showed clear-cut evidence of myofibroblastic differentiation. The differential diagnostic considerations, including solitary fibrous tumor and hemangiopericytoma, are discussed.

Myofibroblastoma of breast: evidence favoring smooth-muscle rather than myofibroblastic differentiation

A histopathological study of two cases of the tumor known in the literature as myofibroblastoma of the breast is presented. The tumors occurred in Caucasian males aged 57 and 62 years. Histologically, these were moderately cellular, lobulated spindle-cell lesions, each with a reasonably well-delineated edge with surrounding fatty connective tissue. No breast ducts or lobules were present. Tumor cell nuclei were bland, with small nucleoli and some nuclear grooving. Nuclear atypia and mitoses were absent. Immunostaining revealed positivity for a-smooth-muscle actin, desmin, and CD34. Tumor cells contained rough endoplasmic reticulum, bundles of myofilaments with focal densities, intermediate filaments, attachment plaques alternating with plasmalemmal caveolae, and focal lamina. Ultrastructural findings pointed to true smooth-muscle differentiation, and the cell-surface in particular lacked surface features of myofibroblasts (fibronectin fibrils [microtendons] and fibronexus junctions). These and published data suggest that at least some of the lesions referred to in the literature as myofibroblastoma may not be myofibroblastic and may be better designated as myogenic stromal tumors or as variants of leiomyoma.

Benign spindle cell tumor of the breast with prominent adipocytic component

We report a rare case of "benign spindle cell tumor of the breast with prominent adipocytic component" and present a review of the literature on the topic. The close morphologic resemblance with myofibroblastoma and spindle cell lipoma of the breast is emphasized and used as a starting point for diagnostic and histogenetic considerations. Although immunocytochemistry and electron microscopy showed features favoring a diagnosis of spindle cell lipoma, they were not conclusive. The tumor described here contributes to widen the spectrum of the benign spindle cell tumors of the breast variously named "benign spindle cell tumor," myofibroblastoma, spindle cell lipoma, and fibroma. It is important to distinguish this lesion from spindle cell metaplastic carcinoma and aggressive fibromatosis.

Myofibroblastoma of breast--an appraisal of cytoskeletal phenotypes

Myofibroblastoma of the breast is a recently described entity. Since its first description in 1987, less than 50 cases have been reported. We present the first (reported) myofibroblastoma to be detected as a non-palpable mass on a routine screening mammogram and emphasize the importance of not mis-diagnosing this rare cellular lesion as malignant on frozen section. Review of the literature demonstrates changes in the clinical presentation of myofibroblastomas. Once considered more common in men than in women, myofibroblastomas are now being reported with increasing frequency in women. The age at presentation is a decade earlier, and not surprizingly, the size of the earlier detected lesion is smaller. Recently four different cytoskeletal phenotypes (V, VA, VAD and VD) of myofibroblastomas have been described, depending upon the vimentin (V), actin (A), and desmin (D) immunoreactivity. Whereas vimentin reactivity is universal, actin and desmin immunoreactivity is variable, desmin being more frequently positive than actin. As more is known about the clinical behavior of myofibroblastomas, their rate of recurrence and malignant potential, if any, the relationship of the cytoskeletal content to prognosis may become clearer. Currently, complete immunohistochemical analysis and electron microscopic examination of this interesting breast lesion is recommended. List of abbreviations-Vimentin (V), actin (A), and desmin (D), vimentin and actin (VA), vimentin and desmin (VD), vimentin, actin and desmin (VAD).

Intranodal palisaded myofibroblastoma with so-called amianthoid fibers: a report of two cases with a review of the literature

Two cases of intranodal myofibroblastoma, a rare primary spindle cell tumor of the lymph node, are described. The tumors arose in the inguinal or proximal region of the thigh of one middle-aged and one elderly Japanese male. The tumors were well-demarcated and composed of a fascicular proliferation of spindle cells with focal nuclear palisading and acellular stellate-shaped collagen-rich areas (so-called amianthoid fibers), and were associated with hemorrhagic areas. Immunohistochemically, the tumor cells were positive for vimentin and muscle actin. Together with ultrastructural findings of intracytoplasmic microfilaments with focal densities and profiles of well-developed, rough endoplasmic reticulum, these features reinforced the conclusion of myofibroblastic or smooth muscle differentiation of the tumor cells. One of the tumors was analyzed by flow cytometry and was shown to be DNA diploid. The present report provides clinicopathological findings of the first two Japanese cases of intranodal myofibroblastoma.

Angiomyofibroblastoma of the vulva: a mitotically active variant?

A case of angiomyofibroblastoma in a 48-year-old woman is reported. The tumor occurred as a left vulval mass and was treated by simple excision. It was located in the subcutaneous tissue of the left vulva and was well circumscribed, measuring 2.8 x 2.7 x 2.5 cm. Microscopically, the tumor was composed of hypocellular and cellular areas with well-developed small vessels. Spindle or polygonal cells were arranged with perivascular accentuation in an edematous or fibrocollagenous background. Some spindle-shaped or polygonal stromal cells were also arranged in epithelioid nests. In some areas, mitoses were frequent (maximum 3/10 high-power field). Immunohistochemically, the stromal cells were positive for vimentin and desmin, but negative for alpha-smooth muscle actin, S-100, neurofilament, estrogen receptor, progesterone receptor, CD31 and CD34. The average labeling index of Ki-67 in stromal cells was 3.1%. Ultrastructural analysis demonstrated that the stromal cells adhered with primitive junctions and contained intermediate filaments with no focal density in the cytoplasm. These findings were consistent with angiomyofibroblastoma, although previously reported cases did not show so many mitoses. Therefore, this case was suggested to be a mitotically active variant.

Angiomyofibroblastoma of the vulva with sarcomatous transformation ("angiomyofibrosarcoma")

We report on a locally recurrent vulvar tumor in an 80-year-old woman that we believe represents the first example of malignant transformation of an angiomyofibroblastoma. The tumor was predominantly a typical angiomyofibroblastoma, composed of epithelioid or oval cells with eosinophilic cytoplasm that tended to cluster in small groups and around blood vessels. These areas merged imperceptibly with a high-grade sarcoma that resembled a myxoid malignant fibrous histiocytoma. The tumor cells in the benign areas were diffusely immunoreactive for vimentin; many cells were positive for smooth muscle actin, and focal positivity for muscle actin and desmin was observed. The tumor cells in the sarcomatous areas were diffusely positive for vimentin, but negative for smooth muscle actin, muscle actin, and desmin. No staining for keratin, S-100 protein, or CD34 was noted. Ultrastructural examination of the sarcomatous area showed that the cells had the features of fibroblasts. All previously reported cases of angiomyofibroblastoma have exhibited banal histologic features and have behaved in a benign fashion. This case shows that these tumors may rarely be associated with a malignant component, and the designation "angiomyofibrosarcoma" may be appropriate in such cases.

[Immunohistochemical and ultrastructural study of a case of carcinosarcoma (biphasic sarcomatoid carcinoma) of the lung with rhabdomyoblastic differentiation]

Histologic, immunohistochemical and ultrastructural features of a case of carcinosarcoma of the lung are described. The biphasic pattern of this neoplasm is characterized by the presence of a carcinomatous component that corresponds to an adenosquamous carcinoma, and a sarcomatous component with rhabdomyoblastic differentiation. Since the biphasic sarcomatoid carcinoma has an aggressive clinical behaviour, immunohistochemical expression of prognostic markers, such as Ki-67 and p53 is evaluated to individuate differences between the carcinomatous and the sarcomatous components of the tumor. The higher p53 expression and Ki-67 positivity in the former, suggests that the carcinomatous component probably represents the more aggressive portion of the tumor. Moreover, P53 expression is nuclear in both carcinomatous and sarcomatous areas, thus it is likely that the biphasic sarcomatoid carcinoma of the lung is monoclonal in origin.

Myofibrosarcoma of the breast: review of the literature on myofibroblastic tumors and criteria for defining myofibroblastic differentiation

A case of myofibrosarcoma of the breast is described. A 55-year-old woman presented with a small mammary nodule. A large recurrent lesions appeared a month later, and the patient died 11 months following initial presentation from diffuse pleuropulmonary metastases. Histologically, the primary tumor consisted mainly of spindled cells, arranged in fascicles and surrounded by varying quantities of dense hyaline collagen. The recurrent lesion had a more pleomorphic organization. In both lesions, there was positive immunostaining for vimentin, smooth-muscle actin, and fibronectin, and negative results for desmin, laminin, and type IV collagen. Electron microscopy revealed abundant rough endoplasmic reticulum, myofilaments with focal densities, and the fibronexus junctions and fibronectin fibrils characteristic of myofibroblasts. Given these cellular features and behavior, the tumor was interpreted as a malignant neoplasm showing myofibroblastic differentiation, i.e., a myofibrosarcoma. This case enlarges the group of myofibrosarcoma of breast, also with the demonstration of fibronexus and fibronectin fibrils. The paper emphasizes the criteria required for myofibroblastic differentiation and reviews lesions of the breast reported in the literature as myofibroblastic.

The many faces of smooth muscle neoplasms in a gynecological sampling: an ultrastructural study

Smooth muscle neoplasms may have a variety of light microscopic and ultrastructural appearances. On one extreme, a spindle cell mass with a fascicular pattern, located in the myometrium, usually does not need electron microscopy or immunohistochemistry to confirm its smooth muscle nature. However, at the other end of a spectrum is an epithelioid neoplasm of the extrauterine pelvic tissues that could be composed of any of several cell types if routine light microscopy, alone, were used in studying it. In this report, some of these variants of smooth muscle neoplasms are exemplified, including myxomatous, fibroblast-like, nondescript, epithelioid, granular cell, and clear cell types. The main purpose has been to address, in particular, the ultrastructure of these unusual neoplasms, but, at the same time, not to ignore or downplay the contributory role of immunohistochemistry in making a final diagnosis, in some cases. Especially intriguing were the ultrastructural characteristics of leiomyomatous granular cell and clear cell neoplasms. A paucity or absence of filaments and dense bodies in samplings of these lesions makes the reliance on other ultrastructural features extremely useful.

[Myofibroblastoma of the lymph nodes]

We report a case of intranodal myofibroblastoma occurring in a lymph node of the left inguinal region of a 53 years old female. This tumor was first described 6 years ago and has not been yet documented in the Hungarian literature. This rare benign mesenchymal neoplasm of the lymph node occurs almost exclusively in the inguinal region. Histologically the tumor is characterized by interlacing fascicles of spindle cells which show nuclear palisading and the presence of hemorrhage. Immunohistochemically, the tumor cells were positive for actin and vimentin. Electronmicroscopic investigation demonstrated features characteristic for myofibroblastic origin. Characteristic amianthoid structures were occasionally present. It is important to distinguish this tumor entity of other primary or secondary mesenchymal neoplasms of lymph nodes including nodal involvement of Kaposi's sarcoma, a lesion it may closely resemble.

Subclassification of gastrointestinal stromal tumors based on evaluation by electron microscopy and immunohistochemistry

Fifty-six gastrointestinal stromal tumors (GIST) were subclassified by ultrastructural examination and by immunophenotypic analysis using a panel of 13 antibodies. Eighty percent of the tumors originated in the stomach and small intestines. The neoplasms were classified as follows: 42.9% smooth muscle tumors (4 leiomyomas, 9 spindle cell and 8 epithelioid leiomyosarcomas, and 3 mixed spindle cell and epithelioid leiomyosarcomas); 37.5% gastrointestinal autonomic nerve tumors (GANT), 47.6% of which arose in the small intestines; 8.9% mixed leiomyosarcoma/neurogenic tumors; and 10.7% undifferentiated GIST, not otherwise specified. The muscle common actin antibody HHF-35, variably reactive with tumor cells composing 23 of 24 smooth muscle tumors, was found to be the most sensitive marker of leiomyocyte differentiation. One immunophenotypically questionable spindle cell leiomyosarcoma was diagnosed by electron microscopy. Since neuron specific enolase positive cells were found in 1/3 of the leiomyosarcoma cases, the ultrastructural demonstration of synapse-like structures and neurosecretory granules was required for diagnosing GANTs. The immunophenotype of the ultrastructurally undifferentiated GIST was vimentin and CD34+. Variable numbers of ultrastructurally undifferentiated cells also we found in all of the tumors except 2 leiomyomas. CD34 was also expressed in smooth muscle (54%) and GAN (62%) tumors. Despite their similar light microscopic appearance, GIST are phenotypically heterogeneous, requiring both ultrastructural and immunohistochemical studies for accurate characterization.

Intranodal myofibroblastoma: report of a case

Palisaded myofibroblastoma (hemorrhagic spindle cell tumor) is a recent addition to the group of benign primary spindle cell lesions of lymph nodes. These tumors are characterized histologically by hemorrhage, palisading, and foci of collagen called amianthoid fibers. We report a further typical example with the aim of discussing its differentiation. Tumor cells were positive for smooth-muscle actin and vimentin. The cytoplasm contained moderate numbers of rough endoplasmic reticulum cisternae and some smooth-muscle type myofilaments. Subplasmalemmal densities and plasmalemmal caveolae, as well as material interpreted as external lamina, were identified at the cell surface, whereas the fibronexus junctions typical of myofibroblasts were not seen. Immunostaining for type IV collagen was positive. Intranodal myofibroblastomas have largely been considered as myofibroblastic, but the observations presented here raise the alternative possibility of simple smooth-muscle differentiation. The foci of collagen widely referred to as amianthoid fibers contained fibrils mostly of conventional diameter, 50-83 nm. The giant collagen fibrils typical of true amianthoid change were absent. It is suggested that the term amianthoid be used only after ultrastructural confirmation of the presence of giant collagen fibrils.

Ethmoidal myofibroblastoma

Myofibroblastoma is an uncommon mesenchymal tumour characterized by spindle cells exhibiting the ultrastructural and immunohistochemical features of myofibroblasts. We report a case of a myofibroblastoma occurring in the ethmoid sinus, which to our knowledge is the first case reported in the literature. The clinical presentation, diagnosis, histology, and management of this lesion is discussed with a review of the relevant literature.

Myofibroblastoma of the axilla

A mass in the axilla of a 47-year-old woman was biopsied and resected. The mass was composed of a loosely distributed population of spindle cells that were immunoreactive for smooth-muscle actin. Ultrastructurally, the cells possessed abundant endoplasmic reticulum, and some contained peripheral smooth muscle myofilaments, establishing that they were myofibroblasts. Mitotic activity was sparse, there was no cytologic atypia, and by flow cytometry the tumor was diploid with a low S phase. A diagnosis of myofibroblastoma was favored, although the possibility of a low-grade sarcoma could not be excluded. There has not been any indication of recurrence over a 4-month period of follow-up.

Gastro-intestinal stromal tumors: an ultrastructural reinterpretation of the clear cell component

The histology, immunohistochemistry and ultrastructure of six gastro-intestinal stromal tumors of the stomach (GSTs) showing a focal to diffuse clear cell component are reported. At light microscopy, all GSTs had typical histopathological features with one case additionally displaying stromal myxoid changes and scattered multinucleated giant cells. Immunohistochemically, 6 of 6 GSTs stained positive for vimentin, 2 of 6 for smooth muscle specific actin and 1 of 6 for desmin. At electron microscopy, GSTs showed microfilaments with focal densities as well as other smooth muscle features, such as subplasmalemmal linear densities and foci of external lamina. Ultrastructural appearances of tumor cells with clear cell features showed these not to be an artifact of fixation, but the expression of an unusual cytophagocytic activity. Inclusions of auto- and heterophagocytic nature were found responsible for the origin of the large, mostly lipidic vacuoles which displaced cell nuclei peripherally in a signet-ring fashion. It is concluded that such previously unrecognized features are ultrastructural aspects of GSTs with smooth muscle differentiation.

Establishment of three rat soft tissue tumor cell lines with different degrees of myogenic differentiation

Soft tissue malignancies often show divergent differentiation, including myogenic lineage. Five rat tumors induced with 20-hydroxymethylcholanthrene (20-OH-MCA), were cultured in vitro, and three cell lines (YMC-1, YMC-2, YMC-3) were established from them. YMC-2 and -3 cells were spindle-shaped, and YMS-1 cells round and epithelioid. In confluency, YMC-3 cells formed myotubes. The nude mouse xenotransplants showed morphological features consistent with their myogenic phenotypes. Muscle-specific enzyme activities were highest in YMC-3 cells. These lines may be useful in the investigation of the myogenic differentiation of undifferentiated mesenchymal cells.

Fine-needle aspiration cytologic study of myofibroblastoma of the breast. Immunohistochemical and ultrastructural findings

Myofibroblastoma of the breast is a recently recognized benign stromal tumor arising from the breast mesenchyma. Myofibroblastomas are grossly circumscribed, unencapsulated tumors that are most commonly found in males. Histologically, myofibroblastomas comprise predominantly bipolar spindle cells arranged either haphazardly or in fascicles that traverse a collagenous background. Their ultrastructural and immunohistochemical profiles are consistent with myofibroblastic differentiation. Myofibroblastoma of the breast was discovered in a 64-year-old man. For the first time the fine-needle aspiration findings are reported, as are the histologic, immunohistochemical, and ultrastructural findings.

Palisaded intranodal myofibroblastoma. Electron microscopic study

Described in this paper are the ultrastructural features of three cases of palisaded intranodal myofibroblastoma. The tumor cells were identified as myofibroblasts. Abortive vessels formed by the tumor in one case and spindle cell tumorous proliferation outside the tumor capsule and centered on the veins were composed of the same cell types as the cells of the main tumor mass, suggesting that the tumorous myofibroblasts might have originated from the modified smooth muscle cells. The various stages of formation of the intracytoplasmic fuchsinophilic bodies are described in our report.

Endometrial stromal nodule with smooth and skeletal muscle components simulating stromal sarcoma

A stromal nodule was found in a hysterectomy specimen from a 29-year-old woman with a history of menometrorrhagia. Endometrial curettings had revealed stromal cells admixed with well-defined bundles of smooth muscle cells, a finding that had led to the erroneous diagnosis of stromal sarcoma invading the myometrium. Ultrastructural and immunohistochemical studies demonstrated several components: stromal cells, smooth muscle cells, sex-cord-like structures, and a hitherto undescribed component of skeletal muscle cells.

Nucleolar organizer regions in smooth muscle and breast tumours

Paraffin sections of formalin fixed tissues, obtained from patients with smooth muscle and breast tumours, were studied by the silver staining technique to quantitate the Nucleolar Organizer Regions (AgNORs) per nucleus and to assess its significance as an independent variable in predicting the behaviour of these neoplasms. Five benign and five malignant tumours of smooth muscle along with ten benign and ten malignant epithelial tumours of breast were studied. Normal myometrium and breast tissue served as controls. Control, benign and malignant tumours of smooth muscle showed mean AgNOR scores of 2.68, 3.89 and 12.50 per nucleus respectively. Control, benign and malignant tumours of breast showed mean AgNOR scores of 1.75, 7.45 and 12.72 per nucleus respectively. These results suggest that quantitative analysis of AgNORs per nucleus is capable of differentiating benign from malignant lesions of smooth muscle and breast.

Intranodal "amianthoid" myofibroblastoma. Report of six cases immunohistochemical and electron microscopical study

Six cases of intranodal amianthoid myofibroblastomas are reported. Immunohistochemically the tumors were actin positive and S-100 protein and desmin negative. Intracytoplasmatic, actin-rich bodies, previously found to be a characteristic feature of this tumor, were identified as cytoplasmatic extensions filled with microfilaments at an ultrastructural level. Abortive vessel formation by the tumor cells and the proliferation of tumor cells centered on veins outside the capsule of the tumor in two of our cases indicated a close relationship between the intranodal palisaded myofibroblastoma and the musculature of vascular origin.

Immunohistochemical identification of aggregated actin filaments in formalin-fixed, paraffin-embedded sections. I. A study of infantile digital fibromatosis by a new pretreatment

Some authors have claimed that actin is not immunostained in characteristic intracytoplasmic inclusions of infantile digital fibromatosis, whereas others have claimed that it is. Formalin-fixed specimens were used in the former studies; specimens fixed in alcohol used in the latter studies. Actin at other sites, such as the rim of the inclusions, was distinctly immunostained even in the formalin-fixed specimens. Such phenomena make it difficult to accept the loss of antigenicity of actin as a result of formalin fixation. The use of usual pretreatment with trypsin provided the same results. We were able to immunostain actin distinctly and strongly in the inclusions for the first time in formalin-fixed specimens by combining KOH in 70% ethanol and trypsin. This successful staining results from the adequate etching effect of trypsin, which occurs because of a loosening of proteins in the inclusions due to KOH. These phenomena suggest that steric hindrance of antigen determinant has occurred only in the inclusions as a result of intramolecular cross-linkage, because of extremely dense accumulation of actin filaments in the inclusions.

Intranodal myofibroblastoma in a submandibular lymph node. A case report

A typical case of intranodal myofibroblastoma arising in a submandibular lymph node is reported. It provides proof that this tumor can occur in extrainguinal regions and suggests that the submandibular region is a prevalent site. The combination of benign spindle cells and foci of pale fibrillary matrix and hemosiderin granules were characteristic features in the fine-needle aspiration cytologic findings.

Soft tissue myofibroblastomas

Five well-circumscribed solitary soft tissue tumors composed of myofibroblasts are described and termed myofibroblastomas. By light microscopy these lesions are characterized by short, intersecting, or crisscrossing fascicles of spindle cells, sometimes associated with foci of necrosis and/or mitotic activity with less than three mitoses per 10 high power fields. Myofibroblastomas show well-defined myofibroblastic differentiation ultrastructurally with peripheral myofilaments and vimentin, actin, and desmin immunocytochemistry positivity. The five tumors described occurred in patients of various age groups, including one congenital, and in a variety of soft tissue locations. It is important to recognize this benign soft tissue neoplasm to avoid confusion with other soft tissue tumors and to separate this lesion from other myofibromatosis. This study elucidates the spectrum of light microscopic, ultrastructural, and immunocytochemistry findings of soft tissue myofibroblastomas and establishes this soft tissue tumor as a specific clinico-pathologic entity.

Central granular cell tumor of the jaw. An electron microscopic and immunohistochemical study

Central granular cell tumor of the jaw was formerly known as granular cell ameloblastic fibroma; recently, the term central granular cell odontogenic fibroma has been proposed. This study attempts to determine the ultrastructural features and selected immunohistochemical properties of the tumor cells. Four formalin-fixed specimens were processed for electron microscopy, and for immunohistochemical staining with antiactin, anti-glial fibrillary acidic protein, and OKT6 (CD1) with the avidin-biotin-peroxidase complex method. Tumor cells contained many primary lysosomes, autophagic vacuoles, and phagocytic vacuoles. The phagocytic vacuoles appeared to contain collagen fibrils. Tumor cells stained positive with antiactin and OKT6 (CD1), and negative with anti-glial fibrillary acidic protein. The results indicate that tumor cells are actively phagocytic and suggest that tumor cells might arise from Langerhans' cells.

Malignant granular cell tumor

A malignant granular cell tumor (MGCT) appeared on the subungual tissue of the right index finger of a 51-year-old woman. Two years after resection of the tumor, it recurred, and the finger finally had to be amputated. Six months later, she noticed multiple cutaneous nodules on her trunk. Despite chemotherapy and X-ray irradiation, the patient died 18 months after the second operation. Histology of the specimen revealed a proliferation of both polygonal and spindle-shaped cells with large hyperchromatic nuclei and an eosinophilic granular cytoplasm. Peripheral nerves were encompassed by the tumor cells. Immunohistochemically, the tumor cells were positive for S-100 protein and Leu 7 (myelin-associated glycoprotein). These findings support the hypothesis that MGCT cells are of Schwann cell origin.

Granular cell tumours of the orbit

Granular cell tumours are uncommon benign tumours, occurring in various sites in the body, and very rarely in the orbit or ocular adnexa. Four cases of orbital granular cell tumour are described, with detailed light and electron microscopic description of one tumour arising in the orbital apex of a child. The histogenesis of granular cell tumour is uncertain, with many authors proposing an origin from Schwann cells. In central nervous system granular cell tumours, an astrocytic cell origin has been proposed. Evidence is presented for an origin from astrocytes in a child whose tumour arose in or adjacent to the optic nerve.

Granular cell tumors of the vulva

Granular cell tumor (GCT), although nearly ubiquitous, is seen infrequently in the vulva. A review of the surgical pathology files from Grady Memorial Hospital, Atlanta, Georgia, from 1983 through 1987 identified eight cases of vulvar GCT. Five of the eight patients had more than one skin and soft tissue lesion. Two of the five had biopsy-proven multicentric GCT with a unique clinical course. One of the patients was a 32-year-old woman with multiple vulvar, lingual, laryngeal, bronchial and pulmonary GCT, necessitating multiple excisions and ultimately pneumonectomy. The second patient had multiple GCTs in the vulva and inguinal area and finally in both lungs, resulting in her death at age 39. No dependable microscopic features could be identified to distinguish benign GCT from its more aggressive variant. However, Feulgen DNA histomorphometry demonstrated aneuploidy in the patient with apparent lung metastases, whereas the tumors from patients with a benign course as well as from the patient with multiorgan involvement were diploid. In three of five patients who could be interviewed there was a history of soft tissue tumors in members of the family. The multifocal nature and possible familial component of GCT need to be explored further.

Comparison of a human granular cell tumour (myoblastoma) with granular cell tumours (meningiomas) of the rat meninges--an immunohistological and ultrastructural study

A single human granular cell tumour (myoblastoma) was compared with seven rat granular cell tumours (meningiomas) of the meninges. The comparison was made histologically, ultrastructurally and using immunocytochemical markers. A selection of antibodies to histiocytic, muscle, neural, neural crest and mesenchymal antigens was used. Histogenesis of both the human and rat tumours from neural crest-derived cells was evident and it is suggested that the term 'meningioma' for these rat tumours is a misnomer.

Mitochondria as a feature of smooth muscle differentiation: a study of 70 smooth muscle tumors

We report that the presence of numerous mitochondria is an ultrastructural feature of smooth muscle neoplasms which is diagnostically useful as a marker for smooth muscle differentiation. The number of mitochondria, as well as the usual features of smooth muscle differentiation, were studied in 70 smooth muscle neoplasms from a variety of body sites. The tumors were sub-classified according to the number of mitochondria (in the majority of the tumor cells) as sparse, moderate, abundant or packed. Thirty-one percent of the leiomyomas had sparse mitochondria and 69% had a moderate number of mitochondria. Seven percent of the leiomyoblastomas contained a moderate number of mitochondria, 33% contained abundant mitochondria and 60% were packed with mitochondria. Twelve percent of the leiomyosarcomas showed sparse mitochondria, 67% showed a moderate number of mitochondria, and 21% had abundant mitochondria. For the above tumor types, the cells with abundant and packed mitochondria contained few or no visible filaments, and these cells were often round or polygonal. By contrast, adjacent spindle cells often contained numerous filaments including dense bodies. The recognition of mitochondria as a feature of smooth muscle differentiation is diagnostically useful in tumor samples showing numerous mitochondria and a paucity of filaments and dense bodies.