Epithelioid glomus tumor

Incidental superficial soft tissue epithelioid angioleiomyoma

Epithelioid angioleiomyoma is rare in the skin and subcutaneous tissues. To our knowledge, only two previous cases of this tumor have been reported. We document here the case of an 83-year-old woman who underwent complete removal of a squamous cell carcinoma of the retromolar trigone and lymph node dissection of the neck. An incidental epithelioid angioleiomyoma was observed in the adipose tissue. The tumor formed a unilocular, poorly-demarcated neoplasm measuring 0.3 cm., and showed cavernous angiomatous spaces with villiform growth of large epithelioid cells arranged in clusters. Besides the epithelioid cells of muscular origin, bundles of well-differentiated smooth muscle cells were observed. Epithelioid cells accounted for 70% of the total. The neoplasm originated in the wall of a medium-sized vein. Epithelioid and spindle cells were positive for alpha-smooth muscle actin, calponin, h-caldesmon, and muscle-specific actin. The endothelial cells lining the vascular spaces showed intense and diffuse positivity for CD31 and ERG. The main differential diagnosis includes metastatic carcinoma, melanoma, perivascular epithelioid cell neoplasm (PEComa), myopericytoma, glomangiomyoma, epithelioid glomus tumor, and epithelioid leiomyosarcoma. This report expands the morphological spectrum of the epithelioid angioleiomyoma. Awareness of this uncommon morphologic variant of angioleiomyoma and the use of adequate techniques can avoid misdiagnosis. This article is protected by copyright. All rights reserved.

A Rare Case of Glomus Tumor on the Mucosal Surface of Lower Lip

Glomus tumors are mesenchymal neoplasms derived from glomus bodies with rare presentations in the oral cavity. Glomus tumors present as a purple or pink vascular nodule or papule, sized <1 cm, and imitate vascular neoplasms such as hemangiopericytoma or hemangioma. Glomus tumors represent less than 2% of all benign soft tissue tumors. Only 27 cases of benign glomus tumors with oral cavity involvement have been reported to date. The most-reported oral tumors involved the lips (54.2%), followed by hard palate, gingiva, tongue, and buccal mucosa. The mean age of presentation of the labial glomus tumors is 48.7 years, with no gender predilection, in contrast to the subungual site, which occurs more in females. The etiology of the glomus tumors remains unknown. Subungual glomus tumors present as stabbing pain, cold intolerance, and tenderness of the fingertips, whereas labial glomus tumors mostly present as a painless, small, and slow-growing lesion. Treatment is surgical resection of the tumor. The recurrence rate of labial glomus tumors is unclear. In this article, we present the case of a 62-year-old man with a 2-month history of painless, soft lump on the mucosal surface of the lower left lip. Excisional resection of the tumor was performed in the clinic, and the histopathologic finding was consistent with solid glomus tumor. At 1 year follow-up there was no recurrence.

Mesenchymal tumours of the gastrointestinal tract

Mesenchymal tumours represent a heterogenous group of neoplasms encopassing benign, intermediate malignancy, and malignant entities. Sarcomas account for approximately 1% of human malignancies. In consideration of their rarity as well as of intrinsic complexity, diagnostic accuracy represents a major challenge. Traditionally, mesenchymal tumours are regarded as lesions the occurrence of which is mostly limited to somatic soft tissues. However, the occurrence of soft tissue tumours at visceral sites represent a well recognized event, and the GI-tract ranks among the most frequently involved visceral location. There exist entities such as gastrointestinal stromal tumours (GIST) and malignant gastointestinal neuroectodermal tumors that exhibit exquisite tropism for the GI-tract. This review will focus also on other relevant clinico-pathologic entities in which occurrence at visceral location is not at all negligible.

Epithelioid Cutaneous Mesenchymal Neoplasms: A Practical Diagnostic Approach

Epithelioid cells are rounded or polygonal cells with abundant eosinophilic or clear cytoplasm and ovoid to round nuclei, superficially resembling epithelial cells. Cutaneous mesenchymal neoplasms composed predominantly or exclusively of epithelioid cells are relatively uncommon and can cause considerable diagnostic difficulties due to overlapping histologic features among heterogeneous groups of tumors. Familiarity with practical diagnostic approaches and recognition of key histopathologic features are important for correct diagnosis and management. This review summarizes the histologic features of epithelioid cutaneous mesenchymal neoplasms and discusses their differential diagnoses from malignant melanomas and carcinomas.

Glomus tumor in the floor of the mouth: a case report and review of the literature

Background

Glomus tumors are rare benign neoplasms that usually occur in the upper and lower extremities. Oral cavity involvement is exceptionally rare, with only a few cases reported to date.

Case presentation

A 24-year-old woman with complaints of swelling in the left floor of her mouth for 6 months was referred to our institution. Her swallowing function was slightly affected; however, she did not have pain or tongue paralysis. Enhanced computed tomography revealed a 2.8 × 1.8 × 2.1 cm-sized well-defined, solid, heterogeneous nodule above the mylohyoid muscle. The mandible appeared to be uninvolved. The patient underwent surgery via an intraoral approach; histopathological examination revealed a glomus tumor. The patient has had no evidence of recurrence over 4 years of follow-up.

Conclusions

Glomus tumors should be considered when patients present with painless nodules in the floor of the mouth.

Nail Unit Glomus Tumor with Myxoid and Symplastic Change Presenting with Longitudinal Erythronychia

Glomus tumors are soft tissue neoplasms, which are most frequently encountered in the nail unit and generally straightforward to diagnose by histopathology. The typical clinical presentation is that of a circular violaceous or erythematous lesion within the nail bed. However, there are rare variants of glomus tumors which may pose diagnostic challenges because of the presence of unusual histologic features. Herein we report such a glomus tumor that demonstrates the rare combination of both myxoid and symplastic change. The clinical presentation of longitudinal erythronychia, as seen with this case, can occur with glomus tumors, but it is unusual, as longitudinal erythronychia on a single nail usually is caused by an onychopapilloma. The distinct nuclear atypia characteristic of symplastic change can raise alarm for a malignant process but the clinical course is benign. It is essential for dermatopathologists to be aware of this unusual variant of a glomus tumor in order to avoid overdiagnosis of atypia, which could result in unnecessary aggressive surgery. While unusual, there is good clinicopathologic correlation of the glomus tumor presenting with longitudinal erythronychia.

Epithelioid Glomus Tumor of the Uterine Cervix: A Case Report and Review

Herein, we report a case of epithelioid glomus tumor involving the uterine cervix. A 67-yr-old woman with a long-standing history of cervical dysplasia underwent cervical conization. In addition to the patient's high-grade squamous intraepithelial lesion, histologic examination demonstrated an incidental, 0.2-cm glomus tumor in the cervical submucosa. The tumor was composed of bland epithelioid cells in scattered nests closely associated with small-caliber blood vessels. Immunohistochemically, the tumor cells were diffusely positive for smooth muscle actin and caldesmon and only focally positive for desmin and CD34. To our knowledge, only 2 similar case reports exist in the literature. The present case is the first cervical case seen with epithelioid features and in association with cervical dysplasia.

Unusual Glomus Tumor of the Penis

INTRODUCTION

Glomus tumors are benign neoplasms commonly found in subungual regions of the extremities and rarely located in the penis. Misdiagnosis of glomus tumors is common; therefore, symptoms and clinical presentations should be reviewed.

OBJECTIVE

The primary objective of this review article is to emphasize the pathogenesis, pathology, clinical presentation, symptoms, diagnosis, and treatment methods of glomus tumors in order to better identify and manage the condition.

MATERIALS AND METHODS

Research was conducted using PubMed/Medline. The inclusion criteria required glomus tumor to be present on the penis.

RESULTS

Glomus tumors, which appear as symptomatic or asymptomatic lesions, are attributed to dispersion grouping of neoplastic or non-neoplastic lesions in a particular area.

CONCLUSION

Differential diagnosis of glomus tumors includes hemangiomas, neurofibromatosis, epithelial lesions, and spindle-cell lesions. Physical examination and histological findings should be used for diagnosis. Treatment options can be either conservative or invasive, in which the patient undergoes surgical excision.

Glomangioma da artéria digital do polegar: relato de um caso

Os autores relatam um caso de tumor glômico em ramo da artéria radial que irriga o polegar direito, com história clínica de 4 meses. O doente referia o aparecimento de tumoração de aproximadamente 2,0 centímetros na região interdigital, entre o primeiro e o segundo quirodactilos da mão direita, sobre o músculo flexor curto do polegar, extremamente dolorosa e com dor em progressão. Os exames com aparelho de Doppler bidirecional e o eco-color-Doppler apresentaram, como diagnóstico presuntivo, malformação arteriovenosa, pelo turbilhonamento do fluxo e ausência de estenoses. A tumoração foi retirada por cirurgia aberta e encaminhada para exame histopatológico, com diagnóstico de glomangioma. Este relato descreve uma doença arterial pouco frequente, que causa extremo desconforto ao seu portador, mas que é solucionada pela exerese cirúrgica, sem sequelas.

Vascular and perivascular lesions of skin and soft tissues in children and adolescents

Vascular anomalies in children and adolescents are the most common soft tissue lesions and include reactive, malformative, and neoplastic tumefactions, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic complexity and recent changes in classification systems, some of which are based on clinical features and others on pathologic findings. In recent decades, there have been significant advances in clinical diagnosis, development of new therapies, and a better understanding of the genetic aspects of vascular biology and syndromes that include unusual vascular proliferations. Most vascular lesions in children and adolescents are benign, although the intermediate locally aggressive and intermediate rarely metastasizing neoplasms are important to distinguish from benign and malignant mimics. Morphologic recognition of a vasoproliferative lesion is straightforward in most instances, and conventional morphology remains the cornerstone for a specific diagnosis. However, pathologic examination is enhanced by adjunctive techniques, especially immunohistochemistry to characterize the type of vessels involved. Multifocality may cause some uncertainty regarding the assignment of "benign" or "malignant." However, increased interest in vascular anomalies, clinical expertise, and imaging technology have contributed greatly to our understanding of these disorders to the extent that in most vascular malformations and in many tumors, a diagnosis is made clinically and biopsy is not required for diagnosis. The importance of close collaboration between the clinical team and the pathologist cannot be overemphasized. For some lesions, a diagnosis is not possible from evaluation of histopathology alone, and in a subset of these, a specific diagnosis may not be possible even after all assembled data have been reviewed. In such instances, a consensus diagnosis in conjunction with clinical colleagues guides therapy. The purpose of this review is to delineate the clinicopathologic features of vascular lesions in children and adolescents with an emphasis on their unique aspects, use of diagnostic adjuncts, and differential diagnosis.

Symplastic glomus tumor: report of a challenging lesion with literature review

Glomus tumors are uncommon mesenchymal tumors whose cells closely resemble those of a normal glomus body, and are found most commonly in the hand. Recently, a symplastic form exhibiting marked nuclear atypia, in the absence of any other malignant features, has been described. To date, only 14 cases of symplastic glomus tumor have been reported in the literature; hence, very little information is available about its diagnosis, treatment, and biological behavior. The case reported here concerns a symplastic glomus tumor occurring in the right index finger of a 62-year-old woman. We reviewed the literature concerning previously reported cases, placing emphasis on the documented biological behavior, treatment, and demographic trend. Physicians must be aware of this morphological variation of glomus tumor to avoid the mistake of malignancy, which results in over-treatment of the patient.

Immunophenotypic analysis of glomus coccygeum associated with coccygodynia

OBJECTIVE

Glomus coccygeum is a glomus body which is found in the pericoccygeal soft tissue. This specialised arteriovenous anastomosis is a non-pathological vestigial structure usually larger than its equivalent in the distal extremities. Its prevalence is uncertain. Glomus coccygeum has been associated with coccygodynia and can cause diagnostic problems to pathologists unfamiliar with this entity.

MATERIALS AND METHODS

The presence of a glomus coccygeum was sought in 40 coccygectomy specimens and correlated with clinical, radiological and histological findings.

RESULTS

A glomus coccygeum was identified in 13 samples (35%). Glomus cells expressed smooth muscle actin (SMA) and were negative for desmin, S100, cytokeratin and a wide range of vascular markers. Proliferative activity was low. Pre-operative MRI did not identify these tiny lesions, and most patients with coccygodynia did not have a glomus coccygeum.

CONCLUSION

Glomus coccygeum is a common microanatomical structure which can be distinguished from glomus and other tumours by its small size, SMA expression and low proliferative activity.

Malignant glomus tumour: a case report and review of the literature

Purpose: Glomus tumours are characteristically benign solitary tumours. At our knowledge, about 23 reports are present in literature regarding the malignant counterpart, but only a minority developed metastases. We describe a locally aggressive glomus tumour with lymphnode metastasis.

Patient: The patient was a 40 year-old man presenting a 1.5-cm lesion on the right wrist incompletely excised and a recurrent tumour, 4 × 2 cm in size, removed after 9 months, for which he received radiotherapy. After 2 years he developed an axillary lymphnode metastasis.

Results: Histologically, both tumours (primary and metastasis) were similar. There were sheets and nests of uniform small cells with scant eosinophilic cytoplasm and round to polygonal nuclei; there was some degree of pleomorphism and the mitotic index was high (up to 18 m/10 HPF). The tumour cells were positive for vimentin and smooth muscle actin, but negative for desmin, NSE, Factor VIII, chromogranin, cytokeratin. Remarkably, in the primary, the cells strongly expressed p53 (70%) and MIB-1 (35%).

Discussions: In many reported malignant cases, the histology of the tumour cells suggested that they were malignant, yet the clinical course has been benign. Carefully reviewing the literature, it seems that actually we have enough histological criteria to identify the cases with biological adverse outcome. Those unfortunate cases behave as high grade sarcomas and therefore may deserve an aggressive therapeutic treatment.

Symplastic glomus tumor - a rare but distinct benign histological variant with analogy to other 'ancient' benign skin neoplasms

A 78-year-old woman presented with a nail deformity of the index finger of the left hand associated with paroxysmal pain upon cold exposure. Histologically, a well-circumscribed tumor of 3 mm diameter was found in the dermis. The neoplastic cells in some areas were of pronouncedly variable size and cytomorphology, mostly epithelioid in shape, with eosinophilic cytoplasm and indistinctly defined cell borders. Pronounced nuclear pleomorphism and atypia were striking features, but no mitotic figures were noted. Multinuclear cells were present as were numerous small-to-medium vessels throughout the tumor. The tumor stroma showed myxoid areas. Immunohistochemistry showed cytoplasmic and membranous expression of smooth muscle actin and vimentin. The histological features and immunoprofile were consistent with the diagnosis of symplastic glomus tumor, a rare histological variant, which has been defined as a glomus tumor exhibiting marked nuclear atypia, in the absence of any other criteria for malignancy. The biological behavior of the tumor is benign. It is essential to differentiate this entity from malignant glomus tumor, which has metastatic potential. Even prominent cellular atypia and nuclear pleomorphism in a glomus tumor as in our case is not a marker of malignancy in the absence of additional criteria.

Glomus tumor of the kidney: a report of 3 cases involving renal parenchyma and review of the literature

Glomus tumor is a rare mesenchymal neoplasm affecting the subcutaneous tissue of the distal extremities in the majority of cases. It only rarely involves visceral organs. We report 3 cases of the glomus tumor family in the kidney, a solid glomus tumor, a glomangioma, and a glomangiomyoma. All 3 tumors involved the renal parenchyma and occurred in 3 men aged 36, 81, and 48 years, respectively. All 3 tumors were well-circumscribed and showed morphology otherwise identical to those seen in soft tissue. All 3 tumors were immunoreactive for actin and negative for desmin and S100 and only 1 tumor expressed CD34 in tumor cells. To date, all 3 tumors have followed a benign course without evidence of recurrence or metastasis. This report expands the spectrum of mesenchymal tumors of the kidney.

Cutaneous Epithelioid Angioleiomyoma With Clear-Cell Change

Epithelioid angioleiomyoma is rare in the skin and subcutis. We report here an unusual case of epithelioid angioleiomyoma with prominent clear-cell change. Smooth-muscle differentiation was confirmed by immunostains. The extensive clear-cell change in epithelial cells and the marked hyalinization and calcification made the histologic differential diagnosis challenging. Epithelioid angioleiomyoma shares some histologic characteristics with glomus tumors and seems to be an intermediate entity between angioleiomyomas and glomus tumors.

Malignant Glomus Tumor

Malignant glomus tumor (MGT) is a rare, recently described neoplasm that recapitulates the appearance of the modified smooth cells of the normal glomus body. We report a case of MGT of the hand of a 48-year-old woman. Magnetic resonance imaging (MRI) showed a 2.8-cm, well circumscribed, enhancing mass on the volar aspect of the thenar region of the right hand in immediate continuity with the ulnar artery and nerve. Computed tomography scan (CT-Scan) of the chest was normal. Histologic evaluation revealed a multilobular lesion with prominent branching capillary vasculature and perivascular arrangement of sheets of tumor cells. The tumor cells were round, relatively uniform in size with distinct cell borders and perinuclear cytoplasmic clearing. They were of intermediate to high nuclear grade and showed significant mitotic activity. A wide local excision with negative margins was performed. Multiple lung metastases were evident at 8-month follow-up. To date, forty-five cases of MGT of skin and soft issue have been reported in the literature. Twelve of the forty-five cases developed metastasis. In this report, we emphasize the differential diagnosis of MGT in the skin and deep soft tissue.

Glomangiomyoma (Glomus Tumor) of the Kidney

We report herein a case of glomus tumor arising in the kidney of a 55-year-old woman, which was found incidentally on a computed tomographic scan. Partial nephrectomy revealed a 2-cm encapsulated mass that was architecturally similar to glomus tumor. Immunohistochemistry showed positivity of tumor cells for vimentin and smooth muscle actin. On electron microscopy, cytoplasmic thin filaments and dense bodies were seen, confirming the smooth muscle nature of the tumor. Glomus tumors arising in visceral organs are rare, and those arising in kidney are exceedingly rare.

Glomus tumour in the digit of a dog

The gross and microscopical features of a glomus tumour in the digit of a 9-year-old dog are described. The tumour consisted of a red nodule near the nail of the third digit of the right forelimb and appeared painful. The tumour cells, which had round to oval hyperchromatic nuclei and scant cytoplasm, were arranged in sheets around blood vessels, or in nests or duct-like structures. This pattern has not been described previously in canine glomus tumours. Mitotic figures were seen only occasionally. Tumour cells were strongly immunolabelled for vimentin and some expressed smooth-muscle actin and desmin. They were negative for cytokeratins, neuron-specific enolase and CD34. Silver impregnation (reticulin method) stained the reticulum around blood vessels, nests of tumour cells and duct-like structures, and a delicate reticulum was seen around each tumour cell. The morphological, immunohistochemical and histochemical patterns helped in the diagnosis of this glomus tumour.

Atypical and malignant glomus tumors: analysis of 52 cases, with a proposal for the reclassification of glomus tumors

Occasional glomus tumors display unusual features, such as large size, deep location, infiltrative growth, mitotic activity, nuclear pleomorphism, and necrosis. Although a small number of purportedly malignant glomus tumors have been described, histologic criteria for malignancy in glomus tumors have never been elaborated. The authors studied 52 unusual glomus tumors (retrieved from their consultation files) previously diagnosed as "atypical" or "malignant" by virtue of nuclear atypia, infiltrative growth, or mitotic activity. They evaluated size, depth, growth pattern, cellularity, nuclear grade, number of mitotic figures per 50 high-power fields (HPF), atypical mitotic figures, vascular space involvement, and necrosis to define criteria for malignancy in glomus tumors. Estimated relative risk was calculated and the Fisher exact test was used for statistical analysis. The 27 female patients and the 25 male patients ranged in age from 8 to 83 years (median age, 43 years). The tumors measured from 0.2 to 12 cm (median size, 2 cm) and occurred predominantly in the extremities, in both the superficial (n = 35) and deep (n = 17) soft tissues. Atypical features were usually observed centrally with a rim of benign-appearing glomus tumor. Follow-up information (n = 35; range, 5 months-23 years; mean 5.5 years) showed seven recurrences, eight metastases, and seven deaths from disease. Five-year cumulative metastatic risk increased significantly for tumors with a deep location (p = 0.005), with a size of more than 2 cm (p = 0.004), and with atypical mitotic figures (p = 0.004). Mitotic activity of more than 5 mitoses/50 HPF, high cellularity, the presence of necrosis, and moderate to high nuclear grade approached but did not reach significance. High nuclear grade alone, infiltrative growth, and vascular space involvement were not associated with metastasis. The authors propose the following classification scheme and criteria. Malignant glomus tumor: Tumors with a deep location and a size of more than 2 cm, or atypical mitotic figures, or moderate to high nuclear grade and > or =5 mitotic figures/50 HPF. Symplastic glomus tumor: Tumors with high nuclear grade in the absence of any other malignant feature. Glomus tumor of uncertain malignant potential: Tumors that lack criteria for malignant glomus tumor or symplastic glomus tumor but have high mitotic activity and superficial location only, or large size only, or deep location only. Glomangiomatosis: Tumors with histologic features of diffuse angiomatosis and excess glomus cells. Using this classification scheme, metastasis was observed in 38% of tumors fulfilling the criteria for malignancy. In contrast, metastatic disease was not seen in any specimen classified as symplastic glomus tumor, glomus tumor of uncertain malignant potential, or glomangiomatosis.

Glomus tumors: report on eleven cases and a review of the literature

INTRODUCTION

Glomus tumor is a well known pathology in hand surgery; in addition to sites in the upper limbs, it can also affect the lower limbs and develop in other parts of the body.

MATERIALS AND METHODS

Seven females and four males with glomus tumors underwent surgery between 1990 and 1998 at our hospital. These cases were retrospectively studied, and immunohistochemical staining was carried out for vimentin, factor VIII and CD34.

RESULTS

At the time of diagnosis, the mean age of the patients was 49 years, with a mean follow-up of 18.5 months. Regarding tumor site, there were six digital, one wrist, two neck and two lower limb locations. In this series, familial incidence was observed in two cases, i.e., two sisters with tumor occurrence at the same digital site. Tumor size varied from 0.2 to 5 cm. In agreement with the findings in the literature, the present results showed only a low incidence of locations other than in the upper and lower limbs. Moreover, no multiple locations or degenerative malignancy were observed, both of which are known to be rare. In all cases, the histological aspect of these tumors was typically benign. Immunohistochemical studies of the tumor cells were positive for anti-vimentin antibody in all cases, negative for anti-factor VIII in all cases and irregularly positive for anti-CD34 antibody.

DISCUSSION

It was not possible to confirm the specificity of the anti-CD34 antibody for glomus tumor in this series. The hypothesis of the endothelial origin of glomus tumor can probably be dismissed in the absence of the expression of anti-factor VIII and anti-CD34 antibodies.

Cutaneous vascular proliferation. Part II. Hyperplasias and benign neoplasms

This second part of our review about vascular proliferations summarizes the clinicopathologic features of the cutaneous vascular hyperplasias and benign neoplasms. Hyperplasias comprise a heterogeneous group of vascular proliferations that eventually show a tendency to regression. Angiolymphoid hyperplasia with eosinophilia is included within the group of hyperplasias because of its historical denomination and its reactive nature, probably as a consequence of an arteriovenous shunt, although usually the lesions do not regress. Pyogenic granuloma, bacillary angiomatosis, intravascular papillary endothelial hyperplasia, and pseudo-Kaposi's sarcoma qualify as vascular hyperplasias because they regress when the stimulus that initiated them is removed. Benign neoplasms form a large group of hemangiomas with distinctive clinicopathologic characteristics, although some of them are of recent description and may produce diagnostic difficulties. We classified cutaneous benign vascular neoplasms according to their cell lineage of differentiation, for example, endothelial, glomus cell, and pericytic differentiation. Subsequent categories are established according to the size of the involved vessels (capillaries, venules and arterioles, or veins and arteries) or the nature of the proliferating vessels (blood or lymphatic vessels). Capillary and cavernous hemangiomas have been the terms classically used to name the most common variants of benign vascular neoplasms (i.e., infantile hemangiomas), but they are not the most appropriate denominations for these lesions. First, these names are not contrasting terms. Furthermore, most of the socalled "cavernous" hemangiomas are not hemangiomas (neoplasms) at all, but venous malformations. The most important conceptual issue is that, at any point in time, a particular hemangioma has its own histopathologic pattern throughout the depth of the lesion. For these reasons, we classified hemangiomas into superficial and deep categories. Some of the lesions reviewed have been recently described in the literature, and they may histopathologically mimic lesions of Kaposi's sarcoma; these include targetoid hemosiderotic hemangioma, microvenular hemangioma, tufted hemangioma, glomeruloid hemangioma, kaposiform hemangioendothelioma, spindle-cell hemangioendothelioma, and benign lymphangioendothelioma. In each of these lesions, we update and emphasize those clinical and histopathologic features that are helpful for differential diagnosis with lesions of authentic Kaposi's sarcoma in any of its three stages of development (patch, plaque, or nodule).

Malignant glomus tumor: a case report and review of the literature

This report concerns a malignant glomus tumor, a rare soft tissue tumor that was examined immunohistochemically and ultrastructurally. It occurred in a 44-year-old male patient who had suffered from dull pain and stiffness in the right thigh for 10 months. Radiographic examination revealed a well-defined osteolytic lesion in the diaphysis of the right femur. Hypervascularity of the tumor was observed angiographically. Computed tomographic and magnetic resonance examinations showed an intramuscular mass invading the marrow space of the femur. Wide resection was performed after open biopsy. Histologically, round to polygonal tumor cells revealed a uniform appearance of round to ovoid nuclei with single large nucleoli and slightly eosinophilic cytoplasm, forming solid sheets of cells interrupted by vessels of varying size. A few mitotic figures and vascular invasion were observed. Immunohistochemically, vimentin and alpha-smooth muscle actin were stained intensely, and muscle actin was positive for tumor cells of the perivascular area. Tumor cells were negative for desmin, factor VIII-related antigen, S-100 protein, neurofilament, cytokeratin, and epithelial membrane antigen. Ultrastructurally, tumor cells were characterized by many cytoplasmic processes, pinocytotic vesicles, plasmalemmal dense plaques, and scattered microfilaments in the cytoplasm. Few cell junctions and focal basement membrane-like structures were observed. No recurrence or metastasis was noted 57 months after operation. This case was considered to be a malignant glomus tumor, that is, a glomangiosarcoma arising de novo.

Giant intravenous glomus tumor

We report a painful intravenous glomus tumor located in the right forearm of a 79-year-old woman. The tumor originated from the wall of a vein, protruded into its lumen and was completely excised. The largest dimension of the tumor occluding the vein was 14 cm. Tumor cells were characterized immunohistochemically by the presence of vimentin, alpha-smooth-muscle actin, and collagen IV. Intravascular spread of the glomus tumor is rare and has been described in the stomach and subcutaneous tissue. An entirely intravenous glomus tumor has been reported only three times. However, a huge intravenous growth as in our case appears never to have been reported. A review of the intravascular cases showed that the average age of presentation is 61.5 years (range 40-79 years) and the most frequent location is the forearm. Despite this intravascular growth, there is no evidence of aggressive clinical behavior, recurrence or metastasis. The pathologist must be aware of this variant of glomus tumor to avoid misdiagnosis and unnecessary additional treatments.