Introduction

Perivascular tumors are rare mesenchymal neoplasms of unclear line of differentiation, although most are presumed to be derived from pericytes or a modified perivascular cell, with very few articles published in the literature.

It is classified as benign, intermediate, and malignant. Benign and intermediate category encompasses glomus tumour, NOS (glomangioma, glomangiomyoma, glomangiomatosis, glomus tumour of uncertain malignant potential), myopericytoma (myofibromatosis, myofibroma, infantile myofibromatosis), and angioleiomyoma. The malignant category includes one entity, glomus tumour, malignant.[1]

Myopericytoma, angioleiomyoma, and glomus tumor all share a variety of histologic characteristics, such as a perivascular growth pattern. A glomus tumor is a soft tissue and subcutaneous tumor that has histological characteristics with the thermoregulatory glomus body. Glomus tumors commonly affect digits and have been found to have a recurrent MIR143–NOTCH fusion gene.[2] Glomangiomas are clinically different from glomus tumors as they occur in childhood and adolescence and are usually asymptomatic, often multifocal, and do not have a predilection for the subungual region.[3] Myopericytoma has some histologic resemblance to glomus tumor, but is most common on the lower extremities and is composed of eosinophilic tumor cells with clear smooth muscle differentiation and a whorled perivascular pattern.[4] Angioleiomyoma usually presents as a painful subcutaneous nodule, with a histological appearance of more differentiated smooth muscle cells, arranged in perivascular, fascicular, or cavernous growth patterns. There is well-recognized histologic overlap between these 3 tumors, leading some to use hybrid terms such as “glomangiopericytoma” and “glomangiomyoma.”

In this case series, we will be discussing five cases of perivascular tumours.

Case Series

Case 1

A 58-year-old female presented with cystic swelling over the lateral aspect of the right leg for 2 years. Fine needle aspiration was done, and a diagnosis of peripheral nerve sheath tumour was made. We received an excision specimen measuring 1.0x0.6x0.4 cm. The outer surface was globular and smooth. Cut section showed homogeneous gray white areas.

The microscopic examination revealed a well-circumscribed lesion displaying multilayered concentric growth around variably sized blood vessels comprising oval to spindle-shaped myoid cells embedded in fibrocollagenous stroma, and it was reported as Myopericytoma.

Case 2

A 29-year-old male presented with multiple painless swellings over the right flank measuring from 2cm-4cm. Clinical differential diagnosis was cutaneous hemangioma. Excision biopsy was done. We received a skin-covered gray-brown soft tissue piece measuring 4.5x3.0x1.0 cm. The outer surface showed a bosselated area measuring 2.0cm.

The microscopic examination showed tissue lined by stratified squamous epithelium. Underlying tissue showed a poorly circumscribed lesion comprising variably sized vessels surrounded by small clusters of glomus cells. Some areas showed the organoid architecture of tumour cells. These glomus cells have a round-shaped, punched out hyperchromatic nucleus with eosinophilic to pale cytoplasm. These tumour cells are extending into subcutaneous tissue. Features were suggestive of Glomangioma.(Figure 1 a and b)

Figure 1: (a) Gross image of multiple nodular glomangioma on the back (b) Photomicrograph of glomangioma of dilated veins surrounded by glomus cells (c) Photomicrograph of myofibroma showing light and dark areas (d) Photomicrograph of myofibroma shows light area showing hyalinised thick collagen bundles with plump spindle cells.

Case 3

A 52-year-old male presented with non-tender swelling over the right tibia for 1 year. Clinical differential diagnosis was a spindle cell lesion. Excision biopsy was done. We received a gray, white firm tissue piece measuring 1.5x0.9x0.6 cm. Cut section was gray white to gray-yellow with some hemorrhagic areas.

The microscopic examination revealed an unencapsulated lesion displaying numerous small, round to elongated and ectatic proliferative blood vessels surrounded by multilayered concentric growth of fusiform myoid cells having oval to spindle-shaped nuclei with bland chromatin. Foci of neutrophilic inflammatory cell infiltrate are seen. Features were in favour of Myopericytoma. (Figure 2)

Figure 2: Myopericytoma revealing (a) compressed blood vessels surrounded by spindled cells. (H& E, 10 X) (b) muscle from the walls of small-calibre vessels spins off into the stroma of the lesion. (H & E, 10 X). (c) and (d) fusiform cells demonstrating multilayered concentric growth around the vessels. (H & E, 40X).

Case 4

A 28-year-old male presented with non-tender swelling over the right medial malleolus for 2 years. Differential diagnosis of lipoma was given.

We received an excision specimen measuring 0.5x0.5x0.5 cm. The outer surface was globular and tan-brown.

Microscopic examination showed a well-circumscribed lesion containing numerous slit-like blood vessels forming a staghorn pattern surrounded concentrically by bland, oval to spindle-shaped myoid cells embedded in fibrocollagenous stroma. Diagnosis of Myopericytoma was made.

Case 5

A 34-year-old female presented with swelling over the interscapular region for 9 years. Clinical differential diagnoses were pedunculated cyst and sebaceous cyst.

We received a gray brown soft tissue piece measuring 2.0x1.5x0.7 cm. The outer surface is smooth. Cut section showed a well-circumscribed gray-white lesion with pinpoint hemorrhagic areas.

Microscopic examination showed tissue lined by stratified squamous epithelium. The underlying dermis showed a well-circumscribed lesion displaying dark and light staining areas. Dark areas comprised of plump oval to spindle shaped cells displaying elongated nuclei, minimal atypia, vesicular chromatin prominent nucleoli and scant eosinophilic cytoplasm arranged haphazardly and around numerous small vessels while light areas showed dense collagen bundles infiltrated by spindle shaped cells displaying cigar shaped nuclei, vesicular chromatin, prominent nucleoli and scant eosinophilic cytoplasm along with dense inflammatory cell infiltrate comprising of lymphocytes and histiocytes. The lumens of some vessels show the presence of foamy macrophages. Features were in favour of myofibroma. (Figure 1 c and d)

Discussion

Myopericytoma is a rare benign perivascular soft tissue neoplasm that has been acknowledged as a distinct entity in the past two decades. Our cases of myopericytoma and myofibroma both occurred in middle-aged to young adults with male predominance, which is similar to study done by Granter and colleagues [5] and Requena and colleagues[6]. Our findings support the view that MPC is a benign, mostly subcutaneous tumour that tends to affect distal extremities. However, it can arise at other sites, including the proximal extremities, head, and neck. Occasional cases have also been seen in skeletal muscle, bones (skull, vertebrae, ribs, femur, and tibia are most often affected), and other visceral organs. Clinically, myopericytoma predominantly presents as a solitary, well-demarcated, slow-growing, and non-painful palpable soft tissue mass present for several years.[7]

The differential diagnosis of MPC and MF varies with the predominant pattern/type of tumour. For tumours of the MPC type, biopsies from the central areas of the lesion may resemble various types of sarcomas, especially those composed of small round cells arranged in an HPC-like vascular pattern. The list of possible tumours includes Ewing’s sarcoma, which stains positively for CD99; poorly differentiated synovial sarcoma, which may have a biphasic growth pattern, and stains positively for epithelial membrane antigen, cytokeratin, bcl-2, and CD99; mesenchymal chondrosarcoma, which has islands of cartilage and stains positively for S100; phosphaturic mesenchymal tumour, which has a variety of patterns and is often associated with calcification and osteoclast-like giant cells [7]; and angiomatoid fibrous histiocytoma, which has angiomatoid spaces, hypercellularity as a result of proliferation of short spindle and/or ovoid cells, and a lymphoid infiltrate.[7] For tumours of the MF type the differential diagnosis includes smooth muscle tumour, which has fascicles of spindle shaped cells, cigar shaped nuclei, and is positive for SMA and desmin; inflammatory myofibroblastic tumour, which has a characteristic plasma cell infiltrate; nodular fasciitis, which typically involves a fascial plane, has a more prominent myxoid matrix, scattered chronic inflammatory cells, and extravasated erythrocytes; benign fibrous histiocytoma, which has a more pronounced storiform growth pattern, focal positive staining for SMA, and is usually positive for factor XIIIa; and neurofibroma, which is positive for S100; all lack an HPC pattern. For tumours that include glomoid cells, the main differential diagnosis is glomus tumour, including the glomangioma subtype. These have round to oval cells arranged eccentrically around vessels, with abundant eosinophilic cytoplasm, and in contrast to MPC, have a distinct cell border and lack an HPC-like vascular pattern.[8] Table 1 summarizes the characteristic features of various perivascular tumors.

A glomus tumor is a rare type of mesenchymal neoplasm that constitutes less than 2% of all soft tissue tumors. Multiplicity is seen in 10% and malignant glomus tumors are uncommon. Glomangiomas (Glomus venous malformations) are variants of glomus tumors characterized by hyperplasia of the glomus body, which is a component of the skin and a special arteriovenous anastomosis that contributes to the thermoregulatory function of the skin.

Glomangiomas are divided into a) regional type is usually blue-to-purple, partially compressible papules or nodules with a cobblestone-like appearance that are confined most commonly to the extremities b) disseminated variant is made up of multiple lesions that are distributed all over the body c) congenital plaque-like glomus tumors consist of either grouped papules that coalesce to form indurated plaques or clusters of discrete nodules. Our patient presented with the regional type of glomangioma that was limited to the right-sided flank region.

Most cases of glomangiomas are sporadic, but familial cases with autosomal dominant inheritance patterns have been reported. They usually manifest at birth or in childhood as purple skin lesions with a cobblestone pattern that develops over time. Our patient presented her lesions at 29 years of age with no family history of a similar condition.

Despite the presence of clear pathologic features, clinical diagnosis of glomangiomas continues to be a challenge. Boon et al.[9] stated that glomangiomas can be clinically distinguished from venous malformations based on the following characteristics: a cobblestone-like bluish-purple or dark blue lesion with slight hyperkeratosis, pain when the lesions are compressed, no phleboliths present, no reduction in size under external pressure or in a dependent position, and no pain during hormonal changes (such as puberty, menstruation, pregnancy, or the use of antiovulation drugs), unlike venous malformations.

Clinical differential diagnosis of glomangioma includes venous malformations, Blue Rubber Bleb Venous Syndrome (BRBNS), hemangiomas, myopericytoma, and Maffucci syndrome. Our patient’s initial provisional diagnosis was Hemangioma because of multiple red to purple nodules.[10]

References

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10. Abimiku PS, Okoro OE, Garba AY, Olarinoye GM, Oseze HU, Magaji D, et al. Cutaneous glomangiomas of the lower limb: A case report. Clin Oncol J. 2022;3(2):1–4.