a glomus body , or glomus apparatus , is a neuromyoarterial structure in the dermis layer of the skin , involved in body temperature regulation .
it consists of an arterio - venous shunt surrounded by a capsule of connective tissue . in response to sympathetic stimuli
, glomus body induces vasoconstriction in the shunt arterioles , controlling blood flow and skin temperature1,3,10,12 ) . glomus tumor or glomangioma is a kind of perivascular tumor and a rare benign neoplasm arising from the glomus body .
the vast majority of the tumors are found under the nail , on the fingertip or in the foot3,8,10,11 ) .
rarely , they may present in other body areas such as tympanic membrane , gastrointestinal organ , glans penis , or trachea4,8 ) . since normal human nervous system does not contain glomus bodies , glomus tumors affecting peripheral nerves are extremely rare .
the glomus tumor in the peripheral nerve is known as one of the mesenchymal tumors originating in the epineurium9,10,13 ) .
they are often associated with constant or episodic shooting pain that is generally unresponsive to conventional therapies .
the authors report a case of glomus tumor in the femoral nerve branch with a review of literature .
a 56-year - old man presented with severe lancinating pain at left anterior thigh for nine years , one year after accidentally bumping his left thigh to a tree .
he initially visited the other medical center where he was diagnosed with a mass lesion in the left thigh .
he was referred to the neurosurgery department for evaluation and surgical management . on physical examination , severe direct tenderness in the left anterior thigh was observed .
the range of motion in the extremities was full , but pain was provoked by physical irritation or by knee extension .
electromyography ( emg ) and nerve conduction velocity were consistent with left femoral neuropathy of moderate degree and chronic partial axonotmesis state .
the magnetic resonance images showed a well - defined , enhancing mass of 2.5 cm in diameter at left mid - thigh level , in between the rectus femoris , vastus laterlis , and vastus intermedius muscles ( fig .
the mass was formed along a muscular branch of the femoral nerve , and thus resembled a neurogenic tumor of femoral nerve branch , such as schwannoma .
the tan , pinkish white tumor was oval in shape with moderate vascularity , and well demarcated with the nerve tissue ( fig .
the cellular borders were sharply defined and angulated , and dilated vessels were surrounded by the tumor cells .
the immunohistochemical staining showed positive for smooth muscle antigen ( sma ) and negative for s-100 protein , and the ki-67 proliferative index was less than 1.0% ( fig .
a glomus tumors , a benign neoplasm arising from the glomus body , usually occurs in the subungal region , on the fingertip or in the foot3 ) .
the tumor was first described by hoyer in 1877 , while the first complete clinical description was given by barre and masson in 19245,9 ) .
glomus tumors are made up of afferent arterioles , anastomotic vessel , and collecting venules accompanying modified smooth - muscle cells .
anastomoses of the afferent arterioles with collecting veins are called sucquet - hoyer canals and the entire complex , with abundant unmyelinated nerve fibers , is surrounded by a collagenous capsule5,9,12 ) .
episodic pain , abrupt and lancinating in nature , is the most common symptom at presentation .
this pain can be provoked by pressure or cold and often unresponsive to conventional therapies .
interruption of afferent blood flow may be effective , which is the basis of the tourniquet test3,5 ) .
multiple variant is not common , and approximately 10% of these tumors occur in multiples4,6,9 ) .
an association with neurofibromatosis type 1 has also been rarely mentioned in multiple variant glomus tumors12 ) .
glomus tumor associated with apparent peripheral nerve is extremely exceptional , despite normal glomus bodies have a microanatomical connection with small , unmyelinated nerve fibers14 ) . so far ,
only nine cases including the present case have been documented to our knowledge1,2,7,9,13 - 16 ) .
the tumors have affected various sites such as the common peroneal nerve16 ) , the radial nerve13 ) , the sciatic nerve9 ) , the tibial nerve15 ) , a digital branch of the ulnar nerve7 ) , a dermal nerve in the shoulder1 ) , the median nerve9 ) , and the sural nerve2 ) .
the present case is the first report of a glomus tumor associated with the femoral nerve branch .
all lesions occurred in adults : six in male patients and three in female patients .
the nine tumors reported ranged from 1 mm to 7 cm in size and had benign clinical and pathological nature .
all the patients clinically improved with surgical excision and no evidence of recurrence was reported .
the rare occurrence of glomus tumors in nerves where normal glomus bodies have not been found can be approached by a number of theories7 ) .
first , the tumor might infiltrate from an extraneural tissue such as accompanying vessels by direct extension .
second hypothesis is that tumors are developed from a possible normal intraneural glomus body or ectopic glomus cells , but such histological findings have never been described in nerves so far .
the third possibility is that the tumor developed through differentiation from unspecialized perivascular wall , or pericytes in particular .
pericytes are also modified smooth - muscle cells , widely distributed around small - sized vessels like vasa nervorum .
also , smooth - muscle cell and glomus tumor cell show a resemblance in immunophenotype study ( sma+ , collagen iv+ , s100- , and epithelial membrane antigen ; ema- ) . the differentiation of pericytes into tumor cells can be a potential explanation for the origin of glomus tumors where glomus body do not exist in general3,5 - 8,10,12 ) . in this case , we are in favor of first and the third hypotheses , because the tumor was obviously connected to a small vessel and the tumor was discrete to the associated neural tissue .
when a patient complains severe lancinating pain aggravated by exercise or physical irritation , and especially has history of trauma as is this case , surgeons easily consider the diagnosis of painful neuroma
when presenting at an uncommon site such as a nerve , other entities including a schwannoma , a meningioma , an epithelioid leiomyosarcoma , a metastatic melanoma , a carcinoma or a glomus tumor should be considered as differential diagnosis10 ) .
mere medication and loose observation may be catastrophic , and image study and surgical confirmation must be considered at an early stage .
operative excision has benefits in both diagnosis and curative treatment of the tumor affecting peripheral nerves . although glomus tumors are closely associated with the functioning peripheral nerves , complete surgical excision can be achieved without difficulty thorough microsurgical techniques . according to the literatures along with our experience on a glomus tumor in the peripheral nerve , a nerve - sparing surgical excision is the curative treatment of choice .
when a tumor is deeply seated between muscles and is without a palpable mass , it can be hard to locate the exact lesion site . at first surgery in the present case ,
the authors were able to remove the tumor successfully with the aid of intraoperative ultrasonography .
intraoperative emg monitoring may also be helpful , but it was omitted in the present case because the operation was performed under spinal anesthesia .
the debilitating lancinating pain was resolved and no recurrence was seen after total resection of the tumor as were the reported cases .
a glomus tumor can be encountered at an uncommon site , such as a peripheral nerve . severe shooting pain and pressure tenderness are characteristic clinical features .
 the glomus tumor of the peripheral nerve is one of the mesenchymal tumors originating in the epineurium , and is extremely rare . 
 a 56-year - old man presented complaining of lancinating pain on the left thigh , which was provoked by pressure or exercise . 
 subsequent image study revealed a mass in the femoral nerve . 
 total surgical excision with the aid of intraoperative ultrasonography was performed and the pain was successfully controlled . 
 the authors report an unusual case of a patient diagnosed with glomus tumor in peripheral nerve , with a review of the clinical features , imaging , and pathological findings . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION