2015, Volume 31, Number 3, Page(s) 211-214
Symplastic Glomus Tumor
Fevziye KABUKÇUOĞLU1, Hanife ÖZKAYALAR1, Damlanur SAKIZ1, Yavuz KABUKÇUOĞLU2
1Department of Medical Pathology, Şişli Etfal Education and Research Hospital, İSTANBUL, TURKEY
2Department of Orthopaedics and Traumatology, Metin Sabancı Baltalimanı Bone Diseases Training and Research Hospital, İSTANBUL, TURKEY
Keywords: Glomus tumor, Differential diagnosis, Metastasis
Glomus tumors showing nuclear pleomorphism without any other
malignant features have been defined as symplastic glomus tumors.
This type of glomus tumor is rarely encountered. Another case of
symplastic glomus tumor is described in this study. A 37-year-old
woman referred to the hospital with the complaint of a palpable
tender nodule on the fourth finger tip of her left hand. The lesion had
been present for about a year and aggravation of tenderness upon cold
exposure was conspicuous. It was a 0.5 cm well circumscribed lesion
with round to cuboidal epithelioid cells showing high grade nuclear
pleomorphism. Nests of cells more uniform in shape and showing
punched out nucleus representative of typical glomus tumor could
also be observed. Immunohistochemical study showed expression of
smooth muscle actin, caldesmon and vimentin. Ki-67 labeling index
was undetectable. Investment of tumor cells was shown by type IV
collagen. In contrast to its atypical cellular morphology, symplastic
glomus tumor clinically behaves benign, and it is important to
differentiate it from malignant glomus tumor as well as other primary
or metastatic malignant tumors.
Glomus tumors are mesenchymal neoplasms composed of
cells closely resembling the modified smooth muscle cells of
the normal glomus body which is a specialized arteriovenous
shunt involved in temperature regulation. They constitute
less than 2% of the soft tissue tumors1,2
. The majority
of these tumors are small red blue nodules that occur in
the dermis or subcutis of the distal extremities, particularly
in the subungual region, the hand, the wrist and the foot.
A long history of pain especially with exposure to cold or
minor tactile stimulation is characteristic3-5
the features of the tumor are distinctive, diagnosis can be
occasionally conflicting because of unusual features such as
large size, deep soft tissue or visceral location, infiltrative
growth pattern, pleomorphism and mitotic activity6,7
Rare examples of malignant glomus tumors have been reported, while some have been classified as glomus tumor
of uncertain malignant potential8-10
. Furthermore, a
form of glomus tumor that shows striking nuclear atypia
without any other malignant features has been designated
as symplastic glomus tumor6
. There have been only few
case reports of this type of glomus tumor presented in the
literature up to date11-13
. The authors report another
example of the symplastic glomus tumor in the left fourth
finger tip of a 37-year-old woman.
A 37-year-old woman presented with the complaint of
a palpable tender nodule on the fourth finger tip of her
left hand. The mass was 0.5 cm in diameter and had been
present for about a year. The patient emphasized aggravation
of tenderness upon cold exposure. There was no history
of trauma. Gross examination of the excised material showed a bluish red nodule measuring 0.5x0.3x0.2cm.
Histopathological examination showed a well circumscribed
tumor involving the dermis and subcutaneous tissue.
The tumor was composed of capillary sized blood vessels
surrounded by a solid proliferation of round to cuboidal
epithelioid cells with centrally placed, sharply punched
out round nucleus and eosinophilic cytoplasm. Most of
the cells showed marked nuclear pleomorphism and atypia
with occasional bizarre nuclei. Intranuclear inclusions
were noted in some of the pleomorphic cells. Nests of
typical glomus cells could be observed next to atypical
areas (Figure 1A,B
). No mitosis or necrosis was observed.
The stroma between the tumor islands was hyalinized
with focal myxoid change. The surgical margins were free
of tumor. Immunohistochemically the tumor cells were
positive for smooth muscle actin, caldesmon and vimentin
). CD34 showed focal staining. Investment of
tumor cells was shown by type IV collagen (Figure 2C
No staining was observed for CK, HMB45, Melan A and
S100. Ki67 labeling index was less than 1%. S100 staining
showed numerous nerve structures transversing the tumor.
The case was interpreted as symplastic glomus tumor. There
was no recurrence in one year follow-up of the patient.
Click Here to Zoom
|Figure 1: A) Tumor composed of cells showing perivascular orientation and pronounced pleomorphism. A nest of typical glomus cells
is noted at the left (H&E, x200). B) Round to cuboidal epithelioid cells with central punched out nuclei showing high grade nuclear
pleomorphism. (H&E, x400).
Click Here to Zoom
|Figure 2: A) The expression of smooth muscle actin by tumor
cells (SMA; x400). B) The expression of caldesmon by tumor cells
(Caldesmon; x400). C) The investment of tumor cells by type IV
collagen (Type IV collagen; x400).
Glomus tumors are quite distinctive with their characteristic
morphology, location and symptoms, but rarely they may
display unusual clinical or histopathological features. Rare
cases have been interpreted as malignant glomus tumor on
the basis of nuclear atypia, necrosis and mitotic activity8-10
. The largest series of atypical glomus tumors has been constituted by Folpe et al6
. Criteria for malignancy have
been defined based on the analysis of 52 cases for size,
depth, growth pattern, cellularity, nuclear grade, number
of mitotic figures, vascular space involvement and necrosis.
They have suggested the term “malignant glomus tumor”
to be reserved for tumors with a marked risk of metastasis.
Such lesions fulfill at least one of the following: deep
location and size more than 2cm, or presence of atypical
mitotic figures or marked nuclear atypia with mitotic
In Folpe's study, glomus tumors not fulfilling criteria for
malignancy but having at least one atypical feature other
than nuclear pleomorphism were categorized as “glomus
tumors of uncertain malignant potential”6. Tumors in this
category are superficial tumors with high mitotic activity
or they are large or deep. Glomangiomatosis was used for
tumors with diffuse angiomatosis and excess glomus cells.
Finally, the term “symplastic glomus tumor” was proposed
for glomus tumors with high nuclear grade in the absence
of any other malignant feature. Nine of the cases were
classified as symplastic glomus tumor in the series. Two of
them showed recurrence and none of them metastasized.
They concluded that these tumors were benign similar to
ordinary glomus tumors.
The marked nuclear atypia in glomus tumors is similar
to that seen in some benign mesenchymal tumors of
long duration, especially uterine leiomyoma and ancient
schwannoma. These tumors behave like ordinary
leiomyomas and schwannomas, therefore the nuclear atypia
has been accepted as a degenerative change1,6,14.
The tumor cells of the presented case showed striking
nuclear atypia, some with bizarre nuclei. Although the
pleomorphism and the epithelioid configuration of the
tumor were alarming at the initial evaluation, malignancy
was not in the foreground because neither mitotic activity
nor necrosis was present and Ki-67 labeling index showed
that the proliferative activity was undetectable. While
typical glomus tumor areas were only focal, the punched
out appearance of tumor cells could be identified even at
the atypical areas. Type IV collagen pattern and smooth
muscle actin staining were consistent with symplastic
glomus tumor. The morphology together with the clinical
symptoms confirmed the diagnosis.
The evaluation of symplastic glomus tumors needs careful
histopathological examination1,5,6. Marked nuclear
atypia of the tumor may be reminiscent of a malignant
tumor. Epithelioid appearance of the tumor may be
misleading. While the identification of areas of typical
glomus tumor is the most important clue to the diagnosis,
these areas may be minimal or absent in some cases. The
branching capillaries and the perivascular arrangement
of tumor cells should be noted. Immunohistochemical
study showing smooth muscle actin expression and type
IV collagen, a constituent of basal lamina, outlining the
cells are the most beneficial in histopathological diagnosis
especially when the typical glomus tumor areas are not
distinctive1. Lack of expression by cytokeratins helps
to eliminate a primary or a metastatic epithelial tumor
and adnexial tumors. HMB45 and S100 negativity allow
distinction from malignant melanoma. Despite its atypical
morphology, symptoms and location are quite typical in
most cases of symplastic glomus tumor, thus it is important
to get thorough clinical history.
Symplastic glomus tumor is considered benign with
occasional recurrences due to incomplete excision.
Recognition of this rare morphologic deviation is critical,
as the marked atypia can lead to an incorrect diagnosis of
malignancy and overtreatment.
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