Title: Mesectodermal leiomyoma: a unique morphology, revisiting the embryogenesis
Running title: Mesectodermal leiomyoma
Manuscript Type: Case Report
Authors:

Dr. Kaushik Majumdar, MD, DNB (Senior Research Associate)

Dr. Shramana Mandal*, MD, DNB (Assistant Professor)

Prof. Ravindra K Saran, MD, DNB (Professor)

Dr Sushil kumar1 MS (Professor)
INSTITUTE:

Department of Pathology and Ophalmology, G B Pant Hospital and Guru Nanak Eye centre,
Jawaharlal Nehru Marg, New Delhi 110002, India.
Corresponding author:
* Dr Shramana Mandal, MD, DNB (Pathology)
Assistant Professor, Dept of Pathology, Academic Block,
G B Pant Hospital, Jawaharlal Nehru Marg, New Delhi -110002 INDIA
Phone: 91- 9718599072 (Mobile)
E mail: [email protected]
Abstract
Mesectodermal leiomyoma connotes a tumor originating from the smooth muscle of the ciliary
body, a mesodermal tissue derived embryologically from the neural crest (ectoderm). The tumor
recapitulates its ancestral embrogenic pathway, bearing the histomorphology quite different from
the usual fascicular architecture comprising of myogenic spindle cells of a leiomyoma
originating from the smooth muscles at other locations. We present a case of 19 year-old female
presenting with a history of progressive loss of vision in the left eye for last 8-10 months.
Histopathologic features were those of leiomyoma of the ciliary body with strong
immunohistochemical expression of smooth muscle actin.
Thus, leiomyomas arising from the ciliary body are rare specialized tumors, recapitulating the
mesectodermal ancestry. Early diagnosis and timely surgical intervention is necessary to prevent
complications.
Introduction
Leiomyoma of the ciliary body is a rare benign smooth muscle tumor bearing a unique
morphology, more closely appearing as glial or neural, rather than myogenic origin. First
reported as an unusual ‘hybrid neurogenic-myogenic’ tumor by Jacobiec et al in 1977, the term
mesectodermal leiomyoma was introduced to connote a tumor originating from the smooth
muscle of the ciliary body, a mesodermal tissue derived embryologically from the neural crest
(ectoderm)1.
Hence the tumor recapitulates its ancestral embrogenic pathway, bearing the
histomorphology quite different from the usual fascicular architecture comprising of myogenic
spindle cells of a leiomyoma originating from the smooth muscles at other locations. 2-6
Case Report
A 19 year-old female presented with a history of progressive loss of vision in the left eye for last
8-10 months. It was associated with pain in the eye. Ophthalmologic examination showed a
large vascularised mass measuring 2.5x2x2 cm arising from the anterior uvea. The lens was
displaced anteriorly by the tumor. Enucleation of the left eye was performed due to the large size
of the tumor and loss of vision, considering the possibility of malignancy.
Grossly, a relatively well demarcated round to oval mass lesion was observed in the posterior
chamber of the eye measuring 2x1.2x1 cm. The cut surface of the tumor showed homogeneous
gray white appearance, with firm to hard consistency (figure 1a). A part of optic nerve was also
identified.
Microscopically, a well circumscribed tumor was observed in the posterior chamber in close
relation to the normal ciliary smooth muscle, covered by the ciliary epithelium and pushing the
lens anteriorly. The tumor consisted of sheets of polygonal cells, with a tendency to become
spindle shaped towards the base of the tumor. The tumor cells had central round to oval nuclei,
fine chromatin; atypia and mitotic figures were not seen. The cells at the center of the lesion had
moderate eosinophilic cytoplasm with indistinct borders and slender cellular processes yielding a
fibrillary background (figure 1b,c). Massons trichrome (MT) showed presence of muscle. On
immunohistochemistry (IHC) the cells expressed SMA and vimentin and were negative for S100, neurofilament protein (NFP) and GFAP. An overall diagnosis of a large mesectodermal
leiomyoma arising from the ciliary body was considered.
Discussion
Mesectodermal leiomyoma has a predilection for young women, with tumor size usually ranging
from 0.4 to 1.6 cm.2,3 On transillumination, it usually transmits light well, whereas most
melanomas cast a shadow.7 It is often associated with sublaxation of lens or retinal detachment
with fluid in the subretinal space.3 On ultrasonographic examination the mass appear
heterogeneously hyperechoic; on MR imaging, the mass usually appear hyper intense to contra
lateral vitreous on T1-weighted images and hypointense on T2-weighted images, with contrast
enhancement. These MR imaging features are nonspecific, and can also be observed in other
more common intraocular tumors, such as retinoblastoma, medulloepitheioma, melanoma, and
retinal or choroidal hemangioma.2,3,7
Mesectodermal leiomyoma usually manifests dual (myogenic and neurogenic) histomorphology
and immunophenotype. The eosinophilic fibrillary appearance on histology reminiscent of glial
morphology is produced by the tangled cytoplasmic processes, which was initially described as
intracytoplasmic ‘myoglial’ filaments.8 On electron microscopy these correspond to thin
filaments with focal cytoplasmic densities.2 Hence histological differential diagnoses include
glioma, peripheral nerve tumor, amelanotic nevus, amelanotic melanoma or paraganglioma.2,9 In
this case the differential diagnosis considered were glial tumor or a smooth muscle tumor.
The neural crest cells derived from the neuroectoderm are capable of multipotential
differentiation, contributing to the formation of bone, cartilage, connective tissue, and smooth
muscle in the head and neck region. These neural crest derived mesodermal elements have been
termed 'mesectoderm'. Smooth muscle of the iris and ciliary body, derived from this
mesectoderm, is thus embryologically different from smooth muscles located in other parts of the
body. Hence, the unusual neural or glial appearance of mesectodermal leiomyoma originating
from ciliary body recapitulates the embryonic ancestry.1,3,9 leiomyomas are commonly seen in
the genitourinary and gastrointestinal tracts. These tumours can also be found in the nipple and
subareolar region and in some extremely rare cases in the breast parenchyma.10
Most reports suggest early intervention and local resection of the tumor, while enucleation is
reserved for large tumors with appearance of complications. Only occasional case may develop
sarcomatous change.3
To conclude, leiomyomas arising from the ciliary body are rare specialized tumors,
recapitulating the mesectodermal ancestry. Hence a dual myogenic and neurogenic histological
and immunohistochemical phenotype in anterior uveal tumors is important to arrive at the
diagnosis, especially in centers where ultrastructural facility is not available. Early surgical
intervention is necessary to prevent complications and avoid enucleation.
References:
1. Jacobiec FA, Font RL, Tso MO, Zimmerman LE. Mesectodermal leiomyoma of the ciliary
body: a tumor of presumed neural crest origin. Cancer 1977; 39:2102–2113
2. Park SH, Lee JH, Chae YS, Kim CH. Recurrent mesectodermal leiomyoma of the ciliary
body: a case report. J Korean Med Sci 2003; 18:614-7.
3. Park SW, Kim HJ, Chin HS, Tae KS, Han JY. Mesectodermal leiomyosarcoma of
the ciliary body. AJNR Am J Neuroradiol 2003; 24:1765-8.
4. Koletsa T, Karayannopoulou G, Dereklis D, Vasileiadis I, Papadimitriou CS, Hytiroglou P.
Mesectodermal leiomyoma of the ciliary body: report of a case and review of the literature.
Pathol Res Pract 2009; 205:125-30.
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cases of ciliary body mesectodermal leiomyoma: unique expression of neural markers.
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leiomyoma. Arch Ophthalmol 1994; 112: 521–528
8. Noor Sunba MS, Rahi AH, Garner A, Alexander RA, Morgan G. Tumours of the anterior
uvea. III. Oxytalan fibres in the differential diagnosis of leiomyoma and malignant melanoma
of the iris. Br J Ophthalmol 1980; 64:867-74.
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body: case report. Br J Ophthalmol 1989; 73:12-8.
10. Mandal S, Dhingra K, Khurana N. Parenchymal leiomyoma of breast, mimicking
cystosarcoma phylloides.
Legends
Figure 1a: Shows a mass lesion in the posterior chamber of the eye with homogeneous
gray white appearance and firm to hard consistency
1b : Shows tumor in the posterior chamber in close relation to the normal ciliary smooth
muscle, covered by the ciliary epithelium. [HE x 200]
1c : The tumor consisted of sheets of polygonal to spindled cells. Some cells have
moderate eosinophilic cytoplasm with indistinct borders and slender cellular processes
yielding a fibrillary background. [HE x 200]
Figure 2a: Tumour cells showing positivity for MT [MT x200]
2b: Tumour cells showing Smooth muscle actin positivity (IHC x200)