Leiomyoma of the Ciliary Body

L E I O M Y O M A OF T H E CILIARY

BODY

ELECTRON MICROSCOPIC VERIFICATION SAM

L . MEYER, M . D . , * B E N S . F I N E , M . D . , RAMON L . FONT, M . D . AND

LORENZ E . Z I M M E R M A N , M . D . Washington, D.C.

Leiomyomas, although fairly common'Ul the

uterus

and gastrointestinal

istics that help in its identification. These are

tract, are

(1)

among the rarest of primary intraocular neo-

many intracytoplasmic bundles of paral-

lel filaments ; ( 2 ) oval to fusiform dense areas

plasms. Occasional case reports of these tu-

scattered throughout the filamentous portions

mors have appeared in the literature since

of

the mid-1800's. Few of the earlier reported

densities adjacent to the plasmalemma; ( 4 )

cases of leiomyoma of the ciliary body, how-

myriad small vesicular indentations of the

ever, are acceptable by the present criteria

plasmalemma ("caveolae") between the latter

for

diagnosis.

the cytoplasm; ( 3 ) similar cytoplasmic

dense patches; and ( 5 ) a basement membrane that completely invests the cell except

Blodi, in a critical review of the world 1

literature in 1950, found 10 reported cases

for

of

small areas where attachments or close

leiomyoma of the ciliary body, none of

approximations to adjacent cells occur. There-

which he could accept unequivocally. The

fore electron microscopic examination of a

case he presented at that time was the first

smooth muscle tumor could be very revealing.

that fulfilled all the following histologic re-

At

quirements for this tumor: ( 1 ) interlacing, tightly

packed bundles

of

ogy

spindle-shaped

the Armed Forces Institute of Patholthere are seven tumors of the ciliary

body in the Registry of Ophthalmic Pathol-

cells with little or no collagenous stroma;

ogy

(2)

croscopic diagnosis of leiomyoma. Only one

oval nuclei with blunted ends that may

that satisfy the criteria for the light mi-

palisade; ( 3 ) cells possessing a moderate

of

amount of fibrillar eosinophilic cytoplasm;

microscope, because no wet tissue was avail-

and

these tumors was studied by the electron

( 4 ) intracellular fibrils that stain with

able on the others. This report records all

Masson's trichrome or with phosphotung-

observations made in the study of this case.

stic-acid hematoxylin ( P T A H ) . Since Blodi's paper, three additional case reports have

CASE REPORT

been published, in all of which the tumor

A 50-year-old Caucasian woman ( A F I P Accession No. 1261242) had noticed blurring of vision in her right eye for six to seven months. Examination of her eyes revealed corrected visual acuity of 20/30 in the right eye and 20/20 in the left. The intraocular tension was within normal limits bilaterally. Ophthalmoscopy revealed a large, dark mass arising from the ciliary body nasally, with a slight iridodialysis "opposite the site of the lesion." A diagnosis of malignant melanoma was made, an opinion supported by a second ophthalmologist, and the eye was enucleated.

fulfilled the above criteria.

2-4

The typical smooth muscle cell (fig. 1) has several distinctive ultrastructtiral character-

From the Registry of Ophthalmic Pathology, Armed Forces Institute of Pathology, and the Department of Ophthalmology, the George Washington University Medical Center, Washington, D.C. This study was supported in part by U S P H S research grants NB-Ó7774 and NB-05575 and Training Grant NB-5379, from the National Institute of Neurological Diseases and Blindness. * Special Fellow in Ophthalmic Pathology, National Institute of Neurological Diseases and Blindness, NIH, at the A F I P . Reprint requests to Armed Forces Institute of Pathology, Washington, D.C. 20305 (Dr. Zimmerman). 1061

PATHOLOGIC

FINDINGS

Macroscopically the specimen consisted of a soft, formalin-fixed right eye measuring 24.5 X 24.5 X 24.5 mm with 11 mm of optic nerve attached. On transillumination a roughly circular shadow, measuring 13.5 X 15 mm, was seen from the 2- to 4-o'clock positions in the area of the ciliary body nasally. After the eye was opened in the horizontal plane, a sharply demarcated white tumor measuring

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Fig. 1 (Meyer, Fine, Font, and Zimmerman). A sample of normal ciliary muscle to show the components of a normal smooth muscle cell. The cell possesses an almost completely investing basement membrane ( B M ) , myriad surface-connected caveolae ( V ) , intracellular filaments ( F ) , and their associated densities ( D ) , a number of which are also present along the surface membrane of the cell ( D i ) . The remainder of the cell organelles are arranged along the poles of the cell nucleus ( N ) . ( X 16,800, A F I P Neg. 68-5246-6.) 6.5 mm in height and 9 mm in length was seen in the ciliary body nasally. There was no evidence of extraocular extension of the tumor. The central block of tissue containing the bulk of the tumor was processed for paraffin sections, and a small piece of tumor from one calotte was removed for electron microscopy (fig. 2 ) . The tissue removed for electron microscopic study was prepared by methods reported elsewhere. Microscopically most of the anterior segment was not remarkable, but arising from the ciliary body nasally there was a nonpigmented, sharply demarcated, globoid tumor (fig. 3 ) . It was composed of spindle-shaped cells containing rod-shaped nuclei with blunted ends and of fibrillar acidophilic cytoplasm (figs. 4 and 5 ) . Special stains (Masson's trichrome, P T A H ) revealed longitudinal fibrils within the cytoplasm of the tumor cells. Anteriorly the fibers of the ciliary muscle were observed to blend into the tumor with imperceptible change in staining characteristics between normal muscle and tumor (fig. 4 ) . The posterior edge of the tumor was sharply demarcated, and there was no infiltration of the adjacent uvea (fig. 3 ) . Special stains for melanin and iron were negative. The remainder of the ciliary body, the lens, and the vitreous were 5

not remarkable. The peripheral retina overlying the tumor had undergone cystic degenerative changes, with the formation of chorioretinal adhesions. There was a small amount of eosinophilic subretinal exudate in one area adjacent to the tumor. There were also a few small collections of exudate within the outer plexiform layer of the retina. With the exception of choroidal congestion, the remainder of the posterior segment was not remarkable. ELECTRON MICROSCOPY

Even though the specimen was fixed initially in 10% buffered formalin, sufficient cellular detail remained to permit an electron microscopic characterization of the tumor cells. The cells were cut in longitudinal, oblique, and cross sections (fig. 6 ) , and almost all appeared identical. They contained large aggregates of filaments oriented along the long axis of the cells (figs. 6-8). Scattered throughout these bundles of filaments were dense patchy areas, present also along the plasmalemma. In addition, the plasmalemma exhibited myriad vesicular indentations or caveolae between these dense areas (inset, fig. 6 ) . Basement membrane material was observed to invest each individual cell where the plasmalemma was adequately preserved and properly sec-

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tioned (figs. 6 to 8 ) . Where a cell was appropriately sectioned longitudinally, the cytoplasmic filaments and their dense patches were seen to occupy the cell periphery (fig. 6 ) , while the remainder of the cell organelles were clustered axially about the poles of the cell nucleus (fig. 8 ) . In some areas of the tumor there were large aggregates of collagen fibrils that branched in a dendritic pattern, separating large groups of cells (fig. 9 ) . A peculiar banded patch of basement membrane material in close approximation to several disrupted smooth muscle cells was noted in one section (fig. 10). DISCUSSION

The diagnosis of a primary leiomyomatous tumor of the ciliary body is usually difficult to make by light microscopy. Tumors

Fig. 3 (Meyer, Fine, Font, and Zimmerman). Leiomyoma of the ciliary body. Note the distinct posterior edge with no infiltration of adjacent uvea. (Hematoxylin-eosin, X3.5, A F I P Neg. 67-11611.)

Fig. 2 (Meyer, Fine, Font, and Zimmerman). Low-power view of the cap section showing the area where the tumor for the electron microscopic study was taken. ( X 4 , A F I P Neg. 67-11248-2.)

Fig. 4 (Meyer, Fine, Font, and Zimmerman). Anterior edge of the tumor showing the remaining small amount of normal ciliary muscle flowing into the tumor. (Hematoxvlin-eosin, reduced from X 4 0 , A F I P Neg. 67-11603.)

that must be included in the differential diagnosis are ( 1 ) neurofibroma, ( 2 ) amelanotic spindle cell malignant melanoma, and ( 3 ) neurilemoma (schwannoma). In addition to the aforementioned criteria for diagnosis of a leiomyoma, it must be remembered that the Masson trichrome and P T A H stains do not distinguish myofibrils from neurofibrils. 6

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Fig. 7 (Meyer, Fine, Font, and Zimmerman). Sample of tumor from formalin-fixed tissue. There is considerable disruption of the cells, but the intracellular filaments ( F ) with their associated densities ( D ) characteristic of mature smooth muscle cells are clearly seen. A basement membrane ( B M ) surrounds the surface plasma membrane of the cell. Collagen fibrils ( C ) "negatively stained" by the embedding ground substance lie between clusters of cells. ( X 18,000, A F I P Neg. 68-5246-4.) Inset: Sample of presumably normal ciliary muscle taken from the periphery of the tumor. Intracellular filaments and densities are seen under the same conditions of fixation, which—although useful for purposes of cell identification in this specimen—is less than optimum for good preservation of the entire cell. Smooth muscle cell basement membrane ( B M ) . (Xl7,000, A F I P Neg. 68-5246-4.) 7?///

r

Fig. 5 (Meyer, Fine, Font, and Zimmerman). High-power view of a representative portion of the tumor illustrating the fibrillar nature of the cells, their parallel orientation, and the rod-shaped nuclei. (Hematoxylin-eosin, reduced from X 1,040, A F I P Neg. 68-2837.)

Fig. 6 (Meyer, Fine, Font, and Zimmerman). The nuclei ( N ) of two adjacent smooth muscle cells containing longitudinally oriented dense filaments and associated patches ( D ) are seen here. Caveolae are present along the surface plasma membrane where the latter has been adequately preserved and properly sectioned (free arrows). These myriad surface-connected caveolae or "micropinocytotic vesicles" in the area indicated by arrows are better seen in the inset ( X 18,000). (Large micrograph X 12,600. A F I P Neg. 68-5246-7.)

\\\\\ V //i/i r~

Fig. 8 (Meyer, Fine, Font, and Zimmerman). Another sample of tumor to show the orientation and localization of the cell organelles along the poles of the nucleus ( N ) is seen in the middle cell of three cells. Mitochondria ( M ) and many segments of granular endoplasmic reticulum ( E R ) can still be recognized. The caveolae-studded surface membranes of two adjacent cells separated by basement membranes is indicated by the free arrows. ( X 16,500, A F I P Neg. 68-5246-2.)

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Fig. 9 (Meyer, Fine, Font, and Zimmerman). Large branching aggregates of collagen fibrils embedded in ground substance ( C O ) permeate much of the tumor between bundles of cells. X 18,000, A F I P Neg. 68-5246-1.) The adjacent "debris" consists mostly of disrupted smooth muscle cells. The inset in the lower left shows a cross section of the embedded collagen bundle. ( X 18,000. A F I P Xeg. 68-5246-1.) The inset in the upper right is a thin section (1.5 micron) light micrograph of Epon-embedded paraphenylendiamine-stained tissue to show the prominent dendritic patterns produced in this tumor by the bundles of collagen seen in the electron micrograph. (X300, A F I P Neg. 68-593.) —

Fig. 11 (Meyer, Fine, Font, and Zimmerman). A sample of nonpigmented malignant melanoma of the ciliary body. The cells are not highly oriented. Melanin granules are absent, and the cells have no basement membrane. Intracellular filaments or their associated dense patches are lacking. Surface-connected caveolae are also lacking. Extracellular collagen formation is lacking in this particular tumor sample. ( X 18,000, A F I P Xeg. 68-5246-5.) Therefore,

if

any diagnosis

of

intraocular

leiomyoma is made with heavy reliance

on

well-differentiated

smooth

muscle

were

electron

microscopy,

studied

by

tumor it

these stains, some small doubt remains as to

should be easy to recognize, since the dis-

its accuracy. It appears, however, that if a

tinctive

ultrastructural

characteristics

of

—

Fig. 10 (Meyer, Fine, Font, and Zimmerman). Many of the smooth muscle cells are disrupted but may be recognized by their cytoplasmic filaments ( F ) and associated dense patches ( D ) as well as by segments of caveolac-studded and basement membrane-coated plasma membranes ( P M ) . Bands of embedded collagen fibrils ( C O ) are present, as well as large patches of banded basement membrane material ( B . B M ) . The latter material may be observed in both normal and abnormal tissues. ( X 18,000, A F I P Neg. 68-5246-3.)

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normal smooth muscle are well known. The results of the electron microscopic study here reveal that this tumor is composed of cells in which all the typical fine-structural characteristics of smooth muscle can be identified. On this basis we believe this is good evidence that this tumor is a true leiomyoma of the ciliary body. We have included an electron micrograph (fig. 11) of a sample of nonpigmented malignant melanoma of the ciliary body for comparison. The melanoma cells of this tumor possess no dense bodies characteristic of melanin or caveolae on the plasmalemma, and the cells are clearly devoid of a basement membrane. In addition, the cytoplasm of this tumor cell lacks any structure resembling myofibrils or dense cytoplasmic patches characteristic of smooth muscle cells. 7

It is more difficult to rule neurofibroma and neurilemoma out of the diagnosis. A normal Schwann cell resembles closely the above description of a nonpigmented melanoma cell. It also lacks the large numbers of intracellular filaments, associated dense patches, and myriad surface-connected vesicles. Unlike the melanoma cell, the Schwann cell does possess a basement membrane in both its normal and neoplastic states. 8

A neurofibroma would presumably contain both fibrous and neural elements. Fibroblasts, although containing cytoplasmic filaments, lack the cytoplasmic dense patches and a basement membrane. The cytoplasmic filaments of neural elements, when fixed in aldehydes, are altered to form neurotubules and so become easily distinguishable from other filament-bearing cells. ' No cells containing cytoplasmic tubules were seen in this formaldehyde-fixed tumor. Therefore, the electron microscopic criteria clearly assist in the distinction of differentiated smooth muscle tumors from amelanotic spindle cell melanomas, schwannomas, and neurofibromas. 9 10

D E C E M B E R , 1968

SUMMARY

Electron microscopic study confirmed that a tumor fulfilling all the light microscopic criteria for the diagnosis of leiomyoma of the ciliary body is composed of smooth muscle. Electron microscopic criteria for the distinction of a leiomyoma of the ciliary body from amelanotic spindle cell melanomas, schwannomas, and neurofibromas are also discussed. ACKNOWLEDGMENT This case was contributed to the Registry of Ophthalmic Pathology by Harry M . Holtz, M.D., and Gabriel Yelin, M.D. REFERENCES 1. Blodi, F. C : Leiomyoma of the ciliary body. Am. J. Ophth. 33:939, 1950. 2. Dunbar, J. C. : Leiomyoma of the ciliary body. Am. J. Ophth. 42:204, 1956. 3. Bonamour, M . M., Bonnet, J. L. and Jambon, Mme.: Leiomyome du corps ciliare; quelques considerations à propos du diagnostic et du traitement des tumeurs bénignes de l'iris et du corps ciliaire. Bull. Soc. Ophtal. Franc. No. 7-8, Aug.-Oct. 482, 1957. 4. Calmettes, L., Deodati, F. and Bec, P. : Leiomyome du corps ciliaire. Bull. Soc. Franc. Ophtal. 74:158, 1961. 5. Fine, B. S. and Zimmerman, L. E. : Müller's cells and the "middle limiting membrane" of the human retina. Invest. Ophth. 1:304, 1962. 6. Jones, R. M., ed.: McClung's Handbook of Microscopical Technique. New York, Hoeber, ed. 3, 1961, p. 244. 7. Bloom, W . and Fawcett, D. W . : A Textbook of Histology. Philadelphia, Saunders, 1962, ed. 8, p. 190. 8. Fisher, E. R. and Vuzevski, V . D . : Cytogenesis of schwannoma (neurilemoma), neurofibroma, dermatofibroma, and dermatofibrosarcoma as revealed by electron microscopy. Am. J. Clin. Path. 4 9 : 141, 1968. 9. Fine, B. S. : Observations on the Axoplasm of Neural Elements in the Human Retina. Proceedings Third European Regional Conference on Electron Microscopy, Prague, Publishing House of the Czechoslovak Academy of Sciences, Series B, p. 318, 1964. 10. Kuwabara, T. : Microtubules in the retina. In Rohen, J. W . (ed.) : The Structure of the Eye: II. Symposium. Stuttgart, Germany. Schattaner-Verlag, 1965, p. 69.