ELASTOGENESIS I N ADENOMATOID TUMOR His t och e m ica 1 and U 1 t yas t ruct ura 1 0 bserva t io ns

MOHAMMED AKHTAR, MD," FRANCISCO REYES, MD,+ AND IRVING YOUNG, M D ~

An adenomatoid tumor from the round ligament of a 50-year-old woman was studied by light and electron microscopy. Ultrastructurally the tumor was re- markably similar t o normal as well as neoplastic mesothelium, thus lending further support t o the concept of a mesothelial origin of adenomatoid tumors. Comparative histochemical and ultrastructural studies revealed presence of acid mucopolysaccharides mainly along the luminal borders of the tumor cells, thus indicating likely production of this material by the tumor cells as opposed to the stromal cells. T h e stroma was rich in elastic fibers and there was evidence of active elastogenesis. This paper represents the first unequivocal demonstration of elastogenesis in a n adenomatoid tumor.

Cancer 37:338-345, 1976.

DENOMATOID TUMORS ARE RELATIVELY UN- A common benign tumors of the genital tract. The histogenesis of these tumors has evoked considerable controversy in the past. Several histogenetic possibilities, including mesonephric, Mullerian, lymphangiomatous and mesothelial origins, have been suggested.6 Recent electron microscopic studies have re- vealed that adenomatoid tumors show a strik- ing resemblance to mesotheliomas, thus s u p porting the mesothelial histogenesis of these t u m o r ~ . ~ . ~ , Q J ~ J 3 This paper describes the histo- chemical and ultrastructural findings in an adenomatoid tumor of the uterine round liga- ment in an attempt to further elucidate the morphogenesis and histogenesis of these tu- mors.

CASE REPORT

A 50-year-old black woman was found at herniorrhaphy to have a tumor of the uterine

From the Department of Pathology, Albert Einstein Medical Center (Northern Div.), Philadelphia, PA.

Present address: M. Akhtar, MD, Assist. Professor of Pathology, University of Texas Health Science Center at Houston, 6400-W Cullen St., Houston, T X 77025.

Attending Pathologist. t Senior Pathology Resident. t Director of Laboratories. Address for reprints: Dr. I. Young, Department of

Pathology, Albert Einstein Medical Center, York & Tabor Rd., Philadelphia, PA 19141.

The authors thank Mr. Chaudhry C. Din for assist- ance in electron microscopy and photography, and Ms. Madeline Lang for typing the manuscript.

Received for publication December 17, 1974.

round ligament. T h e tumor and round ligament were resected. T h e specimen consisted of a round ligament measuring 4 cm in length and 1.2 cm in diameter. Near one end there was a well-circum- scribed 1.5 X 1.5 x 1 cm, moderately firm tumor, which revealed a grayish-white cut surface with several small cystic spaces.

METHODS AND RESULTS

Light Microscopy

The tissue was fixed in 10% acetate buf- fered neutral formalin and embedded in paraf- fin. The tumor consisted of numerous cystic and glandlike spaces with intervening fibrous stroma. T h e cells lining these spaces varied from low cuboidal cells resembling epithelium to markedly flattened cells resembling endo- thelium. In some areas there were solid nests of tumor cells. T h e tumor cells showed vary- ing degrees of cytoplasmic vacuolation (Fig. 1).

Many of the cystic and glandular spaces contained alcian blue positive material dis- posed mostly along the luminal borders of the lining cells (Fig. 2). Treatment with hyalu- ronidase resulted in partial removal of this material. PAS stain was weakly postive, whereas mucicarmin stain was negative. These maneuvers indicate the acid mucopolysac- charide nature of the material with hyalu- ronic acid forming the predominant com- ponent. T h e stroma consisted of dense collagenous tissue in which numerous elastic fibers were also demonstrable by Verhoeffs elastic tissue stain (Fig. 3).

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No. 1 ELASTOGENESIS * Akhtar et nl . 339

FIG. 1 . A represent- ative area of the tu- mor showing several cystic and gland like spaces with interven- ing fibrous strorna (H & E, x160).

Electron Microscopy For electron microscopy Imm-cubes of the

tumor were fixed in 2% gluteraldehyde (ph 7.3) washed in cacodylate buffer, post-fixed in osmium tetroxide, and embedded in Epon 812. Ultra-thin sections were stained with uranyl acetate and lead citrate. One-micron sections were stained with toluidine blue for orientation.

The tumor was comprised of varying sized

FIG. 2. A cystic space containing acid rnucopoly- saccharides disposed as a layer of alcian blue positive substance along the luminal borders of the cells and as irregular deposits in the lumen. (Alcian blue stain, (X400).

cystic and gland-like spaces which were lined by low cuboidal to markedly flattened tumor cells and were separated from one another by variable amounts of stroma. The tumor cells were rich in cytoplasmic organelles which included irregularly arranged bundles of fine filaments, moderate amounts of rough sur- faced endoplasmic reticulum, several mito- chondria, and occasional clusters of glycogen particles. Adjacent tumor cells had tortuous cell borders and their plasma membranes were closely approximated except for several ran- domly distributed areas where they were sep- arated by intercellular spaces of various sizes and shapes. Several well-developed desmo- somes and tight junctional complexes were also seen (Fig. 4). The tumor cells were sep- arated from the surrounding stroma by well- developed basal laminae (Fig. 7). The luminal borders of the cells frequently showed numer- ous microvilli (Fig. 4). Some of the cysts contained a layer of finely granular material covering the luminal surfaces of the lining cells (Figs. 5 and 6). Irregular aggregates of similar material were also seen lying free in the lumina of these spaces. Occasionally this material was admixed with aggregates of markedly dense, fibrillar material (Fig. 6). The stroma consisted of fibroblasts surrounded by bundles of collagen fibers. Several areas in the stroma also contained irregularly shaped struc-

340 CANCER January 1976 VOl. 37

tures, each consisting of a peripheral fibrillar zone and a central amorphous zone. These structures were closely associated with collagen fibers and fibroblasts and their transition to fully developed elastic fibers was readily ap- parent (Figs. 7 and 8).

DISCUSSION

The ultrastructure of this tumor is essen- tially similar to that described in previously published electron microscopic studies of ade- nomatoid tumor~.4~*,9,11J3 T h e tumor in our case as well as in the previous studies shows a striking resemblance to mesotheliomas aris- ing in extragenital sites such as pleura and peritoneum.4~7~9J4 There is also a close re- semblance to normal and stimulated mesothe- lium.ZJ6 In view of these facts, the concept of a mesothelial histogenesis of adenomatoid tu- mors appears most reasonable.

The presence of acid mucopolysaccharides in adenomatoid tumors is well recognized.3312 Although most reports localized acid muco- polysaccharides to the cystic spaces, there has been some speculation as to the possibility of derivation of this substance from stromal c e k 4 In the present study a comparison of light microscopic and ultrastructural findings clearly indicated that a layer of finely granular material seen ultrastructurally along the lu-

FIG. 3. An area of tumor showing sev- eral elastic fibers in the stroma. (Verhoeff’s elastic tissue stain, (X160).

minal borders of the tumor cells (Figs. 5, 6) corresponded to the alcian blue positive ma- terial seen by light microscopy (Fig. 2). Ultra- structural localization of mucopolysaccharides has not been accomplished in previous elec- tron microscopic studies on adenomatoid tu- mors. A similar localization of acid mucopoly- saccharides, however, has recently been demonstrated in a pleural mesothelioma by ultrastructural histochemistry.14 These find- ings would indicate that in these tumors mucopolysaccharides are produced principally by the mesothelial rather than the stromal cells.

The nature of the dense fibrillar material (Fig. 6) seen intermixed with the finely gran- ular substance in some of the cysts, is not clear. T h e constant close association of the dense fibrillar material with the fine granular material suggests that the former is produced as a result of alteration in the acid mucopoly- saccharides.

The presence of elastic fibers in the stroma of the adenomatoid tumors has not been pre- viously recognized. In our case numerous elastic fibers were demonstrated by elastic tis- sue stain and also at an ultrastructural level. T h e possibility that this merely represented preexisting elastic fibers from the round liga- ment, incorporated into the tumor, was con- sidered unlikely since all stages of morpho-

No. 1 ELASTOGENESIS Akhtar et al.

FIG. 4. Another area of the tumor showing cystic spaces lined by tumor cells with well- developed microvilli. The cells contain bundles of cytoplasmic filaments, profiles of rough endoplasmic reticulum and several mitochondria. Cell borders are tortuous and show well- developed desmosomes (arrows) (~25000).

34 I

342 CANCER January 1976 VOl. 37

FIG. 5. Electron mi- crograph of an area of the tumor showing cystic spaces and sev- eral smaller intercel- lular spaces. One of the cysts shows finely granular material dis- posed along the lumi- nal borders of the cells and also as irregular aggregates in the lu. men ( ~ 7 1 0 0 ) .

FIG. 6. Electron mi- crograph showing por- tion of the wall of a cystic space lined by flattened tumor cells with a few microvilli. The luminal border is covered by a layer of finely granular mate- rial. The lumen con- tains similar finely granular material in- termixed with aggre- gates of markedly dense fibrillar material (x 12230).

No. 1 ELASTOGENESIS * Akhtar et al.

FIG. 7. An area in the stroma showing a fibroblast with prominent rough surfaced endoplasmic reticulum. The cell is surrounded by collagen fibers. Also present are aggregates of finely fibrillar material which show early development of amorphous zones (large arrows). These aggregates represent very early elastogenesis. Also noted is a portion of a tumor cell segregated from the stroma by basal lamina (small arrow) (x2oooO).

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344 CANCER January 1976

FIG. 8. Another area in the stroma showing a well developed elastic fiber (xSoo00).

Vol. 31

No. 1 ELASTOGENESIS - Akhtar et al. 345 genesis of elastic fiberslJ910 indicating active tures morphologically similar to the develop- elastogenesis were readily demonstrable. ing elastic fibers noted by us were encountered,

In some of the previous electron micro- but their relationship to elastic fibers was not scopic studies of adenomatoid tumors, struc- recognizecL4~s

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