Fetus amorphus or placental teratoma?

TERATOLOGY 4O:l-10 (1989)

Fetus Amorphus or Placental Teratoma? TRENT D. STEPHENS, RICHARD SPALL, ALEXANDER G. URFER, AND ROGER MARTIN Department of Biological Sciences, Idaho State University. Pocatello. Idaho 83209

ABSTRACT A differential diagnosis between fetus amorphus and placental teratoma based on the presence of a n umbilical cord and/or skeletal organization in the fetus amorphus has been proposed (Fox and ButlerManual: Journal of Pathology 88:137-140, 1964). We report a description of one new case of fetus amorphus, along with the results of a critical reexamination of 96 cases from the literature. Our findings fail to support the proposed criteria for distinguishing fetus amorphus from placental teratomas. We find that the presence or absence of a n umbilical cord does not relate a t all to the developmental state of the specimen. The extent of skeletal development may be a more valid criterion; however, the internal organization in the fetus amorphus forms an anatomical continuum with that of the placental teratoma, making a differential diagnosis meaningless. Additional research is necessary to solve this dilemma. The receipt of a bovine amorphus acormus acardia in 1983 caused us to consider a number of questions concerning this rare anomaly. One of us (Stephens, ’84) had previously investigated a number of human acardiac specimens and noted a striking contrast between those specimens and the present one. The bovine specimen exhibited no internal organs, which are common in many human cases of amorphus acardia, and resembled a teratoma more than a typical acardiac. This finding stimulated us to conduct a literature search in an attempt to determine if other reported cases of amorphus acardia exhibited a similar lack of internal organization and we found a surprising number of reported cases of amorphus acardia similar to our specimen. These findings called into question whether some specimens classified as amorphus acardia (and some other types of acardia) could actually be teratomas. The purpose of the present paper is to evaluate the hypothesis that there are a t least two subgroups of amorphus acardia: 1) the more standard type, with recognizable internal organs and skeletal structure, and 2) teratoma-like specimens with no recognizable internal organs or skeletal structure. The criteria for differential diagnosis

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1989 ALAN R. LISS. INC.

of Fox and Butler-Manual (’64)and Calame and van der Harton (’85)are also addressed. MATERIALS AND METHODS

The specimen

The specimen was delivered February 20, 1981, a t the range of Reed Hansen, Blackfoot, Idaho, to a n Angus cow bred to a Hereford bull. Its cotwin was a n apparently normal heifer calf. The calf and specimen were delivered a t night while unattended. When they were first observed in the morning, the placenta had already been consumed by the mother. The farmer assumed that there was only a single placenta because, “The mother usually doesn’t clean up [consume] a dead one [i.e., the placenta of a dead calfl.” Literature search

A literature search was conducted by three methods: 1) Files of published acardia papers (T.D. Stephens’ files).

Received March 1 . 1988: accepted December 2. 1988

2

T.D. STEPHENS ET AL

Fig. 1. External characteristics of specimen. Specimen showing tongue-like structures, lingual papillae, and tooth-like structures.

2) Medline computer search for acardius, amorphus, and teratoma. 3) Citations in papers obtained by methods 1 and 2.

We are aware that this search is not complete. For example, Taruffi (1885) lists 98 cases that we did not include in our review and Strong and Corney ('67) listed 19 references t ha t we did not include.

RESULTS

Description of the specimen

The specimen consisted of a n oval mass measuring 12 cm x 12 cm x 18 cm and was covered with white hair (Fig. 1). One end of the mass exhibited several tongue-like structures, complete with lingual papillae, and a number of disorganized tooth-like

FETUS AMORPHUS OR PLACENTAL TERATOMA?

3

Fig. 2. Radiographic analysis of specimen. Specimen shows disorganized mass of tooth-like structures a t the “oral” end but no other mineralized tissue anywhere else in the specimen.

structures. The opposite end exhibited a small patch of black hair. This particular variety of cattle normally has a white face and black body, so it was assumed that the specimen consisted almost entirely of a “head” and was accordingly designated as a n acormus (without a body). A torn, cordlike mass of tissue was found near the pole opposite the “oral” end of the specimen. Radiographic analysis revealed a disorganized mass of tooth-like structures a t the

“oral” end of the mass (Fig. 2), but no other mineralized tissue was found anywhere in the specimen. No organized internal structures or recognizable organs were found upon dissection. Tissue samples were taken from a number of sites in the specimen and were prepared for light microscopy. Histologic examination revealed the presence of a variety of epithelial tissues including morphologic types typically associated with skin;

4

T.D. STEPHENS ET AL

tongue; gut with goblet cells, villi, and crypts of Lieberkuhn; blood vessels; ducts; and glands (both salivary-like glands and prostate-like glands). Connective tissues, including general connective tissue, cartilage, and adipose tissue; hematopoietic tissue; and lymphoid nodules were found. Also, both organized and disorganized muscle tissue and nerves were present.

Literature search Our literature search revealed a total of 101 reports of amorphus acardia (fetus amorphus) or acormus acardia. Information contained in 60 of those papers and data from a n additional 33 reports previously summarized by Heijl(’10) and Simonds and Gowen (’25),for a total of 93 reports, were included in the present review. The data from the remaining eight papers were not available. Eight of the 93 papers reviewed presented insufficient data for analysis, three papers were actually reports of conjoined twins, and one was a report of a fetus in fetu. Data from the remaining 81 reports, in which 96 cases of amorphus or acormus acardia were reported (plus the present case), are listed in Table 1. Eighty-two of the reported cases were from humans, 12 cases were from cattle, and two cases were from sheep. Twenty-eight of the cases exhibited the “classic” characteristics of amorphus acardia, i.e., a fairly well-developed vertebral column plus some other skeletal structures (such a s skull, limbs, or ribs); 15 additional cases exhibited some vertebrae (one to eight vertebrae); eight exhibited only skull bones and/or teeth (including the present case); nine exhibited only long bones, resembling those of the limbs; 29 exhibited only disorganized bone fragments; and nine contained no bone at all. Thirty-six specimens exhibited a n umbilical cord, nine did not, and data regarding this feature were not available for the remaining 52 specimens. In a large number of the reported cases, the placenta was not extensively described. Often the placenta was discarded before it could be evaluated. When the placenta was described, the description often only included the measurements and weight of the placenta. The fetal membranes were seldom described, aside from the occasional statement that they were monoamnionic and monochorionic, for example.

Several cases from the literature are worth special mention. There were a number of almost identical small ovoid masses (ranging in greatest length from 6 cm to 10.5 cm) with little or no internal organization (Webster, ‘06; Slemons, ’17; Schultze, ’33; Ross, ’51, Ketchum and Motyloff, ‘57; Napolitani and Schrieber, ’60; and Praetorius, ’63). In five cases it was stated or shown that the mass was attached to the edge of the placenta by a n umbilical cord ranging in length from 4 to 5 cm (Schultze, ’33; Ross, ’51; Ketchum and Motyloff, ’57; Napolitani and Schreiber, ’60; and Praetorius, ’63). At least three of those five cords (Schultze, ’33; Ross, ’51; and Ketchum and Motyloff, ’57) consisted of a deltoid extension of the amnion covering the placental surface and contained umbilical vessels (usually one artery and one vein); whether those cords contained Wharton’s jelly was never stated. In the two cases where the authors stated that there was no umbilical cord (Webster, ’06, “No cord is present”’ and Slemons, ’17, “. . . a kidney-shaped mass . . . attached by a pedicle . . .”), one (Webster, ’06)was attached to the edge of the placenta by 8 cm-long “membranes” containing a n umbilical artery and vein, and the other (Slemons, ’17) was attached to the edge of the placenta by a 12 cm-long “pedicle” covered for the first 11 cm by amnion and containing a n artery and vein. Calame and van der Harten (’85) described a n amorphous mass (10 x 7.5 x 5 cm) attached to the side of the placenta, “without signs of a (rudimentary) umbilical cord,” par1 of which w a s located Letweell the amnion and chorion of the placental chorionic plate. But upon microscopic examination they found, . . . a n umbilical cord with Wharton’s jelly and two vessels . . .” Because of this microscopic umbilical cord, and based on the criteria of Fox and ButlerManual (’64), Calame and van der Harten (’85) concluded that, “. . . our case is a n example of fetus acardius.” On the other hand, Smith and Pounder (‘82) concluded, based on the criteria of Fox and ButlerManual (’64), that their specimen was a placental teratoma because it had ‘‘ . . . no umbilical cord . . .” but “. . . received its blood supply from a few vessels . . .” and the “tumor” was attached to the edge of the placenta where, “. . . the squamous epithelium became thinner and merged with the amnion.” Figure 2 from Smith and Pounder “

FETUS AMORPHUS OR PLACENTAL TERATOMA?

(’82) looks almost identical with Figure 7

from Calame and van der Harten (’85) except for the width of the placental attachment. The paper by Corner (’01) is also worth special mention in relation to tumors, fetuses, and umbilical cords. He described a fetus amorphus attached to the placenta by a “small” umbilical cord, while, “Attached to the head [of the amorphic fetus] is a large bilobed tumor . . .” consisting partly of “placental” tissue? An “umbilical” cord, larger than that of the fetus amorphus, was attached to the “tumor.” COMMENT

We have been able to evaluate 96 cases of amorphus and acormus acardia in the literature. Furthermore, Calame and van der Harten (’85) have cited eight cases of placental or umbilical cord teratomas, and Joseph and Vogt (’73) have cited one additional case, for a total of nine cases. Calame and van der Harten (’85) stated that differential diagnosis between a placental teratoma and a fetus amorphus should be based on the presence of at least a rudimentary cord and the presence or a t least indication of skeletal development in the craniocaudal direction. They cite Fox and Butler-Manual (’64) as authority for their statement. Concerning a differential diagnosis, Fox and Butler-Manual (’64) stated “. . . it is generally agreed t hat the amorphus mass is a blighted foetus. This being so it follows that such a foetus will have a separate umbilical cord, . . . The cord may be poorly developed or even rudimentary. . . . Therefore, the first point of differentiation between a foetus amorphus and a placental teratoma is the presence or absence of an umbilical cord.” They added, “The pattern of skeletal development [in the fetus amorphus] is notably consistent, in that the vertebral column is partially or wholly present in a n easily recognizable form . . . This degree of skeletal development does not occur in a teratoma. . . .” Therefore, according to Fox and ButlerManual (’64) and Calame and van der Harten (’85), the criteria for differential diagnosis between a placental teratoma and a fetus amorphus is the presence of 1) an umbilical cord and 2) a vertebral column or craniocaudal skeletal organization. These criteria seem to be extremely fragile. First,

5

the criterion of a n umbilical cord is based on the assumption by Fox and Butler-Manual (’64) that, “. . . a foetus will have a separate umbilical cord . . .” and is not supported by data. The second criterion, th a t of skeletal organization, which Fox and Butler-Manual (’64) called “. . . notably consistent . . .” was also not supported by the data in their paper. Both of these “criteria” for differential diagnosis must therefore be viewed only as suggestions and need to be further evaluated. Information on the presence or absence of a n umbilical cord was only available for 45 of the cases that we reviewed. Thirty-six of these had an umbilical cord, and nine did not (the specimens were “attached directly to the placenta”). Of the 36 cases with cords, 19 were associated with specimens having vertebrae, seven with specimens having skull or limb fragments only, and ten with specimens exhibiting no bone or only bone fragments. Additionally, it is commonly believed that the length of the umbilical cord is influenced or even determined by the motion of the fetus. However, one of the ten specimens with a n umbilical cord evaluated in this review was only a very small oval mass with a 60 cm-long umbilical cord (Ruge, ’37). It is difficult for us to believe that in this case the length of the umbilical cord was determined or even influenced by the “motion” of a small ovoid mass with very little organization. Furthermore, there are numerous cases of cyllosomus and pleurosomus in which a t least three limbs form with normal muscular structure (cf. Pagon e t al., ’79), suggesting relatively normal motion, yet in every case there is little or no umbilical cord. A related paradigm states that internal teratomas have no umbilical cord, and therefore, any delivered mass with an umbilical cord cannot be a teratoma. However, Gale and Willis (’44) described a retroperitoneal teratoma attached to the host by only a 1 cm-diameter pedicle; and Kimmel et al. (’50) noted that two of five “fetuses” found inside a cerebral teratoma “possessed umbilical cords.” Once more, the data do not support the commonly held beliefs. Of the nine cases with no umbilical cord, one was associated with a specimen having vertebrae, one with a specimen having only limb-like bones, and seven were associated with specimens containing no bone or only bone fragments. It seems quite clear from

6

T.D. STEPHENS ET AL.

TABLE 1 . Summary of data' Author Present case Aga and Gupta Alderman Ali Ballantyne Beerens Benedetti Benirschke Benirschke Benirschke Benirschke Benirschke Bieber et al. Bjoro Bland Bland-Sutton Boldt Boulware Brand and Krol Brodsky Calame and van der Harten Calori Charlton Corner Cornil and Cousit Crede Dugal Dunn e t al. Ehrmann Fielding and Kvitka Freudenberg Gamboa Garrigues Gluge and Dudekem Graetz Gruenbaum Guenoit Gurlt Gurlt Heberer Heijl Heller Hermann and Bluett Hirschbruch Holterman Hunziker Kappelman Keen

Date of source ('64) ('73) ('62)

H,S&G ('26)

S&G ('59) ('59) ('59) ('59) ('59) ('81) ('57)

H,S&G S&G H,S&G ('30) ('42) ('39) ('85)

H,S&G ('01) ('01)

H,S&G H,S&G S&G ('67)

S&G ('57)

H,S&G ('64)

H,S&G S&G H,S&G S&G ('06)

S&G S&G ('55)

H H,SLC. H,S&G H ('27) ('07) ('44) ('47)

Host cow Human Human Human Human Human Human Human Human Human Human Human Human Human Human cow Human Human Human Human Human Human Human Human Human Human Human cow Human Human Human Human Human Human Human Human Human cow cow Human Human Human Human Human Human Human Human Human

these data that there is no correlation between the presence or absence of an umbilical cord and the internal skeletal organization of the amorphus mass, and therefore the presence or absence of a cord is not a clear criterion of classification. The second proposed criterion is that skeletal organization is present in the fetus amorphus and is lacking in the teratoma. Our examination of the data from 97 reported cases reveals that a vertebral column is not ". . . notably consistent . . . in an easily recognizable form. . . ." We found only 28 of

A

B

+ +

C

D

E

F

4

+

+ + +

?

?

?

+

+

?

+

-

+ + +

+

-

+

+ + +

?

-

G

t

? ? ?

+

+

+

+ + +

+

?

+

+ +

+

+

?

? ? ?

+

+

?

+?

+ +

?

? ? ?

+ + +

+

+

+ + +

+

?

? ?

-

+

?

? ?

+ +

+ + +

+ + +

i

?

+

+ + +

+ + + +

+ (Continued)

the 97 reported specimens (29%) with a fairly well developed vertebral column and only 42 specimens (43%) with any vertebrae. As far as craniocaudal skeletal organization is concerned, 39 of the 97 specimens reported (40%) had either no bone at all or only disorganized bone fragments. Our findings suggest that neither the criterion of vertebral column development nor craniocaudal skeletal organization is a good functional criterion to distinguish between placental teratoma and fetus amorphus, since fewer than one-half of the spec-

7

FETUS AMORPHUS OR PLACENTAL TERATOMA?

Author Ketchum and Motvloff Kleinwachter Kroner and Schuchardt LeVine and Wolf Marruz Morlunghi Mueller Napolitani and Schreiber Neitzschman e t al. Neugebauer Nitschmann Noeggerath Panum Phelan and Abbott Pok Praetorius Rashad and Kerr Richart and Benirshcke Rise1 Ross Ruge Schiller Schlipp Schmid Schmincke Schmincke Schmincke Schmincke Schmincke Schmincke Schmincke Schmincke Schmincke Schmincke Schultze Schwalbe Simonds and Gowen Slemons Smith and Pounder Stewart Van Tongeren Vallisneri Van Allen e t al. Vartfall Vrolik Webster Webster Will ~

Table 1ASummnry of Data' (Continued) Date of source Host A B C + + ('57) Human Human ? H,S&G Human ? + H,S&G + + Human ('40) + Human ('36) + Human ('54) Human ? + H,S&G + Human ('60) ? + Human ('73) ? + Human H,S&G + Human 1'27) Human ? S&G + ? Human H 9 Human S&G + Human ('19) + Human ('63) Human ? ('66) + + Human ('63) + + Human ('13) + + Human ('51) + Human ('37) ? + Human H,S&G Human ('54) + Human ('36) cow S&G cow S&G cow S&G cow S&G cow S&G ? cow ? S&G cow ? S&G ? cow S&G ? + Sheep S&G Sheep ? S&G Human ('33) Human ? + H,S&G + + Human ('25) +Human ('171 Human ('82) + + Human ('131 + + Human ('32) Human S&G ? + + Human ('83) Human H ? > + Human H Human ('06) + Human ? + S&G + + Human ('47)

~~~~

D

E

F

G

i

+

+ I

+

+

-t

+

+ + t

+

+ +

+ +

+ + +

+ + +

+ + + + + + t

~

'A = umbilical cord or Wharton's Jelly, -, absent, + , present, 7, unknown, B = vertebral column (nearly complete + other structures such as skull, ribs or limbs), C = vertebrae (incomplete column + part of skull or pelvis), D = skull. skull bones, or teeth, E = " l i m b bones, F = bone fragments, G = none bone. B-G + , indicates the type or amount of bone formation occurring in the specimen Source H = Heigl ('lo), S&G = Simonds and Gowen ('25)

imens exhibited any vertebral development and nearly one-half exhibited no skeletal organization. Alternatively, it might be concluded that approximately one-half of the reported cases of amorphus acardia or acormus acardia are actually placental teratomas. Furthermore, the presence of an axial skeleton does not rule out the possibility that the specimen is neoplastic in nature; e.g., elements of axial skeletons have

been found in ovarian teratomas (Riopelle, '40), and axial skeletons and limbs have been found in cases of fetus in fetu (Kimmel et al., '50; Boyce et al., '72). It might be concluded that development and histogenesis are poor criteria for obtaining a differential diagnosis for placental "fetiform" masses. Fox and Butler-Manual ('64) suggested that five reported cases of fetus amorphus

8

T.D. STEPHENS ET AL

should be reclassified as teratomata. Those included four cases listed in our Table 1 (we did not see any data on the one other case): Ballantyne, Brodsky, Ruge, and Slemons. We agree with that assessment; each of those cases contained only bone fragments. However, a n additional 35 specimens also fit into that category (using the criterion of no skeletal organization). Furthermore, when we examined the four reported cases just listed, three of the four specimens had umbilical cords (Brodsky, Ruge, and Slemons). Information regarding a n umbilical cord was unavailable for the fourth (Ballantyne). Brodsky (’39)specifically stated that his specimen contained the, . . remnant of the ‘umbilical’ cord,” and the specimen described by Ruge (’37) had a 60 cm long umbilical cord. It is surprising that Fox and Butler-Manual (’64) would establish rigid criteria for discriminating between placental teratomas and fetus amorphi and report five cases in the literature as being misdiagnosed, when at least three of the five did not fit one of their two criteria (that a placental teratoma does not have a n umbilical cord). We find, after reviewing over 100 cases of fetus amorphus and placental teratoma, that a differential diagnosis is very difficult, if not impossible, to establish at the present time. The criteria of a n umbilical cord and skeletal organization proposed by Fox and Butler-Manual (’64) are not supported by data. Our analysis of the data indicates that the presence or absence of a n umbilical cord is not a valid criterion and should not be employed. The concepl of skelelal urgailization perhaps has more merit. It may be that amorphus masses with little or no internal skeletal organization are placental teratomas rather than fetus amorphi. If so, a t least 40% of the reported cases of fetus amorphus are actually placental teratomas. While it could be argued that lack of skeletal organization might constitute a priori evidence of a neoplastic lesion, the reverse is certainly not true since, as was documented above, extraplacental teratomas and fetus in fetu with axial skeletons and limbs have been found. We urge caution in making a diagnosis of placental teratoma in specimens without skeletal organization. First, based on morphological findings only, there is no way a t the present time to confirm such a diagnosis. Second, there is a continuum of amor‘I.

phus specimens that exhibit various degrees of skeletal-element formation. They range from specimens that contain a nearly complete vertebral column to ones with no bone development. Therefore, establishment of a differential diagnosis between amorphi and teratomas on this basis is, a t best, arbitrary. Third, there are well-known cases of extraplacental teratomas (or fetus in fetu) where considerable internal skeletal organization has occurred. Therefore, the desire to categorize a n amorphus specimen must be tempered by the realization that the criteria upon which a differential diagnosis is made are ambiguous and weak. It seems appropriate that additional attempts be made to identify some other criteria for differential diagnosis. Stephens (’84)has proposed t h a t there are multiple etiologies for fetus amorphus. It is also possible that there are multiple etiologies for teratomas. At present, teratomas are primarily viewed as arising from pluripotent embryonal germ (or “stem”) cells. The experimental work of Stevens (’62,’67a, b,’68,’70), Pierce (’67), and others supports this view. However, the postembryonic persistence of germ cells a s “stem-cell rests” as well a s their origins and patterns of migration remain incompletely defined. There is evidence that failure of these cells to reach the genital ridge impedes their differentiation (Ozdenzenki, ’69). What remains to be shown is whether misguided germ cells have a propensity to undergo neoplastic transformation, and, if they do, how such phenotypic alterations can be explained by current (“genetic”, theories of oncogenesis. These proposals can only be tested when we have developed reliable diagnostic criteria and/or suitable animal models. The term fetus amorphus has historically been used to describe any defective birth that lacks major external anatomic features such a s a head and limbs. However, no distinction has been made concerning internal organization. Some cases of fetus amorphus exhibit a relatively complete vertebral column and several well-formed internal organs, while others lack any organized skeleton or organs. This classification problem is compounded when attempts are made to assign etiologies to these types of defects. For example, Van Allen e t al. (’83) have proposed the term “twin reversed arterial perfusion (TRAP) sequence” as a replacement for the

FETUS AMORPHUS OR PLACENTAL TERATOMA?

term acardia. The concept of radically different etiologies for fetus amorphus and placental teratoma is appealing and makes a differential diagnosis seem imperative. However, since fetus amorphus and placental teratoma form a n anatomical continuum with no clear point of separation, a differential diagnosis becomes arbitrary and, therefore, rather meaningless. If the term fetus amorphus was only descriptive and referred to any amorphous mass, no matter what the origin (as was likely the original intent), then a differential diagnosis would not be necessary. However, modern biomedical practice is, justifiably, not satisfied with only descriptive terms, which provide no suggestion of etiology. Therefore, it would appear that the only answer to this dilemma is that more research be conducted to establish clear etiologies for placental teratomas and the several types of fetus amorphus, and to identify more specifically certain morphologies with certain etiologies. In conclusion, the determination of whether a given specimen is a fetus amorphus or a placental teratoma is a difficult one to make, largely because these types of defects lie upon two portions of a continuum, with no point of clear separation between them. I t appears to us that even though classification of a n amorphous mass with little or no internal organization as either a fetus amorphus (acardia) or a s a placental teratoma is important from a n etiological perspective, such classification is a t present arbitrary and will, itself, depend on a more clearly established set of etiologies. ACKNOWLEDGMENTS

We wish to thank Mr. Reed Hansen for providing the specimen. We are grateful to Dr. E.E. Fisher and Mr. Dennis Merrell, Bannock Regional Medical Center, Pocatello, Idaho, for their help in histology and radiology. We also wish to thank Dr. H. Wayne Schou for his help in translation of the Scandinavian papers. This project was funded by local Department of Biological Sciences funds. LITERATURE CITED Aga, V., and D.N. Gupta (1964) Amorphus parasitic twin-a case report. Indian J. Pathol Microbiol., 7: 255-258. Alderman, B. (1973) Foetus acardius amorphus. Postgrad. Med. J., 49:102-105.

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Ali, R. (1962) Zeldzame misvormingen big monozygote tweelinger. Ned. Tijdschr. Geneesk., 206t184-187. Beerens, J . (1926) Un cas de teratologie. Bruxelles Med., 7:60,61. Benirschke, K. (1959) Nuclear sex of holoacardii amorphi. Obstet. Gynecol., 24:72-78. Bieber, F.R., W.E. Nance, C.C. Morton, J.A. Brown, and F.D. Redwine (1981). Genetic studies of an acardiac monster: Evidence of polar body twinning in man. Science, 223:775-777. Bjoro, K. (1957) Parasitaere tvillinger et filfelle au acardius amorphus. Tdsskr. Norske Laegeforen, 77: 344-346. Boulware, T.M. (1930) An unusual acardiacus. Am. J . Obstet. Gynecol., 20:708-709. Boyce, M.J., J.W. Lockyer, and C.B.S. Wood. (19723 Foetus in foetu: Serologic assessment of monozygolic origin by automated analysis. J. Clin. Pathol., 25: 793-799. Brand, J.E., and B. Krol(1942)Acardius pseudacormus. Beitr. Pathol. Anat., 206:113-128. Brodsky, I. (1939) Foetus amorphus. Med. J. Aust., 2:539-542. Calame, J.J., and J.J. van der Harten (1985) Placental teratoma or Acardius amorphus with amniotic band syndrome. Eur. J. Obstet. Gynecol. Reprod. Biol., 20:265-273. Charlton, G.A. (1901) Description of a foetus amorphus. J. Anat., 36:78-80. Corner, E.M. (1901) Acardiac monster caused by a foetal adhesion to a placenta succenturiata. J. Anat., 36:81-92. Dunn, H.O., D.H. Lein, and R.M. Kenney (1967) The cytological sex of a bovine anidian (amorphus) twin monster. Cytogenetics, 6t412-419. Fielding, W.L., and L. Kvitka (1957) Intrapartum uterine rupture with an acardius amorphus second twin. Obstet. Gynecol., 20:313-315. Fox, H., and R. Butler-Manual (1964) A teratoma of the placenta. J. Pathol., 88:137-140. Gale, C.W., and R.A. Willis (1944) A retroperitoneal digit-containing teratoma. J Pathol, 56:403-409. Gamboa, G.R. (1964) Holoacardius amorphus. Rev. Colombia ObsteL. Gynecol., 25:151-157. Guenoit, P. (1906) Presentation d'un monstre anidien. Bull. SOC. Obstet., 9:183. Heberer, H. i1955) Eine seltene Form von Acardiacus amorphus. Reitr. Geburtsh. Gynak., I f t385-400. Heijl, C.F. (1910)Ett fall af acardius amorphus. Hygiea, 10:747. Holterman, A. (1927) Holocardius amorphus. Med. Klin. (Barc.). 23:460. Hunziker, H. (1907) Beitrag zur Lehre vom Acardium amorphus. Beitr. Geburtsh. Gynak., 22:385. Joseph, T.J., and P.J. Vogt (1973) Placental terataomas. Obstet. Gynecol., 41.574-578. Kappelman, M.D. (1944) Acardius amorphus. Am. J. Obstet. Gynecol., 47:412-416. Keen, J.A. i1947) Foetus holo-acardius amorphus. Clin. Proc.. fi:'LSB-BSS. ~.~ - ~-~ - - Ketchum, J . , and L. Motyloff (1957) Chorioangiopagus parasiticus (Schwalbe), Report of a case of acardius acephalus and of a case of fetus amorphus. Am. J . Obstet. Gynecol., 73:1349-1354. Kimmel. D.L., E.K. Moyer, A.R. Peale, L.W. Winborne, and J.E. Gotwals (1950).A cerebral tumor containing five human fetuses. Anat. Rec., 206t141-165. LeVine, I., and I.J. Wolf (19401 Diffcult labor due to amorphous monster. Am. J. Obstet. Gynecol., 40: 327-329. ~

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T.D. STEPHENS ET AL

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