Prune Belly Syndrome : Report of Twelve Autopsy Cases and Possible Pathogenesis

Cong. Anorn., 25: 1-15, 1985 Original

Kenji KAWAMOTO, Takayoshi IKEDA, Takeshi MATSUO, Hiroshi MAEDA, Naomasa OKAMOTO*, Yukio SATOW*, Naotaka AKI- MOTO* and Juing-Yi LEE* 1st Department of Pathology, Nagasaki University School of Medicine, 12-4 Sakamoto-rnachi, Nagasaki 852, Japan and *Department of Geneticopathology, Research Institute for Nuclear Medicine and Biology, Hiroshima University, 1-2- 3 Kasumi, Minarni-ku, Hiroshima 734, Japan

ABSTRACT Twelve autopsy cases (9 males, 3 females) of the prune belly syndrome are presented. Principal anomalies of this syndrome are a prune-like abdominal feature and a giant bladder. Urethral atresia was observed in most but two cases. Imperforate anus and rectovesical fistula were observed in 8 and 7 cases res- pectively. Associated anomalies were those which may or may not be embryologically related to the principal anomalies. As regards the pathogenesis, the authors propose that a primary defect may occur during any developmental stage of the somitic mesoderm, genital tubercle and urethra. In conclusion, the prune belly syndrome may be of spectrum anomalies depending on the stage specificity mainly in the abdominal wall and genito-urinary organs. Key words: prune belly syndrome, absence of abdominal muscles, pathogenesis

The prune-belly syndrome is a rare congenital malformation characterized by the typical triad, comprising abdominal muscle deficiency, urinary tract abnormalities and cryptorchidism. Ths condition was first reported by Frohlich in 1839 and Parker (1895) proposed the above triad. Further, Osler first coined the term "prune-belly syndrome" for this condition in 1901, based on the charac- teristic wrinkled. appearance of the abdomen. The prune-belly syndrome is also known as congenital absence of abdominal muscles (Housden, 1934), Eagle-Barrett syndrome (Eagle and Barrett, 1950), congenital deficiency of the abdominal musculature and obstructive uropathy (McGovern and Mar- shall, 1959), triad syndrome (Nunn and Stephens, 1961) and abdominal musculature deficiency syndrome (Welch, 1979). Various associated anomalies such as gastrointestinal, orthopedic, cardiovascular and thoracic anomalies have been reported. It occurs predominantly in males, but rarely in females (Welch, 1979; Hirao et al., 1974; Sakuma et al., 1980). 2 K. Kawamoto et al.

On the other hand, the pathogenesis of the prune-belly syndrome has been a long-standing, unset- tled controversy to date. The purpose of this paper is to report twelve autopsy cases of the prune-belly syndrome that were experienced during 31 years between 1952 and 1982 and to discuss the possible pathogenesis of this syndrome.

CASE REPORTS

The cases are listed in Table 1. A. Clinical and biometrical data (Table 1) Among 12 cases presented, nine were male and three were female. Six cases were still-born, four were of neonatal death and two were unknown. Seven cases were born after more than 9 months of pregnancy while 5 cases were premature. The youngest case was 4 month old in fetal age (Case 1, Fig. 2A). The body weight was heavier or normal in most cases compared with normal fetuses and newborns, but Cases 9 and 11 showed a relatively low weight. The abdominal circumference was markedly larger than that in normal fetuses of corresponding gestational age and the size of the urinary bladder was also giant in most of the cases. The mean maternal age of six cases was 25.8 year old. In Case 12, an ultrasound scan at the 25th week revealed oligohydramnios and a cystic lesion in the fetal abdomen. B. Autopsy findings 1. Major anomalies (Table 2) Major anomalies were observed in three organ systems as shown in Table 2. a) kbdomen. In all cases, the abdominal wall was markedly distended and was typically wrinkled, resembling to a prune (Fig. 2). Histologically, the musculature of anterior abdominal wall was absent in two of eight cases examined, in which dense collagenous bundles were formed in the area corresponding to the muscular bundle (Fig. 4C, D). In six of eight cases, the anterior abdominal muscles showed moderate to severe hypoplasia, in which their muscle fibers were scattered and surrounded by sparse collagen fibers (Fig. 4A, B). No muscular degeneration nor necrosis was noted. b) Urinary tract anomalies. The bladder was extremely distended and showed thickening of the walls with muscular hyperplasia except for Case 4. Histological structure of the bladder wall showed an increase of fibrous connective tissue especially in the submucosal and muscle layers, sur- rounding individual muscle fibers (Fig. SA), although in only Case 4 the wall of the bladder was rather thinner (Fig. 5B) and showed an increase of fibrous tissue and a decrease of muscular cells. Among nine cases of the kidney examined histologically six cases exhibited the characteristics of renal dysplasia corresponding to the type 2 of Potter’s classification of cystic kidney. These kidneys were always smaller than normal in size. The microscopic features of renal dysplasia were characterized by cystic dilatation of tubules surrounded by immature mesenchymal tissue, islands of cartilage and diminished glomeruli (Fig. 6A, B, C). The kidney in Case 4 showed subcapsular cysts corresponding to the type 4 of Potter’s classification (Fig. 6D). The kidney in two other cases was normal except for mild hydronephrosis (Cases 2 and 6). Hydronephrotic kidneys were seen in eight of ten cases and a horseshoe kidney (Fig. 3D) in Case 12. Hydroureter was found in ten cases, of which seven were bilateral and three were unilateral. The only case with no remark- Table 1 Clinical and biometrical data of the prune-belly syndrome

~ Autopsy Sex Type of Gestation** Body C-H C.f. Size of Age of Case Year Number Birth month Weight(g) (cm) Abdomen (cm) U.B. (cm) Mother or week

~ 1 1952 T-1768 M S.B. 4M 23.5 9.7 N.E. 3.4 X 4.0 *

2 1955 T-2204 M S.B. 1OM 3750 32.9 53.5 11.0 X 14.0 *

3 * T-2396 M S.B. 7M 2410 38.5 N.E. N.E. 21

4 1959 T-2850 M * 1OM 3140 49.0 34.8 5.0 x 5.0 *

5 1965 HG-1016 M N.D. 9M 2920 46.2 45.2 15.0 X 12.0 *

6 1966 HG-1172 M S.B. 23W 920 26.1 32.9 10.0 x 11.0 *

7 1967 HG-1371 F * 7M 1900 38.0 30.0 7.0 X 7.0 *

8 1977 HG-3744 F S.B. 1OM 2900 43.0 37.0 10.0 X 8.0 22

9 1978 HG-3979 M N.D. 34w 1700 47.0 31.0 7.5 x 5.5 23

10 1980 HG-4 16 3 M N.D. 1OM 3030 49.6 47.7 N.E. 26

11 1981 HG-4473 F S.B. 39w 2380 48.3 32.1 6.0 x 5.5 28

12 1982 FN-65 M N.D. 31W 2580 41.2 40.0 13.0 x 11.0 29

~ S.B.: Still birth, N.D.: Neonatal Death, C-H: Crown to heel length C.f.: Circumference, U.B.: Urinary Bladder, N.E.: not examined *: No information was available, **: ovulation age

W 4 K. Kawarnoto et al. able change in the ureter was Case 1 that was born in 4 months of pregnancy. In most cases affected, however, the ureter was elongated, tortuous and attenuated. Some cases were associated with unilateral or bilateral absence of the ureterovesical orifice. Histologic observation of the ureter revealed the absence or hypoplasia of smooth muscles with moderate to severe fibrosis of the ureteral wall (Fig. 7). A urachal cyst was present in two cases (Cases 11 and 12). Of 12 cases, nine were associated with urethral atresia, two had a normal urethra without stenosis, dilatation and urethral valves, and one was not examined. c) Genital organs. In all nine males, both testes were found in the abdominal cavity and were located in an upper position than in normal. Furthermore, a hypoplastic penis was found in four cases and absence of the prostate in two cases. Of three females, uterus bicornis unicollis was found in two cases (Fig. 3B) and the other case showed didelphic bicornis and double vagina with atresia (Fig. 3C). Furthermore, absence of the external genitalia was found in two cases (Cases 7 and 8) and female pseudohermaphroditism which showed hypertrophy and elongation of the clitoris and swelling of the vulva was found in one case (Case 11). Hypoplasia of the ovary was found in two cases (Cases 7 and 8). 2. Associated anomalies (Table 3) a) Digestive system. Among digestive anomalies, imperforate anus was most frequent (8 cases) and all of them showed rectal atresia according to Gross’s classification. Recto-vesical fistula was also frequent (7 cases), but complete persistence of the cloaca was not found. Common mesentery was observed in three cases. Malrotation, Meckel’s diverticulum, ectopic pancreas, and rectourethral fistula were observed in one case each. b) Ysteomuscular system. The most frequent anomaly was metatarsus varus or talipes calcane- ovarus (7 cases). Three cases had spina bifida. Congenital dislocation of the hip was found in two cases. Furthermore, amputation of the leg, genu recurvatum, and absense of the thumb were found in one case each. c) Cardiovascular system. Five cases were associated with cardiovascular anomalies including coarctation of the aorta, double outlet right ventricle, persistent truncus arteriosus (PTA), persistent left superior vena cava (PLSVC), PDA and isolated VSD. d) Miscellaneous associated anomalies. Abnormal lobulation and hypoplasia of the lung were found in five cases each, of which one case (Case 11) had a Potter’s face. The association with omphalocele was found in four cases. An accessory spleen was observed in three cases. Two cases had a single umbilical artery.

DISCUSSION

There has been much speculation on the pathogenesis of the prune-belly syndrome, but there seems to have been no unified opinions to date. As to the pathogenesis of a prune-like abdomen whlch is one of the principal anomalies of this syndrome, several hypotheses have been proposed, i.e., (1) primary mesodermal errors (Lattimmer, 1958; Nunn and Stephens, 1961; Mininberg et al., 1973; Duckett, 1980; Straub and Spranger, 1980), (2) primary urinary tract abnormalities (Silvermann and Huang, 1950; Pagon et al., 1979; Monie and Monie, 1979, Lubinsky, 1980, Pinto et al., 1982), (3) raised intraabdominal pressure (Potter and Table 2 Major anomalies in twelve cases of the prune-belly syndrome

Case 1 2 3 4 5 6 I 8 9 10 11 12 Sex M M M M M M F F MM F M

Prune-like abdomen + + + + + + + + + + + + Aplasia (++) and hypoplasia (+) of muscle + + * * + + + * ++ + * ++

Dysplasia, multicystic Subcapsular cysts Hydronephrosis Horseshoe kidney Hydroure ter Giant bladder Urachal cyst Urethral atresia

Cryptorchidism + + * + + + + + + Hypoplastic penis + M

111 E Absence of prostate + 8 Hypoplasia of testis -0 .; .; Uterus duplex + + + 5 2 ~ Vaginal atresia + m E Hypoplastic ovary + + k Absence of external genitalia + + Hypertrophy of clitoris +

Marks show the presence (+) or absence (-) of anomaly otherwise stated. *: No information was available 6 K. Kawamoto et al.

Table 3 Associated anomalies in twelve cases of the prune-belly syndrome

I. Digestive system 111. Cardiovascular system imperforate anus 8 coarctation 1 recto-vesical fistula I DORV 1 common mesentery 3 PTA 1 malrotation 1 PLSVC 1 Meckel’s diverticulum 1 PDA 1 ectopic pancreas 1 VSD 1

11. Osteomuscular System IV. Miscellaneous associated anomalies metatarsus varus 7 Lung abnormal lobulation 5 spina bifida 3 hypoplasia 5 LCC 2 Omphalocele 4 amputation of leg 1 accessory spleen 3 genu recurvatum 1 Single umbilical artery 2 absence of thumb 1 Potter’s face 1 hemivertebra 1

Craig, 1975; Pinto et al., 1982) and (4) transient hydrops of abdominal wall in the fetal period (Lubinsky and Rapoport, 1983). Embryologically, the principal components of the abdominal musculature arises from the lower thoracic and first lumbar segments of somitic mesoderm during the 4th week of gestation (Duckett, 1980) and the individual muscles are differentiated as early as the seventh week (Gray and Skandalakis, 1972). In the present cases, the interfered portions may range from the lower thoracic somites to the lower lumbar somites, because hypoplasia or aplasia of the abdominal muscles was found in both upper and lower regions of the abdomen in all cases and also the absence of chest wall musculature was noted in one case. Pinto et al. (1982) suggest that muscle necrosis or fibrosis within the anterior abdominal muscle is a result of ischemia due to venous obstruction following raised intra-abdominal pressure. However, the muscle fibers in the prune-belly syndrome are either absent or of the “embryonal type”, broaden- ed, not striated, with loss of coherence in Z bands and mitochondria1 abnormalities on electron microscopic studies (Nunn and Stephens, 1961; Mininberg et al., 1973). In the present cases, there was no muscular degeneration nor necrosis of the abdominal walls, although electron microscopic examination was not performed. In terms of the pathogenesis, this histopathological finding is not so important for supporting any of the hypotheses, because necrosis and fibrosis are a secondary phenomenon in view of the fact that, when healed, necrosis is no longer observed suggesting sub- sequent regeneration. Anyhow the muscular hypoplasia may result from the primary developmental defect of the myotome during as early as the 4th week, and also from the secondary effect such as raised intraabdominal pressure in a later period of gestation. As to the development of urinary tract anomalies, the authors assume that the primary or secondary developmental defect (hypoplasia) of both genital tubercle and urorectal septum may occur during the same somitic period. Hypoplasia of the genital tubercle may provoke urethral hypoplasia Prune Belly Syndrome I or obstruction and absence of external genitalia. Giant bladder, hydroureter, multicystic kidney, renal dysplasia and oligohydramnios may be caused secondarily by urethral obstruction. Further, oligohydramnios may be a cause of extremital malformations as observed in the present cases. The wall of giant bladder showed thickening of musculature in most cases presented. This finding may be due to the reaction to the elevated intravesical pressure. On the other hand, hypoplasia of the urorectal septum may provoke rectovesjcal fistula and imperforate anus. Furthermore, the dorsal deviation of the urorectal septum may cause an unequal septation of the cloaca and subsequently may provoke a large bladder and imperforate anus. However, urethral obstruction may also occur as a primary defect. Pagon et al. (1979), who describe the “urethral obstruction malformation complex”, have proposed a hypothesis that the abdominal wall defect characterizing the prune-belly syndrome is provoked by urethral obstruction ensuing bladder distension. This hypothesis is agreeable in many cases, but it gives rise to some contradictions against the following facts: (1) The prune-like feature of the abdominal wall is not always accompanied by urethral obstruction; (2) It is impossible to give monistically an account of associated genitourinary tract anomalies, such as absence of external genitalia and rectovesical fistula; and (3) The development of abdominal muscles has already begun before urethral obstruction occurs probably resulting from hypoplastic genital tubercle. As to the pathogenesis, such cases associated with the anomalies provoked in earlier embryonic period may be explained by the hypothesis of primary somitic defect as shown in Fig. I. Recently, an alternative view has been proposed that a pathologic development of the perianal

_____------_- __ hypoplasia 4w hypoplasia of ___------urorectal septum of myotome

7w fistula imperforate anus atrophy) persistent urachus

anomalies of deformed or 12 w

Fig. 1 Possible pathogenesis of Prune Belly Syndrome : possible primary defect 8 K. Kawamoto et al. region, that is, “caudal regression syndrome” by Lubinsky (1980) may be a primary event of the prune-belly syndrome (Hokamp and Muller, 1983). However, as regards abdominal muscular hypoplasia, they suggest that it is provoked by bladder dilatation secondary to urethral atresia. There- fore, this hypothesis is quite similar to that of urinary tract abnormalities. The prune-belly syndrome is usually associated with multiple anomalies in addition to the principal and related anomalies. In general, it is difficult to give an account of entire anomalies by only one embryological defect, and these may result from a chain reaction of embryonic tissues. We have no precise knowledge on the tissue interaction at present. In summary, having examined twelve cases of the prune-belly syndrome, the authors suggest that the prune-belly syndrome may be a spectrum of developmental anomalies according to the stage specificity mainly observed in the abdominal wall and genitourinary organs as shown in Fig. 1 and the associated anomalies may tell us the primary defect of the case encountered. Further- more, it is proper as to the triad of this syndrome to replace the term cryptorchidism with “genital anomalies” because of the existence of female cases.

REFERENCES

Duckett, J.W. Jr. (1980) 61. Prune-Belly Syndrome. tourinary anomalies: A report of 22 cases. J. Pediatric Surgery, (Holder T.M. ed.), W.B. Saund- Urol., 79: 343-352. ers, Philadelphia, 802-815. Lubinsky, M.S. (1980) Female pseudohermaphrodit- Eagle, J.F. and Barrett, G.S. (1950) Congenital defi- ism and associated anomalies. Am. 5. Med. Genet., ciency of abdominal musculature with associated 6: 123-136. genitourinary abnormalities. A syndrome. Pedi- Lubinsky, M.S. and Rapoport, P. (1983) Transient atrics, 6: 721-736. fetal hydrops and “prune belly” in one identical Frohlich, F. (1839) Der Mangel der Muskeln ins- twin. N. Engl. J. Med., 308: 256-257. besondere der Seitenbauchmuskeln. Dissertation. McGovern, J.H. and Marshall, V.F. (1959) Congeni- Wiirzburg C.A., Zurn. Cited from: Williams, D.I. tal deficiency of the abdominal musculature and and Burkholder, G.V. (1967) The prune belly syn- obstructive uropathy. Surg. Gynecol. Obstet., drome. J. Urol., 98: 244-251. 108: 289. Gray, S.W. and Skandalakis, J.E. (1972) The anterior Mininberg, D.T., Montaya, F., Okada, K., Galioto, body wall. Embryology for sugeons: The Embryo- F. and Presutti, R. (1973) Subcellular muscle logical Basis for Treatment of Congenital Defects. studies in the prune belly syndrome. J. Urol., W.B. Saunders, Philadelphia. 109: 524-526. Hirao, Y., Okajima, E., Matsushima, S., Hayashi, I., Monie, I.W. and Monie, B.J. (1979) Determinants of Hiraoka, K., Yamaguchi, R., Ou, M., Yoshida, K., the prune belly syndrome. J. Pediatr., 95: 1084. Omori, T., Hisaya, Y., Hiroshi, K. and Kitamura, Nunn, I.N. and Stephens, F.D. (1961) The triad syn- H. (1974) An autopsy case of prune belly syndrome: A composite anomaly of the abdominal drome. J. Nara Med. Ass., 25: 314-327. (Japa- wall, urinary system and testes. J. Urol., 109: nese) 5 24-526. Hokamp, H.G. and Muller, K.M. (1983) Prune belly Osler, W. (1901) Congenital absence of the abdominal syndrome and female pseudohermaphroditism. musculature, with distended and hypertrophied Pathol. Res. Pract., 177: 77-83. urinary bladder. Bull. Johns Hopkins Hosp., 12: Housden, L.G. (1934) Congenital absence of the ab- 331-333. dominal muscles. Arch. Dis. Child., 9: 219-234. Pagon, R.A., Smith, D.W. and Shepard, T.H. (1979) Lattimmer, J.K. (1958) Congenital deficiency of the Urethral obstruction malformation complex: A abdominal wall musculature and associated geni- cause of abdominal muscle deficiency and the Prune Belly Syndrome 9

“prune belly.” J. Pediatr., 94: 900-906. Takayama, K. (1980) Prune belly syndrome with Parker, R.W. (1895) Case of an infant in whom some an extrophy of the bladder: case report, Acta. of the abdominal muscles were absent. Trans. Clin. Urol. Jpn., 26: 335-344. (Japanese) SOC.Lond., 28: 201. Cited from Williams D.I. and Silvermann, F.N. and Huang, N. (1950) Congenital Burkholder, G.V. (1967) The prune belly syn- absence of the abdominal muscles, associated with drome. J. Urol., 98: 244-251. malformation of the genitourinary and alimentary Pinto, T., Baithun, S.I., Giwan, Y.A.M. and Berry, tracts: Report of cases and review of literature. C.L. (1982) The prune belly syndrome-A possible Am. J. Dis. Child., 80: 91-124. pathogenesis. Diagn. Histopathol., 5: 197 -203. Straub, E. and Spranger, J. (1980) Prune belly syn- Potter E.L. and Craig, J.M. (1975) Kidney, ureters, drome and urethral obstruction (Letter). J. Pedi- urinary bladder and urethra. Pathology of the atr., 96: 176-778. Fetus and the Infant, Third Edition, (Potter, E.L. Welch, K.J. (1979) Abdominal muscular deficiency and Craig, J.M. ed.), 434-473. syndrome (prune belly). Pediatric Surgery, Vol. 11. Sakuma, Y., Ohinata, M., Akasaka, T., Numasato, S., (Ravity M.M. et al. ed.), Year Book Medical Pub- Kubo, T., Ohori, T., Izutsu, T., Kimura, H. and lishers, Chicago, 1191-1203. 10 K. Kawamoto et al.

Fig. 2 External appearances of the prune-belly syndrome. A. Case 1.- Male, 4M. Markedly distended urinary bladder is seen. Imperforate anus is also associated. B. Case 10. Male, 10M. Markedly distended and wrinkled abdomen with omphalocele is seen. C. Case 11. Female, 39W. Moderately distended and wrinkled abdomen is seen. Potter’s face, hypertrophy of clitoris, imperforate anus and various abnomalities of the extremities such as left genu recurvatum and adduction of bilateral feet are also associated. D. Case 12. Male, 37W. Markedly distended and wrinkled abdomen is seen. Absence of the external genitalia, imperforate anus and various abnormalities, such as right floating thumb, right metatarsus varus and left split foot are.also associated. Prune Belly Syndrome 11

Fig. 3. Macroscopic findings of abnormal urogenital organ. A. Case 5. Giant bladder (b), marked hydroureters (u), urethral atresia, crytorchidism (t), recto-vesical fistula (rvf) and multicystic kidneys with hydronephrosis (k) are seen. Scale bar is 1 cm in Fig. 3. B. Case 8. Giant bladder (b), hydroureters (u), urethral atresia, recto-vesical fistula (rvf), multicystic kidneys with right hydronephrosis (k), hypoplastic ovaries (o), uterus bicornis unicollis with the agenesis of left horn (ub) and vaginal atresia are seen. C. Case 11. Giant bladder (b), left hydroureter (u), urachal diverticulum (ud), urethral atresia, hypoplastic left kidney (lk), multicystic right kidney (rk), didelphic uterus (du), double vagina with vaginal atresia and recto-urethral fistula (ruf) are seen. D. Case 12. Giant bladder (b), hydroureters (u), horseshoe kidney with multiple cysts (k) and cryptorchidism (t) are seen. Recto-vesical fistula and absence of urethra and prostate are associated. 12 K. Kawamoto et al.

Fig. 4 Microscopic findings of anterior abdominal wall. A. Severe hypoplasia, Case 6. A thin muscle bundle (m) is embedded in thick collagenous bundles (c). Masson’s trichome stain. X5 B. Extreme hypoplasia, Case 2. Supraumblical region. Sparse muscle fibers are seen in thick collagenous bundles (c). Masson’s trichome stain. XI0 C. Aplasia, Case 2. Infraumblical region. Edematous thickening of abdominal wall with hyperplasia of blood vessels is noted. No muscle fibers are seen and collagenous bundles (c) are formed. Masson’s trichome stain. X5 D. Aplasia, Case 9. No muscle fibers are seen. Thick collagenous bundles (c) are seen between subcutane- ous tissue and peritoneum. Masson’s trichome stain. X5 Prune Belly Syndrome 13

Fig. 5 Microscopic findings of urinary bladder. A. Case 12. Markedly thickened wall of the bladder with muscular hyperplasia. Note remarkable submucosal fibrosis. Masson’s trichome stain. X5 B. Case 4. Normal or rather thinner wall of the bladder. Mild intramuscular fibrosis. Masson’s trichome stain. X5 14 K. Kawamoto et al.

Fig. 6 Microscopic findings of kidney. A. Case 11. Renal dysplasia characterized by cystic dilatation of tubules with scattered glomeruli and an increase of interstitial connective tissue. Masson’s trichome stain. X5 B. Case 5. Renal dysplasia characterized by islands of cartilage, immature mesenchyme and diminished glomeruli. Masson’s trichome stain. X5 C. Higher magnification of B. Islands of cartilage, immature glomeruli, interstitial lymphocytic infilatra- tion and fibrosis. Masson’s trichome stain. X50 D. Case 4. Multiple cysts in the subcapsular region. Note normal glomeruli and Bowman’s capsules. Mas- son’s trichome stain. X5 Prune Belly Syndrome 15

Fig. 7 Microscopic findings of ureter. A. Case 5. Generalized attenuation of the ureteral wall with severe fibrosis. Rudimentary muscle fibers are noted within collagen bundles. Masson’s trichome stain. X 10 B. Case 4. Focal thickening of the ureteral wall with hyperplastic smooth muscles and moderate fibrosis. Masson’s trichome stain. X10