Mucinous urethral caruncle

MUCINOUS URETHRAL CARUNCLE* AHMAD ELRADAWI, M .D ., M .Cii. WALTER E . MALHOSKI, M .D . IRWIN"N . FRANK, M .D . From the Department of Pathology and Division of Urology . University of Rochester Medical Center, Rochester, New York

ABSTRACT -A case of urethral caruncle, composed exclusirebt of nutcin-secreting colonic-htpe glands and believed to be the first on record, is described. The lesion presented clinically its an Ordinary carmine and was treated by local excision . The histogenesis of the lesion is discussed, and its probable origin from an intraurethral cloacogenic colonic gland rest is proposed .

Urethral caruncle is classically described as a fleshy-, pink to red . peduneulated or sessile, polypoid growth which bleeds readily on the slightest trauma and is located internally or externally along the posterior or lateral margin of the external female urethral meatus. Three histologic variants of caruncle are universally recognized . namely, papillomatous, angiomatous, and granuloin atous,' with transitions hum one variety to the other being occasionally encoun." tered The papillomatous (epithelial) caruncle is characterized by marked epithelial hyperplasia and a core of loose connective tissue containing variable amounts of small blood vessels and inflammatory cells . The epithelium is stratified squamous (with or without keratinization), transitional, or both . Hvperplasia of Skene glands and duels is prominent in some papillomatous caruncles, once designated as adenomatous .a Numerous capillary and cavernous vascular spaces within the core predominate in the angiomatous caruncle, which usually has a hyperkeratinized stratified squamous epithelium . The granulonlatous caruncle is composed of granulation tissue, with intense inflammatory cell infiltration and attenuation or denudation of the surface epithelium . The case herein described introduces a previously unrecognized type of urethral caruncle 'Supported In Grant Ca-11198-05 and the Iienrs- C . Ruassell 1, oloec Research tlmd .

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composed of an adenomatous prolifi ration of inucin-secreting colonic-type glands . Case Report A thirty-seven-year-old black wwnan was seen with a polypoid fleshy red lesion at the external urethral meatus, discovered by her funil physician on routine physical examination . She had a history of occasional bleeding after intercourse, without concomitant urinary symptoms, and had had a urinary tract infection successfitlly treated with sulfa drugs many Years previously . On examination, the lesion was located on the left side of the external urethral meatus and had the clinical characteristics of urethral Cal-Uncle (Fig . 1). The urethra readih accepted a 24 F sound . There were no other positive physical findings .. and findings on urine examination were negative. At cvstoscopy, the bladder and urethra were normal except for patchy trigonal and internal mcatal congestion . The caruncle was excised at the end of the procedure, and the patient was discharged the same evening . She never returned for follow-up visits . The specimen consisted of a 0 .6 by 0 .4 by 0 .3-cm . polvpoid mass of fleshy tissue, with a smooth, reddish, focally hemorrhagic surface, The cut surface was flesh colored with areas of mucoid appearance . Microscopically_ the lesion consisted of numerous muem-secrchin" glands, separated by moderately dense stroma and covered by focally ulcerated keratinized stratified srtuarnous epithelium (Fig . 2) . The stroma con-

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Preoperative photograph of caruncle (arrow) on left side of external urethral meatus, which is reduced to narrow curvilinear slit-like orifice . FIGURE 1 .

FIGURE 2 . Caruncle is composed of mueinsecreting glands, with moderately dense stroina containing several rnucin lakes, and is covered by nonkeratinizing stratified squamous epithelium . Hematoxylin-eosin ; cross-section of entire lesion .

FIGURE 3 . Glands are mucin-secreting with tall col. ,5W umnar epithelium and abundant goblet cells, identical to colonic rnucosa . Moderately vascularized stroma is infiltrated by chronic inflammatory cells, primarily lymphocytes and plasma cells, and contains lakes of mucino s material (ml) . One lake is densely infiltrated by neutrophils and appears as rnicroabscess (ab) . Hematoxylineosin; reconstructed from four microscopic fields; scale = 30 µin .

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tained many small vascular channels and a dense lymphoplasmacytic infiltration (Fig . 3), with occasional eosinophils, neutrophils, histiocytes, and mast cells . The glands were lined with a single layer of tall columnar and goblet cells, identical to those of colonie mucosal crypts, with no stratified columnar, transitional, or prostatic gland-type components (Fig . 3) . Some disrupted glands were continuous with stromal lakes of secretion, containing scanty cellular debris, remnants of glandular epithelium, and neutrophils . Sonic lakes were lined by markedly compressed epithelium, and many were walled off directly by the surrounding stroma (Figs . 2, 3) . Prominent neutrophilic infiltration of a few mucin lakes and subsurface glands produced focal microabscesses (Fig . 3) .

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To characterize the type of glandular epithelial cells, mucin secretion, and stroma, the following special stains were obtained : periodic acid-Schiff (PAS), diastase-PAS, mucicarmine, alcian blue-containing stains (Elbadawi hexachrome" and Kreyberg), modified Wilder reticulin, and argentaffin . The material within glandular lumina, goblet cells, and mucin lakes had the tinctorial qualities of colonic-type mucin, being strongly diastase-PAS, mucicarmine, and alcian blue positive, and slightly argyrophilic (Fig . 4A to D) . The glandular epithelium included a few Paneth cells with apical bright red granular cytoplasm (Fig . 4C), but enterochromaffin (argentaffin-positive) cells were absent . The stroma contained abundant reticulin fibers, some smooth muscle cells, little collagen, and

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Staining properties of nnrcin secretion within gland lumina and goblet cells ; scale = .50 tun . (A) Vivid purple-red staining with diastase-PAS . (B) Bright pink staining by mucicarmine . (C) Strong alcian blue positive reaction with emerald green color (Kreyberg stain) : two glands contain Paneth-type cells, with red apical cytoplasmic granularity (arrows) . (D) Fine black granularity of goblet cell mucin reflects its slightly argyrophilic property (reticulin stain) ; stroma contains rich reticrlin fiber (black-staining) network . circumferentially condensed as a basement membrane-like lamella around each gland . FIGURE 4 .

FIGURE 5 . (A) Early stromal mucin lake resulting from focal disruption of gland lining and enclosing reticulin fiber lamella, with extraglandular leakage of mucin secretion into adjacent stroma (arrow) . Reticulin : scale - 50 tun . (I Established stromal mucin lake . walled off directly by surrounding stroma around most of its circumference . contains residual islands of degenerating epithelium (arrows) . Kreyberg stain : scale = 50 µm .

no elastic fibers . Reticulin fibers were condensed as circumnferential basement mernhranc-like lamellae at the interface between glands and stroma (Fig . 4D) . Mucin lakes resulted from rupture of glandular epithelial cells overdistended with secretion, disruption of

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periglandular reticulin lamellae, and leakage of secretion into the adjacent stroma (Fig . 5A, B) . Extraglandular accumulation of secretion resulted in compression, degeneration, and ultimately loss of glandular lining epithelium (Figs . 3 and 5B) .

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Comment The lesion herein described is the first example in the literature of a urethral caruncle composed exclusively of mucin-secreting colonictype glands . The designation of' mucinous caruncle is suggested to avoid confusion with the adenomatous variant of papillomatous caruncle characterized by marked Skene gland or duct hyperplasia .s Histogenetically the mucinous caruncle may represent : (1) a hyperplastic or neoplastic proliferation of urethral or paraurethral (Skene) glands ; (2) a metaplastic transformation of urethral epithelial structures ; or (3) a heteroplastic growth in au intraurethral embryonal rest of colonic-type glands. Urethral glands in the form of lacunar mucosal invaginations normally occur along the entire length of the female urethra. 2 They are the homologue of Littre glands of the male urethra, being lined by transitional epithelium with a paraluminal layer of cuboidal or columnar, and mucin-secreting goblet cells . It is conceivable that the mucinous caruncle represents marked hyperplasia or an adenoma of this goblet cell component, which had outgrown and replaced the predominantly transitional lacunar epithelium . However, on this basis it would be difficult to explain a lesion at the external meatus, which normally has an exclusively stratified squamous lining, particularly since none of the glands of the canmcle contained transitional epithelium, even nricrofbcally . Origin from the homolateral Skene duct or gland is equally difficult to accept since the mucinous caruncle was completely devoid of prostate-type glands . Development of the mucinous caruncle as a result of metaplasia in urethral epithelium would place it in the category of "glandularis" urothelial lesions of the intestinal type .' The single documented case of urethritis glandularis on record involved the entire posterior urethra of a fifty-five-year-old man with long-standing urethral stricture, and was complicated by urethral adenocarcinoma . 6 A metaplastic origin is highly unlikely since urothelium-lined mucosal invaginations with such a potential arc never seen at the external urethral meatus . Moreover, the mucinous caruncle had no surface glandular epithelium, nor did it contain transitional urothelial elements in any of its component glands . Heterotopia of colonic mucosa in the urethral wall can easily he explained on embryologic basis . The female urethra develops from the

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vesicourethral canal portion of the urogenital sinus, lying anterior to the urorectal septum, with the rectum forming the posterior portion .' It is easily conceivable that cloacogenic colonic gland rests become sequestered into the urethra at some stage during its embryonic development . Rests of this type have recently been described as incidental histologic findings in the wall of female urethral diverticula .' The tinctoria l qualities of secretion in the mucinous caruncle, the encirclement of its glands by condensed reticulin lamellae, and the presence of smooth muscle cells in its stroma favor an origin from an intraurethral cloacogenic rest . The lack of stromal elastic fibers not only favors such an origin, but also militates against origin from indigenous urethral structures . The mucinous caruncle thus probably represents an intraurethral cloacogenic colonic gland rest, which has undergone proliferation to form an adenoma . This readily accounts for the extreme rarity of the lesion and its histologic features . If the mucinous caruncle originated from indigenous urethral epithelial elements by a hyperplastic, neoplastic, or metaplastic process, it would be expected to he a relatively common lesion and perhaps to occur as frequently as comparable lesions of the urinary bladder, particularly in view of the frequency of urethral infection in the female . A heteroplastic origin of the mucinous caruncle would easily explain the absence of transitional epithelium in its surface epithelium and glands, the presence of stronial smooth muscle cells, and the lack of stromal elastic fibers . Department of Pathology, SUNY . Upstate Medical Center 750 E . Adams St . Syracuse, New York 13210 (DR . ELBADAWI) References 1. 2 . llerbut PA : Urological Pathology . London, henn Kempton, 1952, vol . 1, pp . 96-102 . 3. Foot NC : Pathology in Surgery . Philadelphia, J . B . Lippincon Co ., 1945, p . 304. 4 . F.Ihadawi A : 11exachromc modification of Movat s stain, stain Techn. 51 : 249!,1976) . 5. Emmett JL, and McDonald JR : Proliferation of glands of the oiinaw bladder siurulating malignant neoplasm, J . Urol . 48 : 257 (1942) . 6 . Posso MA, et a( : Mm:i ions adenocareinoma of the urethra : report of a case associated with urethritis glandularis, ibid. 8a': 944 (1961" . 7 . Benjamin J, rf al : Uiethral diverticulum in adult female, Urologv3 : 1 (1974)_

UROLOGY NOVEMBER 1978 , VOLUME XLI . NUMBER 5