Case Report

Adenosquamous Carcinoma of the Colon An Immunocytochemical and Ultrastructural Study Report of Two Cases and Review of the Literature

THEODOSIOS E. KONTOZOGLOU, M.D.,* TERENCE N. MOYANA, M.D.S"

Kontozoglou TE, Moyana T. Adenosquamous carcinoma of the colon--an immunocytochemical and ultrastructural study: report of two cases and review of the literature. Dis Colon Rectum 1989;32:716- 72I.

This paper presents two cases of adenosquamous carcinoma of the colon and brings to 39 the total number documented in medical litera- ture. The concurrent glandular and sqnamous differentiation of the tumor cells was demonstrated by immunocytochemistry and electron microscopy. Evaluation of the biologic characteristics of all the reported cases suggests that malignant squamous elements in colonic carcinomas behave more aggressively than their glandular counter- parts. In contradistinction from the pure squamous-cell carcinoma of the colon, adenosquamous carcinoma does not show the same predilec- tion for the right colon. [Key words: Adenosquamous; Carcinoma; Colon; Immunocytochemistry; Ultrastructure]

ADENOSQUAMOUS CARCINOMA of the colon is a rare

neoplasm. Exc lud ing all lesions distal to a level arbitrar- ily chosen as 7 cm above the dentate l ine, Comer et al., 1 in a review study s p a n n i n g 60 years, f ound eight cases of squamous-ce l l and 12 cases of adenosquamous carci- n o m a cons t i tu t ing 0.025 to 0.05 percent of all m a l i g n a n t

colonic a n d uppe r rectal tumors. Cr issman, 2 in a s imi lar study, identif ied five adenosquamous carc inomas out of 5969 colonic cancers. Whi le its locat ion in the anorectal area is no t unexpected in view of the nat ivi ty of bo th g l andu l a r a n d s q u a m o u s ep i t he l i um to that ana tomic site, the occurrence of the t umor at more p rox ima l levels

Address correspondence to Dr. Kontozoglou: Department of Pathol- ogy, St. Joseph's Hospital, P.O. Box 5777, London, Ontario, Canada N6A 4L6.

From the Department of Pathology, St. ]oseph's Hospital, London, Ontario,* and

University Hospital, Saskatoon, Saskatchewan, Canadat

of the co lon has generated several his togenet ic explana-

tions, x-5 T h e biologic characteristics of this neop la sm have no t

been fully elucidated due to the pauci ty of documented cases. We herein report two pat ients wi th adenosqua- mous ca rc inoma of the colon who were examined for the first t ime both wi th immunocy tochemis t ry a nd electron microscopy; in addi t ion, we review the li terature and a t tempt to del ineate the c l in icopa thologic features that

characterize this neoplasm.

R e p o r t of T w o Cases

Patient 1: A 74-year-old, diabetic, white woman presented with a six-month history of lower abdominal pain and progressive weakness. She had sustained an anterior myocardial infarct seven years pre- viously, but past medical history was negative for gastrointestinal ailments. On examination the patient was febrile, with a firm, lobu- lated mass in the left paraumbilical area and a hard, easily palpable liver. Laboratory investigations revealed a hemoglobin of 104 gm/L, and moderately elevated liver enzymes. Barium studies disclosed a filling defect in the sigmoid colon and CT scan showed multiple solid lesions in the liver. Liver biopsy showed a poorly differentiated meta- static carcinoma. The patient was managed conservatively until her death, four weeks after admission. At autopsy, the main findings were localized in the abdomen; there was a fungating tumor mass in the sigmoid colon, measuring approximately 5 • 3 cm, located 20 cm above the dentate line; metastases to mesenteric lymph nodes and liver were extensive. No other neoplasms were present.

Patient 2: An 81-year-old white woman presented with increasing constipation, abdominal pain, and generalized loss of strength. Past

716

Volume 32 Number 8 A D E N O S Q U A M O U S C A R C I N O M A OF T H E C O L O N 717

FIG. 1. Poorly differentiated squamous cells fo rming pearl-like groups (hematox- ylin and eosin; )< 170).

medical history was notable only for an appendectomy performed in childhood. O n examinat ion, a large, hard mass was found in the r ight lilac fossa. Exploratory laparotomy revealed a cecal mass measur ing 9.0 X 8.0 X 6.0 cm. Several enlarged l y m p h nodes were present in the mesentery, bu t no distant metastases were found. A r ight hemicolec- tomy was performed. The pat ient uneventful ly recovered and is pres- ently alive 11 m o n t h s after the operation.

Materials and Methods

The tissue from both patients was fixed in 10 percent neutral buffered formaldehyde, and routinely processed in paraffin. Sections were stained with hematoxylin and eosin, periodic acid Schiff-alcian blue at pH 2.5, muci- carmine, Cherukian-Schenk (argyrophil), and Fontana- Masson methods. Immunohistochemistry was carried out using the avidin-biotin complex method. 6 Monoclonal antibody for low molecular weight keratin (LMWK) (Becton Dickinson, Mountain View, CA) and polydonal antibodies for high molecular weight keratin (HMWK) (Dako, Santa Barbara, CA) and carcinoembryonic antigen (CEA) (Dimension k Mississauga, ~Ontario) were used. Wet formalin fixed tissue was transferred to 2 percent glutaraldehyde, post-fixed in osmium tetroxide, and embedded in epoxy resin. Ultrathin sections were cut with a diamond knife, stained with uranyl acetate and lead citrate, and examined by transmission electron microscopy.

Results

The histopathologic features of both tumors were sim- ilar. There was proliferation of malignant glandular and pseudoglandular structures producing mucin admixed with irregularly shaped islands of eosinophilic, keratiniz-

ing squamous cells. The first (autopsy) case was less differentiated with the squamous cells diffusely mixed with the glandular elements, in many areas themselves forming adenomatous structures. Squamous islands and pearls with central keratinization were present in adja- cent areas (Fig. 1). The second case showed better differen- tiation of both components. Glandular structures ap- peared to gradually change by individual cell keratini- zation to compact interconnecting squamous-cell groups with occasional central keratinization (Fig. 2). Intercellu- lar bridges were rather inconspicuous and difficult to visualize.

The first case was Dukes' stage D and the second stage C. In both cases, the metastases were similar histologi- cally to the primaries; in particular it was apparent that both tumor components were present in the metastases, although the degree of differentiation was lower.

Special stains showed large amounts of a mixture of mucins in the well-differentiated glandular areas. Both neoplasms were argyrophil and argentaffin negative.

CEA immunopositivity was seen primarily in the glandular component and in scattered groups of squa- mous cells. Low molecular weight cytokeratin was strongly positive in both glandular and squamous ele- ments; scattered, markedly keratinized squamous malig- nant cells, as well as occasional cells lining glandular structures, immunostained for high molecular weight cytokeratin (Fig. 3). Chromogranin positivity was present in some cells at the base of normal or dysplastic colonic crypts adjacent to the tumor, but not in the malignant cells.

Electron microscopy confirmed the presence of concur-

Dis. Col. & Rect. 7 ] 8 KONTOZOGLOU AND MOYANA August 1989

FIG. 2. Glandular elements on the left and squamous on the right side (hematox- ylin and eosin; )< 55).

rent glandular and squamous differentiation in the same cells. Both cases showed similar features; in the autopsy case, cellular detail was less well-preserved, but evidence of glandular and epidermoid differentiation was present. The cells were held together by tight junctions and numerous desmosomes; intercellular lumina bordered by microvilli were present (Fig. 4). Intracellular lumina also were seen, together with long filamentous core rootlets and glycocalyceal bodies (Fig. 5). Intracytoplasmic mu- cous granules and electron-dense bundles or sheaves of tonofilaments (tonofibrils) were often identified in the same cell (Fig. 6).

Neurosecretory granules were searched for, but not found in either case.

Discussion

Since the original report by Herxheimer 7 in 1907, 36 other cases of adenosquamous carcinomas of the colon have been described, l-5, 8-17 albeit under a variety of names such as adenocancoid) 5 adenoacanthoma, 1-3 and poly- morphous epithelioma. 18 Even today, the terminology of tumors containing both squamous and glandular ele- ments, involving not only the colon but also other sites, is obfuscated by the loose and interchangeable use of terms such as mucoepidermoid and adenosquamous 19 (e.g., esophagus) or metaplastic carcinomas 2~ (e.g., breast).

As contemporari ly defined, an adenosquamous car- c inoma is a tumor in which both the glandular and squamous components are mal ignan t and capable of

FIG. 3. High molecular weight cytokera- tin focally immunostaining squamous cells amidst glandular elements (ABC; X 136).

Volume 32 Number 8 A D E N O S Q U A M O U S C A R C I N O M A O F T H E C O L O N 719

FIG. 4. Electron micrograph showing apical microvilli (mv), tonofibrils (t), tight junctions, and desmosomes (arrows) (X 16000).

metastasizing19; in contrast, an adenoacanthoma is an adenocarcinoma with areas of squamous, metaplastic, nonmal ignant epithelium. 5 The term mucoepidermoid should be used for carcinomas, with a distinct histomor- phology, arising in secretory glandular structures such as the salivary glands. The term metaplastic carcinoma has already fallen into disuse and should be discontinued altogether. 21

The criteria for the diagnosis of adenosquamous car- c inoma of the colon exempt all lesions located distal to a level of 7 cm above the dentate line; so-called collision tumors, in which the squamous component is either metastatic from a distant pr imary or arises in fistulous tracks connected to the bowel, should also be excluded.

Several theories have been proposed to account for the origin of adenosquamous carcinoma of the colon. The presence of heterotopic embryonic rests of squamous epi thel ium in the colonic mucosa as a possible source of origin of adenosquamous carcinoma of the colon has not been substantiated. 5,17 Direct transformation of glandu- lar cells into squamous cells has also been put forward, zz

Squamous metaplasia in colonic adenomas is an infre- quent, but well-recognized, phenomenon.17, z3-z9 It has been proposed that the mal ignant squamous component may arise from foci of squamous metaplasia in colonic adenomas in a manner similar to the adenoma-carcinoma sequence.17 The incidence of squamous differentiation in colonic adenomas was 0.4 to 0.6 percent in two stud-

FIG. 5. Intracellular lumen bounded by microvilli; glycocalyceal bodies are pres- ent (X 6000).

Dis. Col. & Rect. 720 K O N T O Z O G L O U A N D M O Y A N A August 1989

FIG. 6. Electron micrograph showing mucous granules (arrowhead) and tonofi- brils (arrowhead) (X 17000).

iesAT, 26 This correlates well with the stated incidence of 0.025 to 0.050 percent of squamous and adenosquamous carcinomas of the colon 1 and is in agreement with the generally accepted 10 percent incidence of malignancy in colonic adenomas. It is questionable, however, whether squamous differentiation can be considered an independ- ent risk factor for the development of malignancy regard- less of the size or the associated dysplasia of the glandular epithelium.

Recently, a unitarian concept has been proposed, sup- porting the origin of these neoplasms from a pluripotent stem cell of endodermal origin capable of multidirec- tional differentiation36 This theory suggests that the primitive intestinal stem ceils can undergo differentiation toward a multi tude of cell types, including neuroendo- crine and squamous cells. 26 This certainly will explain the presence in the colon of tumors showing a combina- tion of these elements.30, s! This proposal, despite the unfavorable statistical data, supports the contention that squamous metaplasia in colorectal adenomas is an inher- ently neoplastic phenomenon,~6, 32 which may act as an independent factor for malignant change. The much rarer occurrence of adenoacanthomas, in which the squamous component is benign and generally considered metaplastic, despite the theoretically expected higher fre- quency of such a combination, also may be evidence in favor of the neoplastic nature of the squamous compo- nent. It also should be noted, in this respect, that pure squamous-cell carcinoma of the colon, which is theoreti- cally expected to be the rarest of the three, is represented in the literature by 54 cases? 3-36 probably reflecting a higher degree of interest for what is accepted as a much rarer tumor.

Our ultrastructural and immunohistochemical results

in this study are in agreement with this hypothesis. The presence, in the same cell, of ultrastructural evidence of squamous and glandular differentiation suggests an origin from a single progenitor cell. In addition, the immunocytochemical expression by both components of low molecular weight cytokeratin and the scattered immunoreactivity for high molecular weight cytokeratin, not only by the better keratinized squamous cells, but also by gland-forming ceils, supports a single cell origin of both elements. The absence of neuroendocrine differenti- ation in these two tumors may suggest a l imit to the phenotypic plasticity of the colonic stem cell, the deter- minants of which are not presently clear.

Recently, it has been noted that pure primary squamous- cell carcinomas of the colon have a definite predilection for the right side of the colon36; this is apparently statistically significant even after taking into account the increasing incidence of colonic cancers in proximal sites. 37 From our data, we cannot discern any significant difference in the incidence of right- v s . left-sided adenosquamous carcin- oma of the colon (Table 1); this may suggest that if there is such a tendency for the pure squamous carcinoma, it is probably modulated in adenosquamous carcinoma of the colon by the presence of the glandular element.

The biologic behavior of adenosquamous carcinoma of the colon is not yet well characterized, but there is evidence to suggest that the pure squamous cell car- cinomas of the bowel or the squamous elements in adeno- squamous carcinoma of the colon behave in a more aggressive fashion than their glandular counterparts. 1,9,~7 Our review (Table 1) shows that most of the adenosquamous carcinomas of the colon reported in the literature were Dukes' stages C and D and that only 13.6 percent of the subjects were alive after a mean follow-up period of 6.9

V~,l.ln~ 32 x,,,0,., ~ AI)t.[NOSQt':\MOt;S C,.\R(3NOMA OF I'I t1: COI.ON 721

TABI.E 1. Clinicopathologic Features o] the Documented ASCCs Including the Present Two Cases

Total number (N) Age, range, and mean Male-to-female ratio Site of primary tumor:

C e c u m

Sigmoid Ascending colon Transverse colon Rectosigmoid l_J pl~r rectum I tepatic flexure

Dukes' stage: A B C D

Follow-up period

39 28-85; 59.8 years 0.86

10 8 2 2 2 2 1

(N = 26) (N = 26) (N = 27)

(N = 26) 0 4

14 8

(N = 22) 1 day to 6 years. Mean 6.9 months Only 3 of the 22 patients were still alive (13.6%)

m o n t h s ; th i s is in a c c o r d w i t h the a b o v e - c i t e d obse rva -

t ions r e g a r d i n g aggress ive behav io r . T h e s e da t a c o n t r a s t

w i t h t h o s e o f o r d i n a r y a d e n o c a r c i n o m a s in w h i c h s tage C

has a f ive-year su rv iva l o f 45 p e r c e n t a n d s tage D a m e d i a n

su rv iva l of 7 to 9 m o n t h s P 8,~9 T h e s e f igures , h o w e v e r ,

s h o u l d be i n t e r p r e t e d w i t h c a u t i o n in v iew of the s m a l l

n u m b e r of r e p o r t e d cases a n d the c h a n g i n g s t a n d a r d s of

su rg ica l p rac t i ce over the years.

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