12-20-96
	Pathologist KATHLEEN A. FUNK, DVM, Ph.D. Diplomate, American College of Veterinary Pathologists	Report Date

Twenty tissue cassettes were submitted containing distal, midline and proximal sections of hamster cheek pouch. Two cassettes per animal were each separately labelled either right or left cheek pouch. The animals were numbered 1 through 10. It was requested that the tissues be evaluated in a descriptive narrative.

METHODS

The tissues were trimmed as necessary, processed routinely and stained with hematoxylin and eosin for standard histopathologic evaluation. The grading scale used was 0 through 4 where 0=No significant change, l=minimal, 2==mild, 3=moderate and 4=severe.

RESULTS

Animal No. 1 - Right Cheek Pouch

Three sections of cheek pouch were bordered on both sides by keratinized stratified squamous epithelium. The supporting tissue consisted of variably loose to dense fibrovascular and skeletal muscle tissue. Reactive mast cells were scattered throughout the stroma. Focal minimal bronze tinted macrophages were observed below the epithelium in one section.

Animal No. 1 - Left Cheek Pouch

Three sections of cheek pouch had natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably loose to dense fibrovascular tissue. A few reactive mast cells were observed scattered throughout the connective tissue, particularly around some of the vessels.

Animal No. 2 - Right Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified epithelium on either side of skeletal muscle and variably dense fibrovascular tissue. Scattered reactive mast cells were observed throughout the connective tissue. Sparse numbers of neutrophils were observed in one section.

Animal No. 2 - Left Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified epithelium on either side of skeletal muscle and connective tissue. Scattered reactive mast cells were observed in the connective tissue. Rare swollen hypereosinophilic myofibers were observed. Sparse numbers of myofibers also had intemalization of nuclei.

Animal No. 3 - Right Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified squamous epithelium on either side of skeletal muscle and variably loose connective tissue. Perivascular mast cells were seen and some mast cells were scattered throughout connective tissue. Focal folded brown pigmented material was observed in the stroma of one section without any surrounding inflammatory reaction. One of the three sections had cleft-like large empty spaces due to separation of the loose connective tissue layer.

Animal No. 3 - Left Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified squamous epithelium on either side of skeletal muscle and variably dense connective tissue. Reactive mast cells were evenly scattered throughout the connective tissue and sometimes slightly more concentrated around congested vessels. One small perivascular focus also contained other mononuclear inflammatory cells consistent with lymphoid origin.

Animal No. 4 - Right Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium on both sides of skeletal muscle and variably loose connective tissue. Minimal subepithelial perivascular inflammation consisted of lymphoid cells and a few granulocytes admixed with mast cells. A couple of adjacent myofibers were characterized by hypereosinophilic cytoplasm and intemalization ofmyofiber nuclei.

Animal No. 4 - Left Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified squamous epithelium on either side of skeletal muscle and variably loose fibrovascular tissue. One section had a region of mild perivascular mixed inflammation comprised of plasma cells, lymphocytes and granulocytes. The latter included neutrophils and some eosinophils. Mast cells were also observed. Mild spongiosis was observed at the overlying epidermis. The keratin layer was absent from this area of inflammation. Another focal smaller area of inflammation had inflammatory cells within the epithelium and again the keratin layer was absent.

Animal No. 5 - Right Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Scattered mast cells were observed throughout the connective tissue, especially around small vessels. Focal increased density of mast cells was observed between myofibers and around vessels in one section.

Animal No. 5 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue in which there were scattered mast cells. Focal mild mixed inflammation was observed in one section. Inflammation was comprised of lymphocytes, plasma cells and granulocytes, some of which were eosinophils. Inflammatory cells were observed in the overlying minimally spongiotic epithelium. Focal keratin loss was also noted.

Animal No. 6 - Right Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Perivascular mast cells were observed. One of the sections was supported by a slightly mucinous loose fibrovascular stroma.

Animal No. 6 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Scattered mast cells were observed throughout the connective tissue and were particularly prominent around the vessels. Some of the skeletal muscle fibers adjacent to adipose tissue in one of the sections were slightly granular and hypereosinophilic. Acute minimal hemorrhage was observed around these myofibers, but no other inflammatory reaction was noted. Some of the adjacent vessels in the superficial lamina propria were congested with adjacent minimal acute hemorrhages also noted.

Animal No. 7 - Right Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Scattered mast cells were seen in the supporting connective tissue. A region of minimal perivascular mixed inflammation was comprised of lymphocytes, mast cells and some granulocytes accompanied by some minimal free hemorrhage. Superficial vessels in the area of inflammation were congested. Minimal cellular crusting was observed in the keratin layer overlying the area of inflammation. Inflammatory cells were also observed in the minimally spongiotic epithelium.

Animal No. 7 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Minimal congestion was observed. A few scattered mast cells were seen in the connective tissue.

Animal No. 8 - Right Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Scattered mast cells were seen in the connective tissue. A minimal amount of mucinous matrix was observed in the looser areas of connective tissue stroma. Minimal to mild congestion was observed.

Animal No. 8 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. The section with lower supporting connective tissue also contained adipose tissue and relatively attenuated bundles of skeletal muscle myofibers. Perivascular mast cells were mildly prominent.

Animal No. 9 - Right Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Scattered mast cells were observed within the connective tissue and were especially prominent around vessels. A few bronze tinted macrophages were observed in clusters in one section. The same section also had a region of superficial perivascular inflammation comprised of lymphocytes, mast cells and granulocytes, some of which were eosinophils. Superficial vessels in this area were congested. Mild vacuolation of some of the epithelial cells was observed overlying the area of inflammation. There were also a few inflammatory cells within the epithelial layer.

Animal No. 9 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Perivascular mast cells were occasionally prominent. Minimal congestion was observed. Some of the myofibers were characterized by central cytoplasmic fragmentation and intemalization of nuclei (possible artifact due to epithelial disruption at the site).

Animal No. 10 - Right Cheek Pouch

Three sections of cheek pouch were characterized by keratinized stratified squamous epithelium supported by skeletal muscle and variably dense fibrovascular tissue. Mast cells were prominent in the connective tissue and around some of the vessels.

Animal No. 10 - Left Cheek Pouch

Three sections of cheek pouch were characterized by partial natural epithelial margins of keratinized stratified epithelium supported by skeletal muscle tissue and variably dense fibrovascular tissue in which there were scattered mast cells.

SUMMARY

Minimal changes were observed in some of these cheek pouches. The majority were considered to be within normal limits. Mast cells were considered to be a normal finding in the connective tissue and may sometimes be quite prominent. The myofiber changes are attributed to sectioning or processing artifact, especially since the majority of the changes were frequently observed in areas of epithelial disruption or at the edges of the examined sections. There was generally no significant increase in epithelial thickness. Minimal focal loss of keratin, sometimes with minimal cellular crusting, was observed in focal minimal to mild regions of inflammation (for example, 4L and 5L). Minimal inflammation without significant keratin loss was also observed in some sections (for example, 3L, 4R, 7R and 9R). Minimal numbers of brown pigmented macrophages were seen in two sections (1R and 9R). Extremely sparse numbers of neutrophils were seen focally in the right cheek pouch of animal No. 2. A distinct difference between right and left cheek pouches was not noted. Five hamsters with right cheek pouch had some evidence of minimal to focally mild inflammatory cell infiltrate (1, 2, 4, 7 and 9). Three hamsters had some evidence of minimal to mild inflammation (3, 4 and 5) in the left cheek pouch. Three hamsters (6, 8 and 10) had no significant inflammation observed in either cheek pouch. A protocol and experimental design were not provided. No final conclusion can be made without group and experimental procedure information.

ADDENDUM

The histopathology report for NAmSA Lab Number 96C 21827 00 is to be used as histopathology data for NAmSA Lab Number 96C 21827 01.

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