If you are an average Canadian small animal veterinary practice, you will submit samples from3 cases perveterinarian per month for histologic evaluation. Because of expense, risk, or owner reluctance,surgicalbiopsy often is the last diagnostic strategy to be employed and thus there often are a lot ofexpectationsimposed upon these samples. There is nothing I dislike more than to issue a report of "unsuitablesample"or "nonspecific, end-stage lesion" that will be a waste of your efforts and your client's money, andmayresult in delay of appropriate medical or surgical therapy.

How come the results didn't meet your expectations?

1. Too little too late
     The most common cause for disappointment is unduly high initial expectation. A commonscenario, for example, is the single biopsy from a dog with two years of chronic dermatitis, treatedwithevery drug and prayer known to humanity. Finally you convince them to spring for biopsy, andexpect meto solve the mystery! (Does this sound familiar??) Remember the golden rule: for everyinflammatorydisease in every body system, the specificity of lesions fades rapidly with the passage of time.Iknow it is difficult to convince owners, but you should press for biopsy early in thecourse of any diseasethat is not clinically typical or does not respond appropriately to reasonable therapy.

2. Unsuccessful biopsy technique
     Particularly with biopsies that are infrequent, like biopsies from bone, turbinates, nailbed oresophagus, the sampling frequently fails to capture the critical tissue. With bone tumors, forexample, theerror is one of inadequate depth and inappropriate instrumentation. When contemplatingbiopsy of anunfamiliar tissue or for an unfamiliar disease, call your favorite pathologist to ask what kind ofsample is optimal.

3. We don't know!
     Everybody makes mistakes in interpretation, but more often there is simply inadequateinformation about the disease to allow for any reliable interpretation. With intestinal biopsies, forexample, nobody knows how many leucocytes are found in the intestinal lamina propria of normaldogsor cats. The entire myth of inflammatory bowel disease is therefore built upon feet of sand. In asimilarvein, nobody knows how many eosinophils are "too many" in a feline bronchial aspirate. Theseannoyingpuddles of ignorance have been left behind in our rapid march forward into molecular biology andhightechnology, and rarely do we admit to these surprisingly frequent gaps in what would seem likeimportantareas of clinical medicine.

SPECIFIC BIOPSY SITUATIONS: MAXIMIZE YOUR CHANCES

Inflammatory skin disease:

Indications: Poor response to initial therapy, weird lesions right fromthe start, lesionssuspicious of a very serious disease, demanding or cynical client.

Technique: Sample selection much more critical than biopsy size. Sample everyvariation ofactive lesion that you can find, within the limits of humane practice. If you think certainlesions areperhaps a different disease, submit them in a separate container. Average case should yield 3-4biopsies.

Reasons for failure: Randomly selected biopsies from chronic disease,biopsies taken within 10days of the end of steroid therapy, expectation that anyone can prove the presence ofallergic skindisease.

Cutaneous or subcutaneous lumps:

Indications: Rapid growth, infiltrative growth, bad location, anxiousowner.

Technique: Needle aspiration, core, incision, excision. Excision is always themost suitable fordiagnosis and especially for prognosis. One possible exception is investigation of lymph nodeenlargement, because fine needle aspiration is probably as good as any technique for confirmingsuspected malignant lymphoma. Tru-cut samples are under-utilized and usually are superior to fineneedleaspiration for other types of lumps if complete excision is not an immediate option.

Reasons for failure: Expectation of precise tumor identification with anythingother thanexcisional biopsies, expectation that we can determine completeness of excision of invasivetumors, oraccurate identification of truly aggressive, anaplastic tumors (anaplastic, by its very definition,means thatthe tumor is so primitive that even the tumor cells themselves do not remember whothey are!).

Nasal biopsies:

Indications: Refractory rhinitis, suspected mycotic rhinitis, suspectedneoplasia.

Technique: Nasal swabs, nasal flushes, traumatic flushes, blind biopsies,endoscopically-guidedbiopsies. Everybody gets lucky once in a while, but only endoscopically-guided tissue biopsiesroutinely provide useful results. Chunks of tissue "sneezed out" are probably next best, and nasalswabs for cytology are almost useless.

Reasons for failure: Almost all attempts at nasal cytology; tissue biopsy notaided by visualization of abnormal tissue.

Gastrointestinal biopsies:

Technique: Endoscopic mucosal biopsies, exploratory surgery, rigidproctoscopy.

Reasons for failure: Failure to elect procedure best suited to the diseasesuspected. Endoscopy provides shallow biopsies that are difficult to interpret with respect tomalignancy. Full-thickness samples usually are very limited in number and thus risk samplingerror, and rigid scopes allow only distal colonic sampling. Expect marked variation ininterpretation of inflammatory bowel disease from different pathologists!

Other biopsies:

Muscle: For suspected immune myopathy, take many small samples instead ofone large piece. Lesions often are very spotty and false negative results arefrequent.

Bone: For suspected bone tumors, by far the biggest problem is inadequatedepth of sample. These areterribly traumatic, bloody biopsies and it is tempting to stop before your core punch reaches theactualtumor which corresponds to the lytic area on the radiograph.

Laparotomy: Really a separate topic in itself, but the rule is to sampleeverything you can safely sample.Do not rely on your ability to distinguish fatty liver from diffuse lymphoma, splenicnodular hyperplasiafrom hemangiosarcoma, or harmless reactive serosal mesothelium from implanted cancer!

Liver: Since the advent of ultrasound-guided liver core biopsies, the number ofwedge biopsies obtainedvia exploratory surgery has fallen dramatically. Nonetheless, core biopsies cannot evaluatediseasescharacterized by macroscopic changes in hepatic architecture, and will miss diagnoses likecirrhosis, somecases of shunting, hepatoma and nodular hyperplasia, and focal inflammatory diseases. In myopinion, fineneedle aspiration of liver should be more-or-less restricted to strengthening your suspicions offelinehepatic lipidosis, diffuse inflammatory disease, or hepatic lymphoma.

Kidney: In my opinion, there is rarely indication for any type of kidney biopsy indogs or cats. Careful