Tumors of the Alimentary Tract

Neoplasia is common in pet dogs but accurate figures for the incidence of tumours in this, as in other species, are sparse. The purpose of this study was to document the occurrence of tumours in a defined population of dogs. From a database of 130,684 insured dogs, claims relating to the investigation or treatment of tumours or tumour-like lesions during a 12-month period were accessed and followed up. A total of 2,546 claims were tumour related and were classified according to tumour site and type. Because the demographics of the insured population were skewed towards younger animals, a standard population, as described in the veterinary literature, was used in the calculation of tumour incidence rates. The skin and soft tissues were the most common sites for tumour development, with a standardised incidence rate of 1,437 per 100,000 dogs per year, followed by alimentary (210), mammary (205), urogenital (139), lymphoid (134), endocrine (113) and oropharyngeal (112). Canine cutaneous histiocytoma was the most common single tumour type, with a standardised incidence rate of 337 per 100,000 dogs per year, followed by lipoma (318), adenoma (175), soft tissue sarcoma (142), mast cell tumour (129) and lymphosarcoma (114). These data are unique and provide a valuable basis for future research into the aetiology and epidemiology of canine tumours.

Salivary gland tumours are a relatively rare and morphologically diverse group of lesions. Although most clinicians and pathologists will have encountered the more common benign neoplasms, few have experience of the full range of salivary cancers, which are best managed in specialist centres. This review considers some current areas of difficulty and controversy in the diagnosis and management of these neoplasms. The classification of these lesions is complex, encompassing nearly 40 different entities, but precise classification and terminology is essential for an accurate diagnosis and for the allocation of tumours to prognostic groups. For many salivary tumours diagnosis is straightforward but the wide range of morphological diversity between and within tumour types means that a diagnosis may not be possible on small incisional biopsies and careful consideration of the clinical and pathological features together is essential. Although tumour grading is important and helpful, it is not an independent prognostic indicator and must be considered in the context of stage. Large malignancies tend to have a poor prognosis regardless of grade and even high-grade neoplasms may do well when they are small. A helpful guide to management of salivary cancers is the '4 cm rule'.

Surgical resection is the primary treatment modality for colorectal cancer, and the pathologic assessment of the resection specimen provides data that is essential for patient management, including the estimation of postoperative outcome and the rationale for adjuvant therapy. The essential elements of the pathological assessment of colorectal cancer resection specimens include the pathologic determination of TNM stage, tumor type, histologic grade, status of resection margins, and vascular invasion. The prognostic and/or predictive value of these elements, as well as guidelines for their derivation and interpretation, are reviewed in detail. Other tissue-based prognostic factors that are strongly suggested by existing data to have stage-independent prognostic value or to predict response to adjuvant therapy but that have not yet been validated for routine patient care are also reviewed. These include perineural invasion, tumor border configuration, host immune response to tumor, and molecular features such as microsatellite instability or loss of heterozygosity of chromosome 18. The need for high-quality, reproducible pathologic data in the care of the colorectal cancer patient, and the dependence of that data on standardization of all aspects of pathological assessment, is emphasized.