Gastric mucinous adenocarcinoma with cutaneous metastases in a dog: diagnosis by fine‐needle aspiration cytology

Abstract

A 12-year-old, intact, male mixed-breed dog was presented with anorexia, vomiting and multiple cutaneous nodules on its neck, trunk and hindlimbs. Fine-needle aspiration cytology of the nodules was characterised by a pleomorphic population of cells arranged singly or in small cohesive clusters, embedded in an amorphous mucinous material stained positive by periodic acid-Schiff (PAS). Acinar structures were occasionally found. Cells appeared either small with scant basophilic cytoplasm or large with a histiocytic appearance. Large cells had cytoplasm filled with a PAS-positive granular material. A presumptive diagnosis of cutaneous metastases of a mucinous adenocarcinoma was made. A primary, gastric, signet-ring mucinous adenocarcinoma was confirmed at postmortem examination and by histopathology. To the authors' knowledge, this is the first report of a gastric mucinous adenocarcinoma with cutaneous disseminated metastases in a dog.

Canine non-hematopoietic gastric neoplasia

“…Radiographs of the thorax did not document the presence of pulmonary metastasis in any of the cases presented in this study. This is in accordance to previous reports, and distant metastasis does not seem to be a common entity in this tumor type (3,10,30). However, there is one report on cutaneous metastases in a dog with gastric adenocarcinoma (3), distant spread -most commonly pulmonary or hepatic -of these tumors therefore is a possibility.…”

“…Only few reports exist on cytologic examination in dogs with gastric neoplasia (3,22). Rivers et al (22) report of successful ultrasound-guided fine-needle aspiration cytology in 2 out of 3 cases.…”

Use of destained cytology slides for the application of routine special stains

“…The special stains used in this study have been applied successfully for decades in human and veterinary cytology, where they have been applied directly to fresh air‐dried 8,10,11 or alcohol‐fixed 6 smears. Destaining, however, is not commonly used and only isolated reports recommend destaining slides when special stains are required, namely when no unstained smears remain or when a particular feature has been observed in a single slide 9,17 .…”

“…We demonstrated in this study that Alcian blue can also be used in destained fine‐needle aspirate smears to highlight the mucinous nature of a myxosarcoma. PAS has also been used in unstained smears, for evaluating abdominal fluid, 11 conjunctival impressions (goblet cells), 6 and in aspirates of cutaneous nodules in the dog 8 . In the latter, PAS was used to demonstrate mucus secretion, thus helping in the diagnosis of metastatic adenocarcinoma.…”

“…Histochemical methods play a major role in diagnostic pathology for confirming or reaching a diagnosis, especially in atypical infections or undifferentiated neoplasia 2 . Histochemical stains have long been applied to cytologic specimens in medical and veterinary pathology 3,4 ; several recent reports have been published that highlight the use and importance of special stains in veterinary cytology 5–11 …”