Pituitary adenocarcinoma

From Dog
Postmortem appearance of a canine pituitary adenocarcinoma[1]

Pituitary adenocarcinoma and chromophobe carcinoma are relatively rare metastatic pituitary neoplasms of younger dogs[2].

Pituitary tumors account for approximately 15% of intracranial tumors[3].

Unlike benign pituitary adenomas, pituitary adenocarcinomas are usually endocrinologically-inactive ('silent') and rapidly growing tumors with a high mortality index. Some may secrete sex hormones[4].

Metastases to distant organs may result in gastric carcinoma and renal cell carcinoma.

Localized invasion of the sella turcica, ventricles and leptomeninges is common.

Clinically affected dogs present with neurological symptoms, anorexia and rapid clinical deterioration.

Blood tests may reveal low serum gonadotropin, LH, FSH and testosterone levels but are otherwise unrewarding[5]. A low- and high-dose dexamethasone suppression tests may be used as a preliminary test for differentiating pituitary-dependent hyperadrenocorticism from adrenal-tumor hyperadrenocorticism[6].

A tentative diagnosis can be established with cranial imaging using CT or MRI[7][8], but a definitive diagnosis requires histopathological analysis of biopsies obtained via hypophyseal biopsy or exploratory craniotomy[9].

A differential diagnosis would include distemper, lymphoma, hypothalamic-pituitary trauma[10], dorsally expanding cysts, inflammatory granuloma, lymphocytic hypophysitis[11], congenital malformations such as empty sella syndrome and neoplasms such as infundibuloma, neurofibrosarcoma, xanthogranuloma, craniopharyngioma, oligodendroglioma, pituitary adenoma[12] and metastatic tumors such as metastatic mammary carcinoma, lymphoma[13], malignant melanoma and pancreatic carcinoma.

Salvage hypophysectomy may provide resolution of symptoms, but survival rates in reported cases is poor[14].

References

  1. Uni of Pennsylvania
  2. Pollard RE et al (2010) Cross-sectional imaging characteristics of pituitary adenomas, invasive adenomas and adenocarcinomas in dogs: 33 cases (1988-2006). J Vet Intern Med 24(1):160-165
  3. Melmed S (2003) Mechanisms for pituitary tumorigenesis: the plastic pituitary. J Clin Invest 112(11):1603–1618
  4. Hill KE et al (2005) Secretion of sex hormones in dogs with adrenal dysfunction. J Am Vet Med Assoc 226(4):556-561
  5. Sato J et al (2001) Pituitary chromophobe carcinoma with a low level of serum gonadotropin and an aspermatogenesis in a dog. J Vet Med Sci 63(2):183-185
  6. Feldman EC et al (1996) Use of low- and high-dose dexamethasone tests for distinguishing pituitary-dependent from adrenal tumor hyperadrenocorticism in dogs. J Am Vet Med Assoc 209(4):772-775
  7. Kraft SL et al (1997) Retrospective review of 50 canine intracranial tumors evaluated by magnetic resonance imaging. J Vet Intern Med 11(4):218-225
  8. Zhao Q et al (2010) Dynamic contrast-enhanced magnetic resonance imaging of canine brain tumors. Vet Radiol Ultrasound 51(2):122-129
  9. Platt SR et al (2002) Comparison of fine-needle aspiration and surgical-tissue biopsy in the diagnosis of canine brain tumors. Vet Surg 31(1):65-69
  10. Foley C et al (2009) Hypothalamic-pituitary axis deficiency following traumatic brain injury in a dog. J Vet Emerg Crit Care (San Antonio) 19(3):269-274
  11. Meij BP et al (2012) Lymphocytic hypophysitis in a dog with diabetes insipidus. J Comp Pathol 147(4):503-507
  12. Goossens MM (1994) Diabetes insipidus in a dog with an αMSH-producing pituitary tumor. Vet Q 16(1):61
  13. Nielsen L et al (2008) Central diabetes insipidus associated with primary focal B cell lymphoma in a dog. Vet Rec 162(4):124-126
  14. Gestier S et al (2012) Silent pituitary corticotroph carcinoma in a young dog. J Comp Pathol 146(4):327-331