Splenic nodular hyperplasia

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Nodular hyperplasia of the spleen in a dog[1]

Splenic nodular hyperplasia is a benign neoplasia of the canine spleen.

These tumors are frequently found as an incidental finding but are an important differential when detecting splenic tumors.

A number of variants have been reported, including:

  • Lymphoid hyperplasia[2]
  • Hematopoietic hyperplasia
  • Plasmocytic hyperplasia
  • Fibrohistiocytic hyperplasia - early lymphoma forms[3]
  • Mixed hyperplasia

Clinically affected dos may show no symptoms or may present with a palpable splenic mass.

A presumptive diagnosis is usually established with radiographic, ultrasonographic or CT imaging[4]. A definitive diagnosis is usually achieved with ultrasound-guided percutaneous biopsy and histological examination of tissue samples[5].

Nodular fibrohistiocytic hyperplasia may represent a transitional form between nodule and malignant neoplasia (i.e., malignant fibrous histiocytoma or generalized histiocytic sarcoma) and histologically are characterized by a mixed population of spindle cells in varying proportions with hematopoietic elements, plasma cells, and lymphocytes[6].

In patients with histiocytic hyperplasia, high mitotic indices are usually afforded a guarded prognosis as these often transform into malignant lymphoma with a 12-month period in 50% of cases[7].

In other forms of splenic nodular hyperplasia, there are usually no clinical symptoms associated with this condition.

A differential diagnosis would include splenic contracture post-anesthesia, splenic tumors, splenic hematoma, mast cell tumor[8], splenitis and secondary lymphoma[9], mast cell tumor and hemangiosarcoma[10].

These tumors are usually benign apart from histiocytic forms and rarely require surgical intervention, although regular monitoring of the patient is recommended.

References

  1. University of Pennyslvania
  2. Cole PA (2012) Association of canine splenic hemangiosarcomas and hematomas with nodular lymphoid hyperplasia or siderotic nodules. J Vet Diagn Invest 24(4):759-762
  3. Spangler WL & Kass PH (1998) Pathologic and prognostic characteristics of splenomegaly in dogs due to fibrohistiocytic nodules: 98 cases. Vet Pathol 35(6):488-498
  4. Fife WD et al (2004) Comparison between malignant and nonmalignant splenic masses in dogs using contrast-enhanced computed tomography. Vet Radiol Ultrasound 45(4):289-297
  5. Day MJ et al (1995) A review of pathological diagnoses made from 87 canine splenic biopsies. Small Anim Pract 36(10):426-433
  6. VSSO.org
  7. Moore AS et al (2012) Histologic and immunohistochemical review of splenic fibrohistiocytic nodules in dogs. J Vet Intern Med 26(5):1164-1168
  8. Book AP et al (2011) Correlation of ultrasound findings, liver and spleen cytology, and prognosis in the clinical staging of high metastatic risk canine mast cell tumors. Vet Radiol Ultrasound 52(5):548-554
  9. Eberle N et al (2012) Splenic masses in dogs. Part 1: Epidemiologic, clinical characteristics as well as histopathologic diagnosis in 249 cases (2000-2011). Tierarztl Prax Ausg K Kleintiere Heimtiere 40(4):250-260
  10. Rossi F et al (2013) Metastatic cancer of unknown primary in 21 dogs. Vet Comp Oncol Jan 7