October 2016



Signalment (JPC # 2731574):  Age and breed unspecified dog

HISTORY:  Solitary dermal mass protruding from the lip

HISTOPATHOLOGIC DESCRIPTION: SLIDE A: Haired skin, lip:  Expanding the dermis, compressing surrounding dermal collagen and adnexa, elevating the overlying minimally hyperplastic epidermis, and extending to a single deep border is an unencapsulated, well demarcated, densely cellular neoplasm which is separated from the overlying epidermis by a narrow zone of dermal collagen which is devoid of neoplastic cells (Grenz zone).  The neoplasm is composed of round cells arranged in sheets, nests and packets separated by a fine fibrovascular stroma.  Neoplastic cells have variably distinct cell borders and moderate amounts of eosinophilic, granular cytoplasm, and toward the periphery of the neoplasm, few cells have a perinuclear pale area (hof).  Nuclei are irregularly round with variability in chromatin pattern, which range from finely stippled to dense with one usually indistinct nucleolus.  Mitotic figures average 1 per HPF.  Within the neoplasm, there is mild anisokaryosis, few scattered multinucleate cells with up to 5 nuclei, occasional single cell necrosis, and few foci of hemorrhage.  Within the superficial dermis there is minimal pigmentary incontinence and few scattered lymphocytes.

MORPHOLOGIC DIAGNOSIS:  Haired skin, lip: Plasmacytoma, breed unspecified, canine

Signalment (JPC #4076145): Husky, age unspecified.

HISTORY: Mass, right mandible near lip

HISTOPATHOLOGIC DESCRIPTION: SLIDE B: Expanding the dermis and compressing adnexa, elevating the epidermis, and extending into the subcutis and to cut borders is an unencapsulated, well-demarcated, poorly circumscribed, moderately cellular neoplasm composed of round cells arranged in sheets on a fine fibrovascular stroma, surrounded and separated by lakes of amorphous, smudgy, extracellular eosinophilic material (amyloid). Neoplastic cells have distinct cell borders, a moderate amount of eosinophilic, often vacuolated cytoplasm which often contains a perinuclear pale area (hof), a round to irregular shaped nucleus with coarsely stippled chromatin and 1-2 indistinct nucleoli. Anisocytosis and anisokaryosis are moderate; mitoses average 3 per 10 HPF. There are occasional multinucleated neoplastic cells with up to 3 nuclei, and rare intranuclear cytoplasmic invagination. Within the neoplasm are multifocal infiltrates of lymphocytes, and areas of hemorrhage. The neoplasm is separated from the epidermis by a prominent area of dermal collagen measuring up to 200 um (Grenz zone). Within and surrounding the lakes of amyloid are infiltrates of epithelioid macrophages and multinucleated giant cells with up to 27 nuclei, both Langhans type with peripheral nuclei, and foreign body type, with central nuclei.

SLIDE C (Congo red): Lakes of eosinophilic, amorphous extracellular material diffusely stain orange-red (congophilic), and exhibit apple-green birefringence under polarized light (amyloid).

MORPHOLOGIC DIAGNOSIS: Haired skin, subcutis and skeletal muscle, right mandible near lip: Plasmacytoma, with amyloid, husky, canine.

CONDITION:  Cutaneous extramedullary plasmacytoma (EMP); Plasma cell tumor




TYPICAL GROSS FINDINGS:  Tumors are usually 1 to 2 cm, raised, smooth, well circumscribed, firm to soft, and pink to red





Gross:  Similar to benign cutaneous histiocytoma




  1. Clancy CS, Roug A, Armien AG, Van Wettere AJ. Intracerebral malignant plasmacytoma in a mule deer. J Comp Pathol. 2016;154(2-3):268-71.
  2. Goldschmidt MH, Hendrick MJ. Tumors of the skin and soft tissues. In: Meuten DJ, ed. Tumors in Domestic Animals. 4th ed. Ames, IA: Iowa State Press; 2002: 113-115.
  3. Greenberg MJ, Schatzberg SJ, deLahunta A, Stokol T, Summers BA. Intracerebral plasma cell tumor in a cat: A case report and literature review. J Vet Intern Med. 2004;18:581-585.
  4. Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat, Clinical and Histopathologic Diagnosis. 2nd ed. Oxford, UK: Blackwell Science; 2005:866-872.
  5. Majzoub M, Breuer W, Platz SJ, Linke RP, Hermanns W. Histopathologic and immunophenotypic characterization of extramedullary plasmacytomas in nine cats. Vet Pathol. 2003;40:249-253.
  6. Platz SJ, Breuer W, Pfleghaar S, Minkus G, Hermanns W. Prognostic value of histopathological grading in canine extramedullary plasmacytomas. Vet Pathol. 1999;36: 23-27.
  7. Ramos-Vara JA, Miller MA, Valli VEO. Immunohistochemical detection of multiple myeloma 1/interferon regulatory factor 4 (MUM1IRF-4) in canine plasmacytoma: comparison with CD79a and CD20. Vet Pathol. 2007;44:875-884.
  8. Valli VE, Jacobs RM, Parodi AL, Vernau W, Moore PF. WHO Histological Classification of Hematopoietic Tumors of Domestic Animals, 2nd series, vol. VIII. Washington, DC: Armed Forces Institute of Pathology; 2002: 34-35.
  9. Valli VEO, Kiupel M, Bienzle D. Hematopoietic system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016: 226-8.
  10. Wettere AJ, Linder KE, Suter SE, Olby NJ. Solitary intracerebral plasmacytoma in a dog: Microscopic, immunohistochemical, and molecular features. Vet Pathol. 2009;46:949-951.

Click the slide to view.

Click on image for diagnostic series.

Back | Home | Contact Us | Links | Help |