Page 772 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

750 PART IV Specific Malignancies in the Small Animal Patient

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A B

• Fig. 33.32 Examples of oral solitary plasmacytoma in dogs; one involving the maxilla (A), the other involv-
ing the underside of the tongue (B). Both dogs were cured after surgical excision.

Pathology and Natural Behavior of Solitary History and Clinical Signs of Solitary and
and Extramedullary Plasmacytic Tumors Extramedullary Plasmacytic Tumors
Cutaneous and oral EMP in dogs are typically benign tumors that Clinical signs associated with EMPs and SOPs relate to the loca-
are highly amenable to local therapy. 783,851,853,862,872 There exists, tion of involvement, or in those rare cases with high levels of M
however, an uncommon form of multiple cutaneous plasmacyto- component, HVS may occur. Most cutaneous plasmacytomas are
mas in the absence of MM referred to as cutaneous plasmacytosis solitary, smooth, raised pink, variably alopecic nodules from 1 to
in dogs that is a biologically aggressive disease with treatment and 2 cm in diameter (see Fig. 33.31), although tumors as large as
outcomes more like MM. 850,873,874 Three dogs with multiple oral 10 cm have been reported. Combining large series, greater than
plasmacytomas have been reported. 871 These were locally aggres- 95% occur as solitary masses and less than 1% occur as part of a
sive but did not metastasize and these dogs enjoyed long-term sur- systemic MM process. 774,98–861,873,874 Cutaneous and oral EMPs
vival after surgical excision. usually have a benign course with no related clinical signs.
The natural behavior of noncutaneous/nonoral EMP appears Cutaneous plasmacytosis, however, is associated with multiple
to be somewhat more aggressive in the dog. Gastrointestinal EMP lesions, often with more than 10 and up to hundreds of lesions. 850
have been reported on a number of occasions in the veterinary lit- Some are ulcerated on presentation, but 81% were asymptomatic
erature, including the esophagus, 870 stomach, 874–877 and small 877 at presentation. Gastrointestinal EMPs typically have nonspecific
and large intestine. 876–880 Metastasis to associated lymph nodes signs which may suggest alimentary involvement. One dog with
is more common in these cases; however, bone marrow involve- GI EMP was presented with intussusception. 878 Colorectal plas-
ment and monoclonal gammopathies are less commonly encoun- macytomas often cause rectal bleeding, hematochezia, tenesmus,
tered. Colorectal EMPs tend to be of low biologic aggressiveness, and rectal prolapse. 879 One case of ataxia and seizure activity in a
and most do not recur after surgical excision. 879 Conversely, the dog with EMP secondary to tumor-associated hypoglycemia has
majority of SOPs eventually progress to systemic MM; however, been reported. 830 SOP is usually associated with pain and lame-
the time course from local tumor development to systemic MM ness if the appendicular skeleton is affected or neurologic signs if
may be many months to years. 797,881 SOPs have been reported in vertebral bodies are involved.
the dog involving the appendicular skeleton, as well as the zygo-
matic arch, and ribs. 797 Diagnosis for Solitary and Extramedullary
SOPs are less common in cats, and fewer reports exist in the
literature. 771,785,882–886 They occur in older cats (mean ages 9–14 Plasmacytic Tumors
years), with no significant sex predilection. The skin is the most The diagnosis of SOP and EMP usually requires tissue biopsy or
common site; however, other sites include the oral cavity, eye, GI needle aspiration cytology for diagnosis. Cells making up soli-
tract, liver, subcutaneous tissues, and brain. Reports exist of cuta- tary plasmacytic tumors in both cats and dogs have been histo-
neous EMP in cats that progressed to systemic MRD. 771,785,886 logically classified into mature, hyaline, cleaved, asynchronous,