Page 1445 - Small Animal Internal Medicine, 6th Edition

CHAPTER 88 Lymphadenopathy and Splenomegaly 1417

diagnosis that was equivocal for neoplasia on both tests and by variable numbers of lymphoid cells in different stages of
therefore was not categorized. Of the 35 dogs that had diag- development (small, medium, and large lymphocytes; plasma
VetBooks.ir nostic samples, cytopathologic and histopathologic diagno- cells); hematopoietic precursors are common in dogs and
cats with splenic hyperplasia. The cytologic features of
ses agreed completely in 18 of 35 dogs (51.4%) and partially
in 3 of 35 dogs (8.6%) and were in disagreement in 14 of 35
type of reaction elicited. Causative agents can frequently be
dogs (40.0%). Pathologists collaboratively reviewed diagno- lymphadenitis-splenitis vary with the causative agent and the
ses that were in disagreement or partial agreement and identified in cytologic specimens (see Fig. 74.2). Metastatic
altered their individual diagnoses in 6 of 17 dogs (35.3%) to neoplasms have different cytologic features, depending on
be within partial or complete agreement, respectively. Percu- the degree of involvement and cell type. Carcinomas, adeno-
taneous FNA and NCB can be performed safely in dogs with carcinomas, melanomas, and mast cell tumors are easily
sonographic splenic changes. Results suggest that adding diagnosed on the basis of cytologic findings. However, the
NCB to FNA provides complementary information in dogs cytologic diagnosis of sarcomas may be difficult because the
with suspected splenic neoplasia. This combined protocol neoplastic cells that comprise this tumor do not exfoliate
may improve detection of splenic neoplasia and provide neo- easily. Primary lymphoid neoplasms (lymphomas) are char-
plastic subclassification. acterized by a monomorphic population of lymphoid cells,
In a patient with generalized lymphadenopathy, the clini- which are usually immature and show a fine chromatin
cian must decide which lymph node to aspirate. Obviously pattern, one or more nucleoli, basophilic cytoplasm, and
aspiration of a node in which the tissue changes are repre- vacuolation (Fig. 88.8). For a more detailed description of
sentative of the ongoing disease is important. Therefore a cytologic changes, see Chapter 74.
specimen should not be obtained from the largest lymph When the cytologic examination of an enlarged lymph
node because the necrosis may preclude a definitive diagno- node or spleen does not yield a definitive diagnosis, excision
sis. Because clinical and subclinical gingivitis is common in of the affected node or incisional or even excisional splenic
older dogs and cats, mandibular lymph nodes should not be biopsy to obtain a specimen for histopathologic examina-
routinely aspirated because they are usually reactive, and tion is indicated. Excision of the whole node is preferable;
findings may obscure the primary diagnosis. The techniques core biopsy specimens are difficult to interpret because the
of FNA are described in Chapter 74. lymph node architecture is often poorly preserved. A per-
Several reviews of the cytologic evaluation of lymphoid cutaneous needle biopsy of the spleen can be done under
tissues have appeared in the veterinary literature (see later, ultrasonography; alternatively, a wedge of tissue can be
“Suggested Readings”). In brief, normal lymph nodes are obtained during a splenic biopsy or, if the surgeon deems
composed primarily of small lymphocytes (80%-90% of all it necessary, a splenectomy can be performed; recently,
cells); a small number of macrophages, medium or large single-port laparoscopy-assisted splenectomy techniques
lymphocytes, plasma cells, and mast cells can also be found. have been described in dogs (Wright et al., 2016). Care
Normal spleens are similar except that RBCs are in high should be taken in handling the tissues during surgical
concentration given this organ’s vascularity. Reactive lymph
nodes (Fig. 88.7) and hyperplastic spleens are characterized

FIG 88.8
Cytologic features of a lymph node aspirate from a dog
FIG 88.7 with massive generalized lymphadenopathy (lymphoma).
Cytologic features of a reactive lymph node in a dog. Note Note a monomorphic population of large round cells with a
the heterogeneous cell population containing small, lacy chromatin pattern (neoplastic cells) intermixed with
intermediate, and large lymphocytes and abundant plasma small, darker, normal lymphocytes; lymphoglandular bodies
cells (Diff-Quik stain; ×1000). are present (Diff-Quik stain; ×1000).