Page 750 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

728 PART IV Specific Malignancies in the Small Animal Patient

diffuse with a varied presentation. 585,587 In decreasing order of
likelihood, lesions may include erythematous patches, alopecia,
scaling, dermal nodules, or ulcerative plaques. Nasal hypopigmen-
VetBooks.ir tation, miliary dermatitis, and mucosal lesions are rarely observed.
Peripheral lymphadenopathy may also be present. In most cats,
the duration of signs will be prolonged, lasting several months.
Cutaneous lymphoma often affects the head and face and is
generally an indolent disease. Two forms have been distinguished
histologically and immunohistochemically. Most reports in the cat
are epitheliotropic and consist of T cells, although, unlike in dogs,
adnexal structures are often spared. A report of nonepitheliotropic
cutaneous lymphoma in cats also found 5 of 6 cases to be of T-cell
derivation. 588 “Cutaneous lymphocytosis,” an uncommon dis-
ease histologically resembling well-differentiated lymphoma, was
characterized in 23 cats. 502 Solitary lesions were most common.
All were composed primarily of T cells, with two-thirds having
some B-cell aggregates. Cutaneous lymphocytosis was character-
ized as a slowly progressive disorder; however, a few cases went
on to develop internal organ infiltration. Two case reports exist
of cats with cutaneous T-cell lymphoma and circulating atypical
lymphocytes. 589,590 The circulating cells were lymphocytes with
large, hyperchromatic, grooved nuclei, and one case was immu-
nophenotyped as a CD3/CD8 population. In humans, cutaneous
T-cell lymphoma with circulating malignant cells is termed Sézary
syndrome.
For cats suspected of cutaneous lymphoma, dermal punch
biopsies (4–8 mm) should be taken from the most representative
and infiltrative sites, while avoiding overtly infected skin lesions.
Immunophenotypic and PARR analysis are often helpful in defin-
itive diagnosis. Complete staging to rule out systemic disease is
also recommended for cats with cutaneous lymphoma, as local • Fig. 33.18 Subcutaneous lymphoma of the tarsus in a cat. (Image cour-
therapy may be applied in cases of solitary disease. tesy Dr. Samuel Hocker.)
Very little has been published regarding the treatment of cuta- Most animals are otherwise healthy (substage a) and the dis-
neous lymphoma in cats 585 ; however, a report of a CR to lomus- ease is generally confined to the local site at presentation (stage
tine exists. 591 Cats with a solitary disease could theoretically be I), although in one report the tarsal location was associated with
treated with surgical excision or RT, although clinical staging is regional popliteal lymph node involvement in nearly 20% of
necessary to rule out possible further systemic involvement. For cases. 592 In two cases, concurrent feline injection-site sarcoma
multiple sites, combination chemotherapy should be considered. (FISS) was found at other sites. SC-L has several similarities to
FISS, including clinical presentation, site of occurrence, poor
Subcutaneous Lymphoma demarcation, central necrosis and peripheral inflammation,
although macrophages with phagocytized vaccine-like product has
Recently several retrospective compilations of a subcutaneous not been observed within the inflammatory component. 431 These
form of lymphoma (SC-L) have been reported. 431,592,593 Although similarities suggest the possibility that injection-site inflammation
these have been referred to as “cutaneous” lymphoma in some may play a role in the disease etiology; however, this has not been
reports, their clinical and histologic characteristics imply a SC confirmed. Regardless, SC-L should remain an important differ-
localization. Most affected cats are older DSH cats, and males may ential in consideration of FISS.
be overrepresented. Overall, this appears to be an uncommon pre- The treatment of SC-L in the literature is varied and, as such,
sentation, representing 0.4% of all cutaneous/SC masses submit- a standard of care is not currently established. 431,592,593 Although
ted in a report of 97 cases. 431 Retroviral (FeLV/FIV) antigenemia the disease is initially confined to the local primary site in most
is rare, although in one report of 17 cats, FeLV gp70 and/or p27 cases, recurrence after local therapy, whether surgical excision, RT,
protein was expressed in the majority of tumor tissues. 593 or both, occurs in nearly half of cases and eventual distant metas-
Cats with SC-L are presented with firm, painless SC nodules tasis occurs in one-third of cases. Approximately 75% of affected
with a predilection for lateral thoracic, lateral abdominal wall, cats go on to die of their lymphoma; therefore SC-L should be
intrascapular, and tarsal locations (Fig. 33.18). Histologically, they considered to have an aggressive biologic behavior. In the largest
are characterized by deep SC invasion with a monomorphic round report, median progression-free and overall STs after primary site
cell population, extension into underlying tissues and overlying surgical removal were 101 days and 148 days respectively. 431 In
superficial tissue (but not epitheliotropic), and with extensive cen- the case of tarsal SC-L, even with hindlimb amputation in three
tral necrosis and peripheral inflammation (“collaring”). Angiocen- cats, regional nodal or distant involvement was documented in all
tricity and angioinvasion are often observed. Mitotic index ranges cases (at 56, 350, and 525 days), albeit durable disease-free inter-
from 3 to more than 25/10 HPF. The round cell population has vals were observed in two cats. In a limited number of cats treated
been characterized as a large high-grade B cell in approximately with RT, responses were brisk, but some progressed beyond the
two-thirds of cases and high-grade T cell in one-third, with an radiation field. The efficacy of chemotherapy is currently not
occasional NK immunophenotype reported. 431,592,593 well known; in a small number of cases receiving a variety of