PART TWO
Diagnostic Cytology
Key features of adamantinoma
• Lytic, diaphyseal tumor;
• Palisading, columnar cells;
• Bland nuclei; and
• Keratinized cells in pearl arrangements;
• High N/C ratio with fine chromatin.
• Usually clean background;
SKIN
Techniques
The most common approaches to skin lesions are punch biop-
sies and shave biopsies, but cytological methods can play an
important role by providing a fast and accurate diagnosis of
many skin diseases. Lesions with skin surface involvement can
be evaluated by scrapping or touch preparations, while lesions
forming masses can be sampled by FNAB.
Scrape cytology has been widely used to diagnose basal cell
carcinoma. Usually, a scalpel blade is used to scrape the surface
of the lesion; the material is then smeared onto a slide which
is fixed, stained, and immediately viewed under a microscope;
alternatively, the slides are air-dried and Giemsa stained or
treated with 0.1% aqueous toluidine blue for 2 minutes fol-
lowed by brief washing in water before routine dehydration,
clearing, and mounting. Variants of this technique include
the use of swabs to obtain the material, imprint cytology, and
preparing the first lesion by removing any visible crust. This
technique offers many advantages. It is a simple and time- and
cost-effective. It also provides a confirmatory diagnosis at the
initial patient visit. This could be extremely beneficial in situ-
ations where even a simple 2-mm punch biopsy may be con-
sidered inappropriate, such as in a cosmetically sensitive site
in a young person or when nonsurgical therapies are planned.
Scraping cytology can be used in lesions suspicious for basal
cell carcinoma and squamous cell carcinoma, but it should be
used with care in cases of pigmented lesions and melanoma,
which are better evaluated by tissue biopsy. Cytology cannot
provide a precise diagnosis of the different histological types
of benign melanocytic nevi, nor can it enable their differentia-
tion from dysplastic melanocytic nevi or incipient malignant
melanoma.184
FNAB is a fast, reliable, and cost-efficient technique for diag-
nosing palpable masses. However, when the lesion is small,
dermal in location, shallow in depth, or fibrotic, the cellular
yield by FNAB may be limited and thus hinder an accurate
diagnosis.185 The FNAB of skin masses can be useful in distin-
guishing benign processes from malignant neoplasms. As in any
other site, it is important to perform an adequacy assessment
in FNAB so that enough material is obtained for diagnosis and
ancillary studies, if needed. For instance, a case of Merkel cell car-
cinoma can be diagnosed with confidence on cytology material
if enough material is collected for immunohistochemical studies
and cases of leukemia cutis can be sent for phenotyping by flow
cytometry. FNAB also plays a role in the fast diagnosis of meta-
static malignancies, which can be diagnosed with ease. FNAB
may also play a role in the diagnosis of cutaneous leishmaniasis
since it is easier to perform, and takes less time to demonstrate
the organism than scrapings. Therefore, FNAB is recommended
as the method of choice in confirming the clinical suspicion of
cutaneous leishmaniasis in endemic areas. However, whenever
there are limitations in achieving an accurate diagnosis, FNAB
cannot be regarded in general as a substitute for histological
diagnosis.186-190
Non-neoplastic
Non-neoplastic Lesions
The majority of non-neoplastic lesions of the skin are infectious,
either viral or parasitic. Other conditions such as sarcoidosis
may also be encountered. It is uncommon for these lesions to
be aspirated as the clinical appearance is often diagnostic.
Those dermatologic conditions associated with blistering may
be the best suited to cytologic examination, particularly because
the fluid often present within the vesicles can be easily obtained.
It is preferential to sample the base of such lesions and to do so
in the early stages of presentation to avoid the degeneration or
secondary bacterial infection that may occur.
Blistering conditions include pemphigus vulgaris, an auto-
immune condition, which contains atypical parabasal squa-
mous cells, which are round single cells with a perinuclear halo
and a prominent nucleolus. Giant cells may be present and the
cytologic atypia seen may mimic that of a malignancy.191
infectious Conditions
Skin infections include those caused by viruses, fungi, and bac-
teria. Only viral and fungal infections have features specific
enough to allow cytologic identification. Viruses can be recog-
nized by characteristic cytopathic changes such as seen with her-
pes and cytomegalovirus. Fungus can be recognized by specific
morphology visible in cytology preparations. Neither Giemsa
nor Papanicolaou stain
can
distinguish
Gram-positive
or
-negative bacteria; therefore cytology cannot be used to subtype
bacterial infections.
Viral infections can be diagnosed based on the cytomor-
phologic effects of the virus found in fluid from the base of the
lesions using Diff-Quik, Papanicolaou stain, or H&E stain. Fea-
tures of herpes are classic and identical to those seen in cervical
vaginal specimens (Fig. 18.47). Ground-glass-appearing nuclei
with multinucleation and molding are the hallmarks of herpetic
infections.
Molluscum bodies from superficial infection with the pox
virus molluscum contagiosum are large rounded cytoplasmic
inclusions which push the cell nucleus to the periphery.192
Fungal infections are usually identified in scrape prepara-
tions with the recognition of specific morphologic features such
as hyphae and branching.
502
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