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June 2005
PAP/NGC Programs Review
Michael Henry, MD
Fine-needle aspiration of the lung is a well-established method for the initial
diagnosis of pulmonary nodules. While pulmonary hamartoma is a rare lesion,
it is the most common benign neoplasm found in the lungs. The cytologic features
of FNA of pulmonary hamartoma have been well described, but there is overlap
between these lesions and certain well-differentiated pulmonary malignancies.
With this in mind, Jonathan Hughes, MD, PhD, and colleagues used the data from
the CAP Interlaboratory Comparison Program in Nongynecologic Cytology to evaluate
the accuracy of FNA biopsy in the diagnosis of pulmonary hamartoma (Arch
Pathol Lab Med. 2005;129:19–22). These data provide a valuable resource
of information regarding diagnostic accuracy for cytologists in a wide range
of clinical practice settings. In this study, data from a six-year period were
evaluated looking at the responses to a series of 19 cases of pulmonary hamartoma.
A total of 766 separate individual participant responses were received with
a range of eight to 113 responses for each case. The participants chose the
correct general category (benign) in 598 cases (78 percent). In only one case
did all of the participants correctly classify the slide as benign. Of interest,
in only 200 (26 percent) responses did the participants make the correct specific
diagnosis of pulmonary hamartoma. An incorrect general diagnosis of malignant
was made in 168 (22 percent) of the responses. The most common incorrect specific
responses were carcinoid tumor, adenocarcinoma, and small cell carcinoma.
On review of the slides, all were found to have good cellularity, and the diagnostic
features of pulmonary hamartoma were well represented, including cartilaginous/fibromyxoid
stroma and numerous benign epithelial cells. The authors concluded that factors
that may have contributed to the incorrect diagnosis of malignant included not
recognizing the mesenchymal component on Papanicolaou stain (versus Diff-Quik)
along with overcalling the often abundant epithelial elements.
Dr. Henry, a member of the CAP Cytopathology Committee, is staff pathologist
at Cleveland Clinic Florida, Naples.
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