Scraping cytology in the diagnosis of malignant squamous neoplasms of the skin

cytologic examination of skin scraping material was first used in the late 1940s by Tzanck in the differential diagnosis of bullous lesions.1 However, the scraping technique found limited applications in the diagnosis of benign skin diseases.2,3 Those who have used cytologic methods for the diagnosis of skin cancer, however, have reported favorable results. This technique can be considered a rapid screening technique and may be used as an adjunct to biopsy.4 The most common use of skin scrapes currently is in the differential diagnosis of basal cell carcinoma (BCC) from squamous cell carcinoma (SCC) and of both from benign skin lesions.2,4,5 At our institute, we have applied skin scrape methods to suspected cutaneous malignant lesions on the head. The scrapings were done with a sterile blade after skin antisepsis. If thick crusts were present, they were initially abraded and discarded. Occasionally small hemorrhages occurred, but these were not severe. The procedure was not painful; local anesthesia was not required. Scrapings were transferred to a glass slide, air dried and stained with May-Gr\ufcnwald-Giemsa stain. Subsequently, punch biopsies were performed for histopathology; specimens were routinely processed. Cytologic diagnoses were categorized as unsatisfactory, negative and malignant. When possible, malignant cases were divided into subgroups BCC and SCC. The smear and tissue specimens were studied separately; diagnoses were subsequently collated. Cytologic examination revealed malignancy in 18 cases. All were histopathologically confirmed. Both cytologic and histopathologic investigations were negative in one case. Another case was unsatisfactory cytologically but malignant on histopathologic assessment. Despite being \u93unsatisfactory,\u94 this case was regarded as a false negative. The rate of false negatives was thus 1/19 (5.3%). No false positive results occurred. Of the malignant cases, eight were classified as BCC and five as SCC. No discrepancy between cytology and histopathology was found in any of the cases so categorized. The remaining five cases could not be subclassified cytologically. BCCs are the most common skin tumors encountered and can be diagnosed easily by scraping cytology if sufficient material is obtained.6 BCCs have a variable clinical appearance but, in general, present with an area of central ulceration. Cytologic examination reveals cellular smears consisting of cohesive sheets of small, hyperchromatic cells showing mild nuclear pleomorphism and crowding. The nuclei are round or oval and two to three times the size of red blood cells (Figure 1). Cytoplasm is scanty and cell borders are indistinct. Peripheral palisading is commonly seen and should be sought in groups of tumor cells forming cell balls with a smooth, rounded margin.3-5 SCCs of the skin usually occur as shallow, indurated ulcers with irregular margins or as cauliflowerlike, exophytic growths. Skin scrapes of these lesions show sheets as well as dissociated single atypical cells.4 They have moderate to abundant cytoplasm demonstrating a variety of cell shapes. Nuclei are usually hyperchromatic but sometimes vesicular, containing nucleoli (Figure 2). There are certain limitations of cytodiagnosis that may cause problems in differential diagnosis and that should be borne in mind. Flattened or ulcerated seborrheic keratosis may be confused with BCC or SCC.4 In addition, the cytologic features of premalignant lesions may show a striking resemblance to those seen in SCC. The small cell type of SCC in particular can resemble BCC. Scraping cytology may fail in crusted, hyperkeratotic and tough cutaneous lesions. In such cases, alternate methods of obtaining material for smears have been employed. 4 Despite our limited material, we can recommend scrape specimens of cutaneous lesions suspected of malignancy as a rapid and reliable diagnostic method. Furthermore, the differential diagnosis between BCC and SCC can usually be made. Bearing the limitations in mind, this method permits prompt institution of therapy