Cytologic Grading of Cutaneous Sebaceous Neoplasms: Does it Help to Differentiate Benign From Malignant?

Both architectural and cytologic characteristics are used to distinguish benign from malignant sebaceous neoplasms; however, specific cytopathologic features of sebocytes have not been well defined. The authors assessed architectural and cytological features of 63 sebaceous neoplasms [15 sebaceous hyperplasias, 12 sebaceomas, 16 sebaceous adenomas (SA), 14 sebaceous carcinomas (SC), and 6 ocular sebaceous carcinoma (OSC)] to investigate whether cytological grading may facilitate classification of lesions. Among other criteria, nuclear pleomorphism (size, nucleolar appearance, membrane irregularity, crowding, mitoses, and chromatin pattern) was assessed and 3 theoretical nuclear grades established. Immunohistochemistry for CK10, p16, adipophilin and ki67 was performed on 7 cases of each type of tumor. Most sebaceous neoplasms, except OSC, showed a bland architectural silhouette. However, SA, SC, and OSC revealed larger nuclei (≥14 µm in ≥50% of cases), evident to multiple nucleoli, membrane irregularity, coarse to clumped chromatin, and nuclear grade ≥2 (latter in ≥56% of cases); by contrast, sebaceous hyperplasia and sebaceomas showed smaller nuclei (≤10 µm in ≥50% of cases), smooth borders, inconspicuous nucleoli, fine chromatin, and grade 1 nuclei (latter in 100% of cases). In the setting of a well-circumscribed architecture, cytologic features gain importance in the classification of sebaceous neoplasms. Interestingly, cytologic similarities found in SA and SC may indicate a close relationship of both neoplasms.