Reticulin immunostaining revisited

Introduction: Reticulin staining has been suggested as an inexpensive tool in the differential diagnosis of melanoma versus benign nevi. In the present study, reticulin immunostaining patterns in malignant melanomas, benign intradermal nevi, and blue nevi were observed. The concordance in evaluation of the pattern between observers was also done. Materials and Methods: A retrospective search was performed in the computer database of the Ackerman Academy of Dermatopathology for “melanoma,” “melanocytic nevus,” and “blue nevus”. Fifty-six melanomas (30 of nodular subtype and 26 of superficial spreading subtype), 54 benign compound nevi, and 27 blue nevi were selected for the study. Patterns of reticulin staining in the dermis and the basement membrane in these melanocytic lesions were evaluated and the concordance between the two groups of authors was assessed. Statistical evaluation was performed with the Statistica® 10 program, Tulsa, OK. Concordance of the pattern evaluation was evaluated using Cohen's kappa coefficient. Results: Melanomas show a variable basement membrane pattern some of which show flat, thin and smooth pattern. Benign nevi almost never showed this flat pattern at the basement membrane zone. In the dermis, melanomas showed reticulin fibers surrounding groups of melanocytic cells while nevi predominantly had reticulin fibers around individual cells. There was greater agreement in evaluating the dermal component compared to the basement membrane pattern. Conclusion: The dermal reticulin staining pattern may be of some value in the diagnosis of melanocytic lesions, but poor concordance in evaluation of the basement membrane zone pattern limits its usefulness.