Section 11
Chapter 10,722

Glycogen-rich malignant melanomas and glycogen-rich balloon cell malignant melanomas: frequency and pattern of PAS positivity in primary and metastatic melanomas

Nowak, M.A.; Fatteh, S.M.; Campbell, T.E.

Archives of Pathology and Laboratory Medicine 122(4): 353-360


ISSN/ISBN: 0003-9985
PMID: 9648905
Accession: 010721224

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Objective: After identifying a metastatic glycogen-rich balloon cell malignant melanoma, originally thought to be a benign clear cell tumor of the lung, we investigated the extent of positive reactions, or "positivity," of malignant melanoma to periodic acid-Schiff (PAS) staining. Methods: Frequency, intensity, and distribution of PAS positivity was studied in 61 excisional biopsy specimens from 58 patients with malignant melanoma. For comparison, 17 benign nevi from 10 patients were examined. Results: Positivity for PAS was seen in all cases. All malignant melanomas and benign nevi were characterized by weak, diffuse, diastase-resistant PAS positivity. Additionally, focal or diffuse, strong diastase-sensitive PAS positivity was observed in 9 of 61 melanomas (15%); 7 were metastatic and 2 were primary invasive melanomas. Strong diastase-sensitive PAS positivity was seen in all lesions with 30% or more balloon cell features and only in advanced primary or metastatic lesions. The presence of glycogen was confirmed by transmission electron microscopy. Conclusions: Cutaneous malignant melanomas have weak, diastase-resistant PAS positivity. Strong diastase-sensitive PAS positivity, consistent with the presence of intra-cytoplasmic glycogen, is seen in many primary and metastatic melanomas with balloon cell features. Depending on the content of the balloon cells, these melanomas are best categorized as either glycogen-rich malignant melanomas or glycogen-rich balloon cell malignant melanomas. Because many tumors with clear cell features contain glycogen, such content often is an unreliable differential feature.

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