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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 intracytoplasmic 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.

We describe a case of a solitary dermal cylindroma with focal malignant transformation. The scalp tumor measured 3 cm in greatest dimension and was successfully surgically excised. The patient has been followed up for the last two years with no recurrences. Changes of malignant transformation included loss of peripheral palisading, destruction of the hyaline sheath, areas of necrosis, and pleomorphism of nuclei with frequent mitosis. We reviewed data on 12 other reported cases of dermal cylindromas with malignant transformation. Morphologic features of both benign cylindromas and their malignant counterparts are described. The literature was reviewed regarding the controversy of the cell of origin.

Malignant lymphoma developed in the dorsum of the hand in a patient with a long-standing postmastectomy lymphedema. The tumor subsequently spread to involve skin of the forearm and arm. Growth and spread of malignant cells within the stagnant dilated lymphatics are the likely cause of the characteristic nodular dissemination of the tumor in a lymphedematous extremity, regardless of the type of neoplasm.