Cutaneous Malignant Mixed Tumor With Pulmonary Metastasis: A Case Report and Literature Review.

Background: Cutaneous malignant mixed tumor (MMT) is a rare sweat gland-derived tumor characterized by admixed malignant epithelial cells and chondromyxoid stroma. Approximately 50 cases have been described in the literature. Metastasis, which may occur in more than one-third of cases, is most common in the lung.

Methods: We summarized the clinicopathologic features of a patient with cutaneous MMT metastatic to the lungs. A literature review of similar cases was completed using Web of Science, Scopus, and PubMed databases.

Results: A woman in her 70s presented with an enlarging mass on her left eyebrow; histopathologic examination showed large islands of atypical cells with increased mitotic activity, admixed with necrosis on a background of fibrotic and chondromyxoid stroma. Multiple lung nodules were identified during follow-up. Examination of a pulmonary core needle biopsy specimen was consistent with metastatic cutaneous MMT. Literature review identified 10 cases published between 1980 and 2017. Most primary tumors were large (≥4 cm). Local recurrence was uncommon, and the lung was the only metastatic site in 5 cases. Histopathologically, metastatic tumors were described as more cellular, with diminished stromal tissue compared with the primary lesion.

Conclusion: This is 1 of the 11 reports of cutaneous MMT with metastasis to the lungs found in the English-language literature published after 1980. Of note, most reports were published before 1990, making this case study one of the few contemporary descriptions of cutaneous MMT with pulmonary metastases. We think that the present case report will increase the awareness of this rare tumor.