Pulmonary Microcystic Fibromyxoma: Report of 3 Cases

Three cases of pulmonary myxoid tumors showing a variable degree of microcystic change are described. They are presented as incidental solitary peripheral lung nodules on routine radiologic studies. The patients included 2 women, 45 and 65 years old, and 1 man, 33 years old. Clinical work-up showed no evidence of neoplasia in other sites. Following surgical resection, no evidence of disease was observed after a mean follow-up of 48 months. The tumors ranged in size from 1 to 2.3 cm (mean 1.4 cm). Microscopically, the lesions were well circumscribed with conspicuous cystic change and myxoid stroma. Innocuous, widely-spaced, spindled to stellate tumor cells showed minimal nuclear pleomorphism and absence of mitotic activity. The myxoid stroma contained acid mucopolysaccharides, sensitive to hyaluronidase digestion. No epithelial, chondroid, neural, myofibroblastic, lipomatous or vascular differentiation was evident on immunohistochemical studies. Although these cases display cytologic features, myxoid stroma and benign clinical course characteristic of pulmonary myxomas; the presence of microcystic architecture is unique to the current series, and thus a descriptive designation "microcystic fibromyxoma" is suggested.