Microcystic squamous cell carcinoma of the lung: a clinicopathologic study of three cases.

Three cases of pulmonary squamous cell carcinoma (SCC) are described displaying a prominent microcystic pattern closely resembling microcystic adnexal carcinoma of the skin (MAC). The patients were 2 women and 1 man aged 72 to 83 years. Histologically, in addition to conventional SCC, all tumors showed striking microcystic changes characterized by nests and strands of basaloid squamous cells with central cystic spaces, peripheral palisading, and cytoplasmic clearing of the central tumor portions. Follow-up available for 2 patients revealed that 1 was alive at 76 months and 1 had died 38 months after diagnosis. Microcystic SCC is an unusual variant of SCC of the lung histologically mimicking tumors with glandular or adnexal differentiation and a particularly striking resemblance to MAC of the skin. The importance of the recognition of this growth pattern lies in the separation from other often less aggressive pulmonary neoplasms or metastatic disease from a cutaneous tumor.